THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 OF CALIFORNIA 
 
 PRESENTED BY 
 
 PROF. CHARLES A. KOFOID AND 
 MRS. PRUDENCE W. KOFOID 
 
 nouxnr UBRAIT 
 
THE PARASITES OF MAN. 
 
THE 
 
 PARASITES OF MAN, 
 
 AND THE DISEASES WHICH PROCEED 
 FROM THEM. 
 
 A TEXT-BOOK FOR STUDENTS AND PRACTITIONERS. 
 
 BY 
 
 RUDOLF LEUCKART, 
 
 
 
 PROFESSOR OF ZOOLOGY AND COMPARATIVE ANATOMY IN THE UNIVERSITY OF LEIPZIG. 
 
 TRANSLATED FROM THE GERMAN, WITH THE CO-OPERATION 
 OF THE A UTHOR, . 
 
 BY 
 
 WILLIAM E. HOYLE, M.A. (OXON.), M.R.C.S., F.R.S.E. 
 
 NATURAL HISTORY OF PARASITES IN GENERAL 
 
 SYSTEMATIC ACCOUNT OF THE PARASITES INFESTING MAN. 
 
 Protozoa Cestoda. 
 
 EDINBURGH: 
 
 YOUNG J. PENTLAND. 
 
 1886. 
 
EDINBURGH : PRINTED FOR YOUNG J. PENTLAND BY SCOTT AND FERGUSON 
 AND BURNESS AND COMPANY, PRINTERS TO HER MAJESTY. 
 
AUTHOR'S PREFACE. 
 
 WHEN my permission was asked to publish a Translation of my Work 
 upon Parasites, which was just then appearing in a Second German 
 Edition, I was the more ready to grant the request, since the branch 
 of Science of which it treats is one which has been cultivated more 
 especially upon German soil and by German investigators, but has 
 by no means found in other countries such wide-spread attention as 
 its great scientific and practical importance render desirable. It is 
 true that English Literature possesses in the Translation of Kiiehen- 
 ineister's Work on Human Parasites, and in the Treatises of Cobbold 
 (Entozoa and Parasites of Man), writings which cover the same ground 
 as my own ; but Kuchenmeister's work is entirely out of date, while 
 Cobbold aims at giving a general sketch rather than a complete* 
 delineation of the group. 
 
 This, however, is the aim which I have kept in view in the 
 compilation of my book. 
 
 I have endeavoured to serve the interests both of the Physician 
 and the Hygienist, as well as of the Zoologist the interests of practice 
 and of theory, which are by no means so diverse as at first sight 
 might appear. 
 
 The relations which obtain between Parasites and their hosts are 
 in all respects conditioned by their natural history; and without a 
 detailed knowledge of the organization, the development, and the mode 
 of life of the different species, it is impossible to determine the nature 
 and extent of the Pathological conditions to which they give rise, and 
 to find means of protection against these unwelcome guests. 
 
 Even small and apparently isolated facts become often of great 
 significance in this connection, and hence the Physician cannot afford 
 
 M372271 
 
VI AUTHOR S PREFACE. 
 
 to neglect matters which at first sight appear further removed from 
 his department than from that of the Zoologist. 
 
 But just as little is it permissible for the latter to forget that the 
 knowledge of the life-history of animals, after which he strives, is to 
 be obtained by the investigation not only of their organization and 
 development, but also of the position which each species occupies in 
 the economy of Nature, in the present instance of the attitude which 
 the Parasite assumes towards its host. 
 
 But few decades have passed since the full extent and the 
 significance of these relationships have been made clear to us. It was 
 only with the introduction of Helminthological experiment that a 
 new path was opened to the field of knowledge, and we Zoologists 
 gratefully recognise that the first impetus to the brilliant discoveries 
 which our science has to show was the work of a Physician, and we 
 rejoice that at the present day Medicine takes an active part in the 
 prosecution of these studies. This partnership in the work ensures 
 further progress in the future, which is the more important, since 
 our knowledge of the Parasites of Man in particular has in no respect 
 reached a satisfactory condition. Numerous weighty questions still 
 await their final solution. 
 
 As to the part which I have personally taken in the cultivation 
 of the science, it may be passed over with the remark that I have 
 devoted my labours to it for a period of more than thirty years. If 
 my efforts have in many respects been crowned with success, I owe it 
 mainly to the long period during which I have followed up the 
 solution of the problems in hand. The number of animals used for 
 Helminthological experiments amounts to many hundreds, and much 
 larger is the sum of the Parasites investigated. 
 
 What I offer to my readers, then, is the result of a prolonged and 
 minute investigation, and my work contains little which does not rest 
 upon the basis of personal observation. 
 
 Although my book is devoted mainly to the Entozoa infesting 
 Man, it offers an almost complete survey over the present state of 
 that part of Zoology which treats of Parasites. The first section 
 
AUTHOE S PREFACE. Vll 
 
 contains a general natural history of these remarkable animals, 
 intended to give a clear exposition of the phenomena of Parasitic 
 life in its various forms, as well as to narrate the history of our 
 knowledge of them. And similarly there is prefixed to the special 
 account of the various species a general sketch of the structure and 
 life-history of the groups to which they belong. This course was 
 adopted not only for purely scientific reasons, not only in order that 
 the individual facts might be fully treated in connection with related 
 phenomena, but also because by this means alone was it possible to 
 supply, by well-grounded hypothesis and inductive reasoning, the 
 gaps in our experience. The basis of our knowledge must be as 
 extensive and as profound as possible, in order that the origin and 
 nature of Parasites may be treated clearly and satisfactorily. 
 
 By this mode of dealing with the subject I hope to have met the 
 wants of those who are actuated by no interest in the Parasites of 
 Man in particular. Here I refer chiefly to the Veterinary Surgeon 
 and Cattle Breeder, who, in a summary of all that is known regarding 
 the life-history of Parasites, will find the means of becoming more 
 closely acquainted with those specially important Entozoa of our 
 Domestic Animals which also infest Man. 
 
 In leaving out of consideration the Therapeutic treatment of 
 Parasitic Diseases, I have followed the advice of one of our greatest 
 medical authorities, and I did so the more readily, since, owing to the 
 lack of personal experience in this matter, I could only have re- 
 capitulated the works of others. Correspondingly greater prominence 
 has, however, been given to those Hygienic principles which the study 
 of Parasites gives us for the protection of society and its material 
 interests, and which demand the more attention since they have 
 hitherto been insufficiently practised. It is in this connection that 
 the importance of modern Helminthology is most conspicuous ; for 
 nowhere is it more true that " prevention is better than cure," than in 
 the case of Parasitic Diseases. It is sufficient to point, by way of 
 illustration, to the Hydatid Tumours, Liver-Rot, and Trichinosis. 
 
 In spite of the importance attributed to the medicinal aspects of 
 
viii AUTHOR'S PREFACE. 
 
 the question, it was no part of my plan to make the book into a 
 collection of Pathological curiosities by the detailed narration of 
 numerous cases. Those who desire such a record are referred to the 
 pages of Davaine, " Traite* des entozoaires et des maladies vermineuses," 
 a work which only partially justifies its title, since the Zoological 
 portion is very incomplete, and by no means up to the level of our 
 present Helminthological knowledge. 
 
 In conclusion, I must point out that the earlier sheets of the 
 German Edition of this volume have already been published six years, 
 in the course of which investigation has been active, and much has 
 been added to our sum of knowledge. Whilst revising the present 
 translation, I have striven, by the addition of notes and by modifica- 
 tions of the text, to give an account of this progress, and hope that 
 nothing of importance has been omitted. 
 
 In the original compilation of this work I thought primarily of 
 Gennan readers, and hence it bears throughout traces of its origin. 
 But the quiet activity of the man of science is everywhere a portion 
 of the universal work of that spirit whence the history of culture 
 took its origin, and so may my book for the profit of the whole pass 
 over the bounds of its home, and win for itself new friends in other 
 lands ! 
 
 In conclusion, it affords me very great pleasure to express my 
 hearty thanks to Mr. W. E. Hoyle, the Translator of my work, for the 
 conscientious and in every way satisfactory manner in which the 
 English Edition has been prepared. 
 
 RUDOLF LEUCKAKT. 
 
 LEIPZIG, September 1886. 
 
TRANSLATOR'S PREFACE. 
 
 THE present translation was undertaken, in the first instance, by my 
 friend and former colleague Mr. F. E. Beddard, who found, on his ap- 
 pointment to the Prosectorship of the Zoological Society, that his 
 leisure was insufficient to allow of his completing the work, and 
 therefore made the proposal that I should carry it forward. The 
 manuscript which he .had already prepared was handed to me, and 
 contained an admirable rendering of the first half-dozen sheets, which, 
 with few modifications, is here reproduced. 
 
 As regards my own share of the work, but little needs to be said : 
 not even those reviewers who so persistently, and in many cases so 
 reasonably, decry the translation of German text-books, will require 
 an apology for an attempt to render more widely known in this 
 country a work which has long since attained the rank of a classic in 
 its native land. 
 
 No pains have been spared to present the English reader with a 
 faithful rendering of the original ; and the supervision which the 
 Author has exercised over the proof-sheets not only furnishes a 
 guarantee that he has not been misrepresented, but has also rendered 
 it unnecessary for me to do anything in the way of bringing the work 
 up to the times. A number of passages which in the course of time 
 had become antiquated were cut out by the Author, who also supplied 
 other paragraphs containing the results of more recent researches. 
 These have all been placed in brackets, and are followed by the initials 
 of the Author. The few additional remarks which I have thought it 
 necessary to make are in all cases indicated by my own initials. 
 
x TRANSLATOR'S PREFACE. 
 
 Thanks to the writings of Cobbold and others, our language 
 already possesses equivalents for most of the technical terms in this 
 work, but it has always appeared to me that it would be very 
 desirable to distinguish between the transference of a parasite from 
 one host to another, and its movement from one organ to another in 
 the same host. Hitherto the word " migration " has been used in both 
 these senses, but in the present work I have confined it entirely to 
 the former signification, and adopted " wandering " to express the 
 passage from one organ to another. 
 
 The Second Volume of the original is now being revised by the 
 Author, preparatory to the issue of a new edition; he has kindly 
 undertaken to forward the proof sheets of this for translation, so that 
 the English version may pass through the press pari passu with the 
 German, and be published simultaneously with it. 
 
 In conclusion, I must fulfil the pleasant .duty of expressing my 
 great indebtedness to my friend Mr. J. Arthur Thomson, M.A., who 
 has acted as my assistant throughout the progress of the work. 
 Upon him much of the more laborious part of the work has fallen, 
 and without his painstaking and intelligent co-operation the present 
 translation could not possibly have been completed in the time which 
 has elapsed since it was undertaken. 
 
 WILLIAM E. HOYLE. 
 
CONTENTS. 
 
 SECTION I. 
 NATURAL HISTORY OF PARASITES IN GENERAL. 
 
 CHAPTER I. 
 NATURE AND ORGANIZATION OF PARASITES. 
 
 PAGE 
 
 Definition General scope of the Subject Pseudoparasites Degrees and 
 Varieties of Parasitism Form of the Body Organs of Fixation and 
 Locomotion Commensalism, . . . . . . 1-9 
 
 CHAPTER II. 
 OCCURRENCE OF PARASITES. 
 
 Abundance Distribution Respiration and Respiratory Organs Ectoparasites 
 
 and Entoparasites Nutrition and Mouth-Organs Encystation, . . 10-21 
 
 CHAPTER III. 
 
 THEORY OF THE ORIGIN OF PARASITES REGARDED 
 HISTORICALLY. 
 
 Theory of Spontaneous Generation Heterogeny Linne and Pallas Hypothesis 
 of Inheritance The School of Rudolphi First Proof of Metamorphosis in 
 Trematodes and Cercaria Eschricht and Steenstrup Discoveries of 
 Dujardin, von Siebold, and van Beneden Introduction of Helminthological 
 E xperiment by Kuchenmeister Its further development, . . 22-41 
 
 CHAPTER IV. 
 LIFE -HISTORY OF PARASITES. 
 
 Sexual Maturity Eggs and Embryos Developmental Stage of Eggs when laid 
 Migration of the Eggs Worm-Nests Continuous development and 
 Reproduction (Rhabditis) Haematozoa Development of the Eggs 
 externally Influence of Moisture Constitution of the Egg-Shell 
 Influence of Temperature Duration of development, . . . 42-57 
 
 Migration of the Young Brood Eggs with contained Embryos Escape of the 
 Embryos after digestion of the Shell Escape from the Host Free Embryos 
 
Xll CONTENTS. 
 
 PAGB 
 
 or Larvae Entrance of Free-living Larvae (Active Migration) Passive 
 Migration (with Food) Viability of the Germs, . . . .57-66 
 
 Development of the Germs after Migration Direct development Wandering 
 within the Body of the Host Development of the Larval or intermediate 
 stage ("Helminths of the Second Developmental Stage") Sexually 
 mature Larvae, . . . . ... 66-70 
 
 Change of Host Development and Migration of the Distomes Wandering of 
 Strongylua Of Bladder- Worms Action of the Digestive Juices Migration 
 of Penta&tomum Parasites with Free Sexual Forms Intermediate and 
 Definitive Hosts Law of numerous Embryos, and its significance in 
 regard to Parasitism Theory of erratic Embryos and of Degeneration 
 Conditions of development Duration of Life Death, . . . 71-88 
 
 CHAPTER V. 
 THE ORIGIN OF PARASITES, 
 
 AND THE GRADUAL DEVELOPMENT OF PARASITIC LIFE. 
 
 Various kinds of Parasitism Relations to Free-living Animals Free-living 
 Nomatodes Rkabdoncma nigrovenosum Parasitic Nematodes with 
 Rhabditiform Larvae Loss of the Rhabditic Stage Cestodes and 
 Trematodes Relations to the Hirudinea and Turbellaria Acanthocephali 
 and Nematodes Origin of the intermediate Host Of the intermediate 
 stage, . . .' ... : . . . 89-119 
 
 CHAPTER VI. 
 THE EFFECTS OF PARASITES ON THEIR HOSTS, 
 
 PARASITIC DISEASES. 
 
 History of the Subject Nature of Parasitic Diseases Loss of Nutritive 
 Material Consequences of growth and of increase in numbers Influence of 
 Wandering and Migration Diagnosis of Helminthiasis Therapeutics and 
 Prophylaxis Etiology Statistics of Human Parasites Sources of Human 
 Parasites Their occurrence and distribution, .... 120-170 
 
 SECTION II. 
 
 SYSTEMATIC ACCOUNT OF THE PARASITES 
 INFESTING MAN. 
 
 INTRODUCTION. 
 
 Number of Human Parasites Larval and Adult Parasites Entozoa and Epi- 
 
 zoa Zoological position, ..... 173-174 
 
CONTENTS. Xlll 
 
 PAGK 
 
 SUB-KINGDOM I. PROTOZOA. 
 
 Characters and Classification Unicellular Organisms Protophyta Parasites 
 
 resembling normal Cells, ....... 175-182 
 
 CLASS I. RHIZOPODA. 
 
 Organization Modes of Reproduction Foraminifera Radiolaria History of 
 
 Parasitic Forms, . . '. . . . .' . 182-185 
 
 Amoeba, Ehrenberg, . . . -. : . . . . . 185 
 
 Amoeba coli, Losch, . . ..-.., . - , . . . :< 186 
 
 Organization and Vital Phenomena Mode of Infection Pathological 
 
 results Experimental investigation, . -, ... . 186-191 
 
 CLASS II. SPOROZOA. 
 
 Organization and Occurrence Gregarines Pseudonavicellse Psorosperms 
 
 Coccidia Miescher's Tubes, . . . .-. '' . . 191-202 
 
 Coccidmm, Leuckart, ... . . . . 202 
 
 Coccidium oviforme, Leuckart, ...... 203 
 
 Organization Development Coccidia and Psorosperms Pathological sig- 
 nificance, ........ 203-228 
 
 CLASS III. INFUSORIA. 
 Organization Life-History Modes of Reproduction Nucleus and Nucleolus 
 
 Classification, . . . . . . . . 228-237 
 
 Order I. FLAGELLATA. 
 Definition Vital Phenomena Distribution Reproduction, . . . 237-240 
 
 Cercomonas, Dujardin, . . . . . . 240 
 
 Cercomonas intestinalis, Lambl, . . ... ., 242 
 
 Occurrence Organization Pathological significance, . . . 242-246 
 
 Trichomonas, Donne, ........ 246 
 
 Trichomonas vaginalis, Donne, . . . . .' 248 
 
 Trichomonas intestinalis, Leuckart, . . . . . 250 
 
 Order II. CILIATA. 
 Definition Organization, , . .. . . 252-254 
 
 Family BUKSARIE^E. 
 Balantidium, Claparede and Lachmann, , ; 254 
 
xiv CONTENTS. 
 
 PAGE 
 
 Balantidium coli (Malmsten), Stein, ..... 254 
 
 Definition History Occurrence Structure and Mode of Life Repro- 
 
 duction Infection, ....... 254-264 
 
 SUB-KINGDOM II. VERMES. 
 Definition History Subdivisions, ...... 265-268 
 
 CLASS I. PLATODES. 
 Definition and general characters, ...... 269-270 
 
 Order I. CESTODA. 
 Definition Polyzootic nature Head and Segments, .... 270-279 
 
 The Anatomy of Cestodes Calcareous Corpuscles Cuticle and its Appendages 
 Musculature Nervous System Excretory System Generative Organs 
 Their general Structure Male' Organs Female Organs Constitution 
 of the Primitive Eggs Structure and Development of the Embryo, . 279-330 
 
 The Development of Cestodes Historical Migrations of the Embryos 
 Structure and Development of the Bladder- Worms Cysticercoid Larva of 
 the Taeniadae Of the remaining Cestodes Development of the Dibothria 
 Modification into the definitive state General survey, . . . 330-387 
 
 SYSTEMATIC ACCOUNT OF THE CESTODES. 
 
 Classification Synopsis of Human Tape- Worms, . . . . 388-390 
 
 Family L 
 Definitions General Structure Fixing Apparatus Malformations Sub- 
 
 divisions, . . . . . . . . 391-400 
 
 Division L CYSTIC TAPE- WORMS (Cystici). 
 Definition General Characteristics Rostellum Specific distinctness of the 
 
 various forms, ........ 400-403 
 
 Subgenus Cystotaenia, Leuckart, . . . ' . . . 404 
 
 Characters Number and Distribution of the Species, . . . 404-406 
 
 Tsenia saginata, Goze, . . . . . . . 406 
 
 Definition Tape-Worms known to the Ancients Rectification of Nomen- 
 
 clature, . ' . . . . . . 406-422 
 
 Growth and Structure of the Tape-WormFormation of the Head- 
 Reproductive Organs Development of Reproductive Organs Unripe 
 and Mature Uterine Eggs Malformations Defective and Super- 
 numerary Joints Prismatic Tape- Worms Perforated Worms, . 423-458 
 
 Development and Structure of the Bladder- Worm Experimental Rearing 
 
 Acute Cestode Tuberculosis, ...... 458-475 
 
 Distribution and Frequency Modes of Infection Duration of Life 
 
 Medicinal significance, . . . . . .476-488 
 
CONTENTS. XV 
 
 PACK 
 
 Teenia solium, Rudolphi, ....... 488 
 
 Definition General Characters, ...... 488-490 
 
 Origin and Development from the Bladder-Worm of the Pig Breeding 
 Experiments Breeding of the Bladder- Worms Of the Tape-Worm 
 Occurrence of Cysticercus cdlulosce, ..... 490-498 
 
 Development and growth of Teenia solium Development of the Bladder- 
 Worm Structure of the full-grown Bladder- Worm Duration of Life 
 Identity with the Bladder- Worm of Man Development and Growth 
 of the Tape-Worm Malformations, . . < . 498-518 
 
 Organization of Teenia solium Ripe Proglottides Head and circlet of 
 
 Hooks Development of the Generative Organs Ripe Eggs, . 519-528 
 
 Occurrence and Medical significance The Adult Tape-Worm Trans- 
 ference of the Bladder- Worm Modes of Infection Medical signifi- 
 cance of the Tape-Worm Of the Bladder-Worm Historical Account 
 Cysticercoid Disease of Swine Of Man Mode of Infection Self- 
 infection Occurrence in different Organs, in the Muscles, in the 
 Eye, in the Brain Cysticercus racemosus, Cysticercus turbinatus 
 Oldest record of Bladder-Worms in Man Symptomatology of the 
 Disease, . . . . . . . . 521-561 
 
 Taenia acanthotrias, Weinland, ...... 561 
 
 Definition and History, . . . . . . . 561-563 
 
 Teenia marginata, Batsch, ...... 563 
 
 Definition Doubtful occurrence of the Bladder- Worm in Man Distinctions 
 between this and related species Development of the Bladder- Worm 
 (Cysticercus tenuicolUs) Experimental Breeding and Pathological 
 significance Full-grown Bladder- Worm, .... 563-578 
 
 Subgenus Echinococcifer, Weinland, . . . . .. 578 
 
 Peculiarity of the Cysticercoid Stage Specific distinctness Metamor- 
 phosis of the Hooks Historical Account of the Echinococcus 
 Acephalocysts, . . . . . . . 578-586 
 
 Tsenia echinococcus, von Siebold, ..... 586 
 
 Definition Description of the Adult Worm Generative Organs Duration 
 
 of development Supposed occurrence in Man, ... . 586-594 
 
 Development of the Echinococcus-TSladder Experimental Breeding 
 
 Structure of the Cuticle Absence of Vascular System, . . 594-603 
 
 Structure and Development of the Echinococcus-He&ds Brood-Capsules 
 
 Budding of the Heads, * . . . . . 603-611 
 
 The Formation of Daughter-Bladders Echinococcus simplex or granosus 
 Interlamellar Budding Echinococcus hydatidosus Metamorphosis of 
 Heads into Bladders Metamorphosis of Brood-Capsules into Bladders 
 Direct formation of Daughter-Bladders Echinococcus multi- 
 locularis Chemical Constitution of the Bladder- Wall and Fluid, . 611-631 
 
XVI CONTENTS. 
 
 FACE 
 
 Occurrence and Medical Significance Multiple Echinococci Etiology 
 Distribution and Frequency of the Disease Echinococcus in the 
 Icelanders and Pastoral Peoples Influence of Age and Sex Growth 
 of the Parasite Prognosis Nature and Symptoms of the Disease 
 Death of the Eckinococcus, .... . 632-652 
 
 Division II. ORDINARY TAPE- WORMS (Cystoidei). 
 General Characters Larval Stages Number of Species, . . . 652-656 
 
 Subgenus Hymenolepis, Weinland, . . . .' . 657 
 
 Taenia nana, von Siebold, . . . .657 
 
 Definition Development Eggs, . . - 657-661 
 
 Taenia flavo-punctata, Weinland, . - 881 
 
 Definition and Characters, . . . 661-663 
 
 Taenia madagascariensis, Davaine, . . . . . 663 
 
 Definition and History, . . . 663-665 
 
 Subgenus Dipylidium, Leuckart, . ... . . . 665 
 
 Taenia cucumerina, Rudolphi, . . 665 
 
 Definition Historical Account Development Melmkoifs Discovery 
 
 Egg- Masses, . . 665-673 
 
 Family II. BOTHRIOCEPHALID^. 
 Definition General Characters Head, Nerves, and Excretory Organs Generative 
 
 Organs Number of Species, ...... 674-682 
 
 Bothriocephalus, Rudolphi, . . . . 682 
 
 Bothriocephalus latus, Bremser, . . 683 
 
 Definition Historical Sketch Anatomy Muscles Vessels Generative 
 Organs Male Organs Female Organs Their Development Abnor- 
 malities, ...... v 683-714 
 
 Occurrence Historical Sketch Braun's Discovery Early Stages of 
 
 Development Ciliated Embryos Metamorphosis, . . .714-729 
 
 Distribution and Medical Significance Modes of Infection Specific and 
 
 Individual Differences, . . . . . 729-735 
 
 Bothriocephalus cristatus, Davaine, ..... 735 
 
 Bothriocephalus cordatus, Leuckart, . . 736 
 
 Definition Occurrence in Man Description and Specific Distinctness 
 
 Peculiarities of Young Forms, . . . . . 736-745 
 
 Bothriocephalus liguloides, Leuckart, . . . 745 
 
 Definition Historical Account Occurrence in Man Anatomy 
 
 Disposition of the Organs Structure of the Head, . . . 745-751 
 
LIST OF ILLUSTRATIONS. 
 
 Acanthobothrium coronatum, larval state of, after van Beneden, . 218 374 
 Amoeba coli in intestinal mucus, with blood-corpuscles, Schizomycetes, 
 
 and similar bodies (after Lusch), . . . , 94 186 
 A nthomyia canicularis 
 
 Larva of, , 88 143 
 
 Larva of, from the intestine of man, . . . . 7 15 
 
 ArchigctesSieboldi(x 60), ...... 47 69 
 
 ...... .73 116 
 
 ...... 220 376 
 
 . . . . . . ' . 353 676 
 
 ....... 356 681 
 
 Ascaris lumbricoides, Eggs from, 32 53 
 
 Aspidogastcr conchicola (after Aubert), .... 48 69 
 
 74 115 
 Balantidium coli 
 
 In conjugation (after Wising), . . . . .129 260 
 
 In various stages of division, . . . . .130 261 
 
 With widely opened peristome (dorsal view), . . . 127 255 
 Bladder- worm 
 
 From the brain, with a spirally coiled body ( x 12), , . 301 556 
 
 From the pig, after the digestion of the bladder ( x 20), . 287 513 
 
 Head after digestion of the caudal bladder, . . . 54 75 
 
 Head of, from the pike, ...... 390 727 
 
 In the anterior chamber of the eye, after de Wecker ( x 3), . 299 553 
 
 Longitudinal section through the head process ( x 40), . . 286 506 
 
 Of the pig, with evaginated head ( x 2), . . . 23 36 
 
 ... 285 506 
 
 With invaginated head ( x |) . . >. . 23 36 
 
 . . 284 506 
 Sagittal longitudinal section through the protruded head of, from 
 
 the pike, ....... 392 128 
 
 The head and receptacle of, from a muscle about 6 mm. in size ( x 25), 281 503 
 
 Transformation of, into a tape- worm (Tcenia serrata), ... 26 37 
 
 With extruded head, . . . . . 53 75 
 
 Young, from the pike, with invaginated head, . . . 389 727 
 
 390 727 
 Bladder- worm of the rabbit 
 
 Cephalic end of a young ( x 45), . ' , . . .189 347 
 
 Longitudinal section through the head of ( x 60), . . . 193 350 
 
 Metamorphosis of, into the young tape-worm ( x 4), . . 224 382 
 Transverse section of the anterior end of, at the level of the 
 
 suckers ( x 40), . . . . . .192 503 
 
 Bodo saltans (after Stein), . . . . . .118 237 
 
 b 
 
XV111 LIST OF ILLUSTRATIONS. 
 
 FIG. PAGB 
 
 Bothriocephalu s 
 
 Diagrammatic representation of the course and connections of the 
 
 vagina, as seen in longitudinal section, . . . 371 709 
 Egg of, with imperfectly developed embryo, being expelled by 
 
 compression, . . . . v , . .384 722 
 
 Eggs of, with operculum, ..... 38 59 
 
 Encapsuled larva of a, from the smelt, . . . .. 375 715 
 
 Head of a, reared in the cat from bladder-worms from the pike 
 
 (after Braun), ...... 380 719 
 
 Larva of, from the skink ( x 20), . . .352 674 
 
 Larva of, from the smelt, . . . . .221 377 
 
 Segment of, with yolk chambers and "yellow ducts" (after Eschricht), 370 708 
 
 Transverse section through the body of a larva of, . , 391 728 
 
 Young, from the alimentary canal of the dog, . . . . 376 716 
 
 Young, from the intestine of the cat, after feeding with bladder- 
 worms from the pike, ..... 379 719 
 
 Bothriocephalus cordatus 
 
 A number of mature joints of, . . . . . 395 737 
 
 From man, . , . . . "" . . 350 674 
 
 397 739 
 
 Head of, from the side and from above ( x 8). . . . 398 739 
 
 Four young specimens of, . . . . .401 743 
 
 Head and anterior portion of ( x 5), . . . . 140 278 
 
 . 394 737 
 
 Three joints of, seen from the dorsal and from the ventral surface ( x 2), 399 739 
 
 Transverse sections of the head of ( x 20), . . . 400 742 
 
 Uterus of, ... .396 737 
 
 Bothriocephalus latus ....... 137 275 
 
 357 684 
 
 ,, ,, (cephalic end) ( x 8), . . . 226 389 
 
 Ciliated embryo of ( x 500), 177 327 
 
 Club-shaped head of, . . 393 734 
 
 Development of the reproductive organs in, . . . 372 712 
 Diagrammatic representation of the course and connections of the 
 
 vagina, as seen in longitudinal sections, . . . 367 701 
 
 Egg of, with embryo, ...... 36 57 
 
 Egg, showing yolk-cells and shell ( x 300), . 171 321 
 
 Eggs of (x 300), .... .359 685 
 
 Embryo of, escaping from its ciliated envelope, . . 388 725 
 
 Embryo of, in the egg, ... .385 723 
 
 Female generative organs of, from the ventral surface ( x 20), . 366 700 
 
 369 705 
 Female sexual organs of, showing the uterus, ovary, shell-gland, 
 
 and yolk -gland ( x 12), . . . .157 305 
 
 Free ciliated embryos of ( x 500), . 386 723 
 
 Free embryo of , ... 40 60 
 
 Free-swimming embryo of, 70 110 
 
 (x 500), . . . .351 674 
 
 (x 600), . . . .374 715 
 
 Free-swimming embryo of, with the protoplasmic threads, &c. 387 725 
 
 Generative organs of (ventral aspect), . . . 141 278 
 
 Head of (x 8), ... . 358 684 
 
 Larva of (x 55), . 354 676 
 
 Larva of, with protruded head, . 378 718 
 
 Larvae of, from the pike, . . 360 686 
 
 377 717 
 
LIST OF ILLUSTRATIONS. XIX 
 
 Longitudinal diagrammatic representation of the three generative 
 
 ducts, . 363 694 
 
 Male and female sexual organs of(x20), . . . 170 318 
 
 Male generative organs of, seen from the dorsal surface ( x 20), 365 698 
 
 Mature joint of ( x 8), . . . . . .362 693 
 
 Ovum of, with yolk-cells and shell, . . . . 381 721 
 
 Ovum of, after Schauinsland, with fotir embryonic cells and en- 
 veloping cells on the granular yolk ( x 600), . . 382 722 
 Another ovum, with covering cells apposed to the embryonic 
 
 body (x 600), .... . . . .282 722 
 
 Ripe joint of, with the uterine rosette ( x 6), . . 368 702 
 
 Series of joints with double genital apertures, . . . 373 713 
 
 Sexual organs of, from the ventral side ( x 20), . . . 159 306 
 Transverse section through the body of, at the level of the 
 
 cirrhus-pouch ( x 10), ..... 364 695 
 
 Transverse section through the head of a young ( x 55), . 355 678 
 
 Transverse sections through the body of ( x 10) . . . 361 689 
 
 Bothriocephalus liguloides . . .'. . . . 402 746 
 
 Head of ( x 5), . . . . . .404 751 
 
 Transverse section through the larval body of, . . . 403 749 
 
 Bothriocephalus proboscideus, Excretory apparatus of, after Steudener 
 
 (x 32), 155 301 
 
 Bothriocephalus salmonis, Embryonic development of, after Kolliker 
 
 ( x 300), . 178 328 
 
 Brain of a lamb with tracks of Ccenurus, . . . . 81 135 
 
 ..... 206 359 
 
 Brood-capsule 
 
 Closed and ruptured, showing their connection with the paren- 
 
 chymal layer ( x 40), ..... 325 606 
 
 Development of, and of the appended heads ( x 90), . . 328 610 
 
 Metamorphosis of the, into bladders, after Naunyn ( x 90), . 332 621 
 
 With heads of Echinococcus in the interior ( x 40), . . 324 605 
 
 Cercaria 
 
 A free, ........ 50 72 
 
 A free and an encapsuled, the latter without tail, . 21 and 22 34 
 
 An encysted, without tail, . . . . .51 73 
 
 Cercomonas from the liver (after Lambl), . . . . 122 244 
 
 Cercomonas intestinalis (after Davaine), . . . .121 242 
 
 Cercomonas muscce at different stages (after Stein), . . . 117 237 
 
 Coccidia 
 
 Development of psorosperms in, . . . . . Ill 213 
 
 Enclosing psorosperms, . . . . . .112 214 
 
 From the human liver, . . . . . .114 223 
 
 From the intestine of the domestic mouse, . . .100 197 
 
 . , 113 219 
 
 From the kidneys of the garden snail, . . . * 101 198 
 
 From the liver, . . . . . . ; 110 210 
 
 Coccldium-nodule, Cross section of a, slightly enlarged, . . 108 208 
 
 Coccidium oviforme 
 
 From the liver of the rabbit, . . . . .102 198 
 
 (x 550), . . . . . . 106 204 
 
 Ccenurus 
 
 Head and body of, in situ ( x 100), '. . . .197 352 
 
 Heads of ( x 25), . - . . .203 356 
 
 Passages of, in the brain of a lamb, .... 181 340 
 
XX LIST OF ILLUSTRATIONS. 
 
 FIG. PAGE 
 
 Cucuttanus, Embryo of, . . . . . . .65 102 
 
 Cysticercus 
 
 Head rudiment of an adult ( x 12), . . . . 268 465 
 
 Subretinal, in the eye (after de Wecker), . ; . 298 552 
 
 With evaginated head ( x 3), . ., . 269 465 
 
 Cysticercus acanthotrias 
 
 Head and circlet of hooks seen from above, after Weinland ( x 60), 302 562 
 
 Hooks of, after Weinland ( x 280), .... . . 303 562 
 
 Cysticcrcus arionis 
 
 With head retracted and protruded ( x 50), . . . 209 362 
 
 . v . * 336 652 
 
 Cysticcrcus ccttulosce 
 
 Completion of the head formation in (x 15), . . . 283 505 
 
 Head of, with rudiment of the receptacle ( x 25), . . . 279 502 
 
 Metamorphosis of the head-process into the head proper ( x 20), 282 505 
 The beginning of the bending of the head inside its receptacle 
 
 (x 25) 280 503 
 
 Various stages in the formation of the head of ( x 45), . . 188 346 
 
 With the formation of the head just beginning ( x 10), . 278 501 
 
 With the head in the receptacle ( x 2), . .235 404 
 
 Cysticercus fasciolaris, . . ; . . . .202 355 
 
 * . . .236 405 
 
 Cysticcrcus glomcridits 
 
 (After Villot) ( x 50), . . . .. . . _ 210 363 
 
 ( x 200), . . . . . .214 368 
 
 ( x 50), . ... . . .337 652 
 
 Cysliccrcus pisiformis 
 
 A piece of liver from the rabbit, showing passages made by, . 46 69 
 Before the development of the head, with granular sheath and 
 
 cyst(x 60), . . :->. . . 183 341 
 
 Head and body of, in completely evaginated state ( x 19), . 199 352 
 
 Head of, with vascular system ( x 45), . . .190 349 
 
 Head of, just mature ( x 40), ..... 191 349 
 
 Metamorphosis of the head of ( x 45), . . . 194-196 351 
 
 Piece of rabbit's liver with passages of ( x 10), . . . 82 136 
 
 ... 207 360 
 
 With head half evaginated ( x 6), . . .198 352 
 
 Young . 12 19 
 
 Cysticercus raccmosus 
 
 (After Marchand), 300 554 
 
 (After von Siebold), ... ... 59 84 
 
 Cysticercus Tcenice saginatce 
 
 Embedded in the muscle, . . . . .267 465 
 
 Evaginated head of ( x 30), , . ... . 270 466 
 
 Head of, with frontal sucker and vascular ring ( x 30), . . 248 437 
 Head-rudiment of, before and after the development of the suckers 
 
 (x 25), . ... . . . 265-66 463 
 
 Longitudinal section through the head in situ ( x 30), . . 271 466 
 
 Cysticcrcus tenebrionis, Development of, after Stein ( x about 100), . 208 360 
 
 Cysticcrcus tenuicollis 
 
 (After Bremser), ...... 305 564 
 
 Anterior end of, with retracted neck and ribbon-like appendage, 313 577 
 
 Exit of a young, from the liver, . . . . . 83 136 
 
 Longitudinal section through the head of an adult ( x 20), . 312 576 
 
LIST OF ILLUSTEATIONS. XXI 
 
 FIG. PAGE 
 
 The head process ( x 15), ..... 310 573 
 
 Three months old, ...... 311 575 
 
 Young, ........ 310 573 
 
 Young, in situ, . . . . . .309 572 
 
 Development of an Echinococcus -like cysticercoid from the body-cavity 
 
 of the earth-worm, after Mecznikoff ( x 25), . . .213 366 
 
 Distomum hcematobium, male and female, . . . " . 29 45 
 Distomum hcpaticum 
 
 (Natural size), . . . ... .. 68 104 
 
 Ciliated embryo of, with an eye speck, . . * . 69 108 
 
 Egg of, with embryo, . . . . .. 35 57 
 
 Free embryo of, . . . . . 39 60 
 
 Distomum luteum (young), with suckers and viscera (after de la Valette), 1 6 
 
 Dochmius duodenalis, Cephalic extremity of ; profile and front view, . 10 18 
 Dochmius trigonoccphalus 
 
 A, Free living young form ; B, Young parasite, . . 63 99 
 
 Rhabditis-like condition of young stage of, . . . 43 62 
 Echeneibothrium minimum 
 
 (After van Beneden) ( x 8), . . . .226 389 
 
 Chain of joints of, . . -. . . .134 273 
 
 ,, ,, isolated living head and tape- worm, . 24 and 25 37 
 Isolated living head of, from the intestine of Tryyon pas- 
 
 tinaca, ..... . 133 273 
 
 Strobila and proglottis of (after van Beneden), . . 135 and 136 274 
 
 Echinococcus, . . . . . . . .13 19 
 
 Before the beginning of the segmentation ( x 15), . . 319 591 
 
 Bladder, eight weeks old ( x 20), . . . .321 597 
 
 Brood-capsule of, with adherent heads in various stages of de- 
 velopment ( x 36), ...... 204 357 
 
 Brood-capsule of, with retracted head and with two appended 
 
 buds at different stages ( x 100), .... 314 579 
 
 Diagrammatic representation of a proliferating, . . . 205 357 
 Head, metamorphosis of an, into a bladder in the interior of the 
 
 brood-capsule, after Naunyn ( x 60), . . .331 620 
 
 Head, with the anterior part of the head invaginated ( x 90), . 323 604 
 Heads, development of the, from those hanging freely into the 
 
 internal cavity of the brood-capsule, after Wagener ( x 90), 327 608 
 
 Hooks (x 600), 315 581 
 
 In its natural size and position, . . . . . 329 613 
 
 Proliferation of the membrane of an, . . . . 330 614 
 
 Young, four weeks old, escaping from the capsule ( x 50), . 320 594 
 
 Echinococcus multilocularis ( x 30), ..... 335 629 
 
 Section through an, . . . . . - 333 624 
 
 Echinococcus racemosus, . . . . . .334 628 
 
 Echinococcus veterinorum . .... 317 587 
 
 Brood -capsule of, with adult and hollow rudimentary heads 
 
 ( x 40) ,326 608 
 
 Head of ( x 90), ......... 322 603 
 
 Echinorhynchus angustatus, male, . . . . . 11 18 
 
 Embryos of ; (^4) the profile; (B) ventral view,. . . 72 112 
 
 Echinorhynchus gigas, Egg of, with embryo, .... 37 57 
 
 Echinorhynchus spirula, natural size (after Westrumb), . . 71 110 
 
 Eggs of worms found in the alimentary canal of man, . . . 90 146 
 
 Entozoa in the second stage of development, , .. ... 45 68 
 
XX11 LIST OF ILLUSTRATIONS. 
 
 Filaria sanguinis Jwminis (after Lewis), .... 31 50 
 
 Flea, Larva of the, . . . . . . .41 60 
 
 Flesh of pig with bladder- worms (natural size), . .. t . 91 155 
 
 Flesh of pig with Trichina; ( x 45), . . ' . . . 92 155 
 Gregarines, encapsuled ; (.4 ) after conjugation ; (B) after formation of 
 
 pseudonavicellae, . . . . . . . . 96 192 
 
 (A) Monocystis agilis ; (B) Greyarina cuncata (C) Stylorhynchus 
 
 oligacanthus, . . . . . 95 192 
 
 ffexamita intcstinalis, in the young and adult states (after Stein), . 120 240 
 Hirudo medicinalis, Cephalic end of, with the three mandibles at the 
 
 base of the oral cup, . . , ... 9 17 
 Infusorians with undulating longitudinal membrane from the intestine 
 
 of the hen (after Eberth), . . . . .124 248 
 
 Lacerta vivipara, Unarmed cystic worm from the body-cavity of ( x 30), 185 343 
 
 Liver of a rabbit with Coccidium-nodnles, . . . .107 204 
 
 Measly pork, .-57 83 
 
 " , 277 494 
 
 Miescher's tubes, Extremity of one of, with its contents, . . 105 201 
 
 Monostomum capitellatum . . . . . . .16 30 
 
 ,, ,, Ciliated embryo of, . . . .69 108 
 
 Monostomum mutabile, Infusorian-like embryos of, with the " necessary 
 
 parasite," . .... 17 31 
 
 Musca vomitoria, Larvae of, . . . . . 8 15 
 
 (Natural size and enlarged), . . . . 89 144 
 
 Muscle -Trie h I/UP, seven weeks old, in the distended sarcolemma-sheaths, 77 129 
 
 Nasua socialis, Kidney of, with Eustrongylus in the distended pelvis, . 76 129 
 
 Oxyuris ambigua (young), . . . . . 64 101 
 
 Oxyuris vermicularit, Eggs of, . . . . . . 34 56 
 
 Paramcecium coli (after Malmsten), . -. . . . 128 255 
 
 Pediculus (Pktkirius) pubis, . . . . . ... 2 7 
 
 Pentastomida, Lung of rabbit infected with, .... 55 78 
 
 Pcntastomum, Lung of a rabbit infected with, . . . .84 137 
 
 Pentastomum constrictum (after Aitken), . . . .85 137 
 
 Pcntastomum denticulatum, . . . . . .27 41 
 
 ., 56 78 
 
 From the liver of man, . . . . . . 5 14 
 
 Piece of a rabbit's liver with bladder- worm passages ( x 10), . . 182 341 
 Piestocystis variabilis, Longitudinal section of an unarmed cystic worm 
 
 from the lung of a crow ( x 30), ... . .184 343 
 
 Pseudonavicellae, with germinal rods in their interior, . . .97 194 
 
 Psorospenn-balls and Gregarines on human hair, Lindemann's, . 116 227 
 
 Psorosperm-nodule, The epithelium of a, filled with parasites, . 109 209 
 
 Psorosperm-saccule from the urinary bladder of the pike (after Lieberkiihn), 98 196 
 Psorospermiae from the connective tissue of the human kidney (after 
 
 Lindemann), . .. . . . . .115 226 
 
 Psorosperms, (A), from the urinary bladder of Gadus lota; (B), from 
 
 the gills of the bream, ., . . . . . 99 197 
 
 Pulex penetrans, male and female, . ... .28 44 
 Rainey's bodies, one of, within an isolated muscular fibre, enlarged 100 
 
 diameters, 104 200 
 
 Rainey's tubes enlarged about 40 diameters, * 103 200 
 
 Redise, Bojanus' " kingsyellow worms," from the pond-snail, 18 31 
 
 With brood of Distomes in the interior, . . . 75 118 
 
 (A ) with germs ; (B) with Cercarise in the interior ; (C) free Cercariae, 19 31 
 
LIST OF ILLUSTRATIONS. XX111 
 
 FIG. PAGE 
 
 RJiabditis terricola, ....... 30 48 
 
 Adult female and young, . . . . .60 95 
 
 Embryo of, ...... 42 62 
 
 Rhabdonema (Ascaris) nigrovenosum, Khabditoid form of, 61 97 
 
 Rhabdonema nigrovenosum, Mature embryo of, . . . .62 97 
 
 Sarcoptcs scabiei, * ... . ,. . . . 6 14 
 
 ,,... 86 140 
 
 Scabies norvegica, Crust of, with mites, their borings, eggs, and excreta, 87 140 
 
 Sclerostomum tetracanthum, encysted, . . . .14 20 
 
 Scolcccs ( x about 30), . . . ... 217 372 
 
 Spiroptera murina, Young form of, from the meal-worm, . + 45 68 
 
 Sporocyst and Redia, with Cercarise in the interior, . ... 49 71 
 
 StrongylusJHaria,F^mbryoof, . . . . . . 65 102 
 
 Tcenia, Double joint of. with three sexual openings, . . . 258 451 
 
 Embryo of ( x 100) . 80 132 
 
 .... .179 330 
 
 Tcenia ccenurus ( x 10-15), . ... . . . . .'308 568 
 
 Cephalic end of, with hexamerous symmetry ( x 25), . . 232 396 
 Connection between the different parts of the female generative 
 
 apparatus in, . . . . . .163 314 
 
 Form of uterus in, ... . . . .308 568 
 
 Joint of, with excretory vessels and generative organs ( x 10), . 154 299 
 
 Larger and smaller hooks of ( x 280), . . . .307 567 
 
 Sexual organs of ( x 10), ..... 158 306 
 
 165 314 
 Tcenia crateriformis, Embryonal hooklet of, from a bird, after v. Siebold 
 
 (x 700), 174 322 
 
 Tcenia cucumerina, ....... 347 666 
 
 Cysticercoid of ( x 60), ...... 211 364 
 
 ....... 338 653 
 
 348 669 
 
 Cysticercus of, from the dog-louse, .... 45 68 
 
 Head of, with rostellum and hooks in different stages of 
 
 contraction ( x 140), ..... 346 665 
 
 Proglottides of, in a sexually mature state ( x 20), . . 349 672 
 
 Rostellum of ( x 140), 229 393 
 
 Tcenia echinococcus ( x 10), . . . . . .226 389 
 
 Adult specimen of ( x 12), . . . . .138 277 
 
 . . . 316 587 
 
 Generative organs of ( x 80), . . . . . 318 590 
 
 Sexual organs of ( x 100), 164 314 
 
 Tcenia elliptica, Recently formed egg of ( x 600), . .172 321 
 
 Sexually mature proglottis of, . . . . 143 279 
 
 Tcenia flavo-pimctata, after Weinland ..... 344 661 
 
 Ripe proglottides of, one barren ( x 40), . . . 345 662 
 
 Tcenia marginata, Embryonic development of ( x 550), . . 176 326 
 
 Form of uterus in ( x 6), . . . . < . 308 568 
 
 Hooks of ( x 280), 304 564 
 
 Recently formed egg of ( x 600), . . .172 321 
 
 Tcenia mediocanellata (natural size), . . . . .67 104 
 
 Tcenia nana ( x 18), . . . . . 340 657 
 Head of, with retracted rostellum ( x 100) ; (A) an isolated hook 
 
 ( x 600), . . ... . . .341 658 
 
XXIV LIST OF ILLUSTRATIONS. 
 
 1 
 
 FIO. PAGE 
 
 Occurring in man, egg of ( x 400), . . . .175 322 
 
 Proglottides of ( x 100), . . . . . .342 659 
 
 Proglottides of, at maturity (x 100), . . . .167 316 
 
 Ripe egg of, with embryo ( x 250), . . . . 343 660 
 
 Tcenia nymphcea, Embryo of ( x 400), . * . . - . 173 321 
 
 Tcenia perfoliata, Male and female organs of, after Kahane (x 15), . 166 315 
 
 Mature joint of, with uterus ( x 10), .... 168 316 
 
 Nervous system of ( x 20), . . . . . 152 296 
 
 Sexual organs of, from the horse, after Kahane ( x 15), . ' 162 313 
 
 Tcenia sayinata, ........ 237 407 
 
 Cephalic end of, in retracted and extended state ( x 8), . . 246 433 
 
 Cross section of a joint of ( x 38), . . . 148 292 
 
 Development of the efferent generative organs in, . 252 446 
 
 Development of the germ-producing organs ( x 5), . . 253 447 
 
 Eggs of, after E. van Beneden ( x 550), . . . .256 449 
 
 Formation of the first lateral branches of the uterus ( x 5), . 255 448 
 
 Four last joints of, about to be liberated, . . . 150 294 
 
 Generative organs of ( x 10), ..... 249-50 439-43 
 
 Half -ripe joint of ( x 2), . . . . . .296 528 
 
 Head of, in a state of contraction (x8), . . . 244 431 
 
 Head of, in longitudinal section ( x 25), . . . . 247 435 
 
 Head of, in contracted and extended condition ( x 8), . . 238 408 
 
 Isolated proglottides of, . . . . . .132 271 
 
 240 423 
 
 Joint of, . . . * . . . .169 316 
 
 Joint of, with unusually simple structure of the uterus ( x 2), . 243 427 
 
 Joints of, with two and three genital openings, . . . 257 450 
 
 Longitudinal section of (young chain of joints) ( x 25), . . 147 291 
 
 149 IN 
 
 Longitudinal section through (a young chain) ( x 25), . . 245 431 
 Lower end of the vagina, showing its connection with the uterus 
 
 ( x 30), . - . . - , . .254 447 
 Mehlis' body in connection with the various parts of the female 
 
 productive organs ( x 30), . . . . 251 444 
 
 Prismatic proglottides, . . . . . 260 453 
 
 With double porus genitalis, ..... 262 456 
 
 In transverse section through the porus genitalis ( x 8), . 261 455 
 
 Proglottides of, in various conditions of contraction, . . 44 65 
 
 Proglottides of, in motion, . . . . .241 425 
 
 Ripe segment of ( x 2), . . . . . .239 408 
 
 Series of joints with perforated proglottides, . . . 263 457 
 
 Supernumerary joint of (x ), . . . 233 399 
 
 Supernumerary joints of, . . . . . . 259 452 
 
 Tape-worm form of, ...... 131 271 
 
 Var. abietina, Ripe segment of, after Weinland ( x 2), . . 272 479 
 
 Young bladder- worms of ( x 30), . . . .186 345 
 
 Young bladder-worms of, with rudimentary head ( x 30), . 264 460 
 
 Tcenia serrata 
 
 Calcareous corpuscles of, . . . . . .145 
 
 Development of the hooks of, . . . .146 287 
 
 Embryonic development of ( x 550), . . . .176 326 
 
 Form of uterus in ( x 4), . . . . .308 568 
 
 Head of, with its excretory vessels ( x 24), . . _. 153 298 
 
 Larger and smaller hooks of ( x 280), . . . 306 566 
 
LIST OF ILLUSTRATIONS. XXV 
 
 FIG. PAGE 
 
 Longitudinal section of a young, consisting almost entirely of 
 
 head and neck ( x 60), ..... 151 295 
 
 228 392 
 
 234 401 
 Rudimentary heads of, at the beginning and at the end of the 
 
 protrusion of the head ( x 20), . . . 200 and 201 354 
 
 Twenty hours old, with incipient segmentation (x 10), . . 225 383 
 
 Young bladder-worms of, with rudiment of head ( x 12), . 187 345 
 
 Tcenia setic/era, Two proglottides of, from the goose, after Feuereisen, 160 311 
 
 Tcenia solium 
 
 Apex and hooks of, .-.. . -, ,. ,. . 139 278 
 
 Apical surface and circle of hooks in ( x 80), . . '. 231 395 
 
 .... 292 521 
 
 Cephalic end of, . % ... i . . 4 8 
 Cross section of, showing middle and cortical layers under low 
 
 power, . . . . ... . 144 281 
 
 Cysticercus of, from the pig, . . . . .45 68 
 
 Egg of, with shell and yolk-membrane ( x 400), . . .,- 175 322 
 
 Eggs of, with and without primitive vitelline membrane ( x 450), 297 528 
 
 Embryo containing egg (without yolk-membrane) ( x 400), . 173 321 
 
 Generative organs of, . . . . 142 278 
 
 Half -ripe and ripe joint, . . . . . . 275 489 
 
 Half -ripe joint of (x 2), ...... 295 528 
 
 Head of ( x 35), . . . . .227 391 
 
 . ' . . .274 489 
 
 . . . . . . .291 521 
 
 Head of, from the intestine of a rabbit ( x 25), . . . 223 381 
 Head of, from the intestine of a rabbit, in different stages of 
 
 motion ( x 25), .288 513 
 
 Larger (anterior) and smaller (posterior) hooks of ( x 280), . 293 523 
 
 Proglottides of, with slightly branched uterus ( x 2), . . 290 520 
 
 Reproductive organs of ( x 10), ..... 294 526 
 
 Two joints of, with branched uterus ( x 2), . . . 156 305 
 
 Two proglottides of, with uterus ( x 2), . . . . 276 489 
 
 Two segments of, with branched uterus ( x 3J), . . . 289 520 
 Tcenia torulosa 
 
 Young form of, in Cydops serrulatus, after Grtiber ( x 25), . 212 365 
 
 339 653 
 
 Tcenia uncinata, Generative organs of, after Stieda ( x 25), . . 161 312 
 
 Tcenia undutata, Rostellum of, after Nitsche ( x 100), . . 230 394 
 Tape-worm . 
 
 Egg of, from a bird, Tcenia nymphcea, . . 33 55 
 
 Eggs of, with six-hooked embryo, . . . .20 32 
 
 Piece of a mummified, . . . / . . 273 485 
 Tenebrio molitor, Encapsuled tape -worm embryo, and the resulting cystic 
 
 worm from, after Stein (x 100), . . . .180 331 
 
 Tctrarhynchus 
 
 Cysticercoid, from a Mediterranean percoid (x 20), . . 215 370 
 
 Longitudinal section of a still imperfectly developed ( x 25), . 219 375 
 
 Longitudinal section of an isolated head of ( x 10), . . 222 380 
 
 Tetrarhynchus sepice (x 12), . . . . . 216 371 
 
 (Isolated head) ( x 12), . ... . . 226 389 
 
 Thetis, Blood-corpuscles of, partly with enclosed granules of pigment, 
 
 after Hfeckel, .... 93 178 
 
XXvi LIST OF ILLUSTRATIONS. 
 
 Trichina-c&psule, with connective-tissue covering (in situ), in B, calcified, 15 21 
 Trichina spiralis A , Embryo ; B, Intermediate form ; C, Sexual form 
 
 (unimpregnated female), . ... . . 66 103 
 
 Trichinosed pork ( x 45), 83 
 
 Trichocephalus dispar, ..... 53 
 
 ,, in situ, .... 7 
 
 Trichomonas batrachorum (after Stein), ..... 119 239 
 
 123 247 
 
 Trichomonas intestinalis, after Zunker, . . . .126 250 
 
 Trichomonas vaginalis, after Kblliker, . . . . .125 249 
 
 Ureter, with excrescences due to the presence of Distomum, . 78 130 
 
 Uterus of a free proglottis ( x 2), . 242 426 
 
 Worm aneurism of the horse, . ... 52 74 
 
 79 131 
 
SECTION I. 
 
 NATURAL HISTORY 
 
 OF 
 
 PARASITES IN GENERAL. 
 
CHAPTEK I. 
 NATUBE AND OBGANIZATION OF PAEASITES. 
 
 THE term " Parasite/' in its widest sense, includes all those creatures 
 which inhabit a living organism, and obtain nourishment from its 
 body. 
 
 This definition includes not only vegetable and animal parasites 
 (phytoparasites and zooparasites), but also parasites on plants and 
 on animals. The larva that inhabits the wood of a tree or the pulp 
 of a fruit is to be regarded as a parasite in no less degree than the 
 thread-worm of the human intestine ; and the beetle that defoliates 
 our forests is quite as much a parasite as the louse upon the feathers 
 of the swallow. Parasitic life, then, as thus understood, is an ex- 
 ceedingly widespread phenomenon. 
 
 So long as the term " parasite " was confined to certain special 
 forms, as was the case formerly, it followed as a necessary con- 
 sequence that parasitism was an isolated phenomenon, and bore no 
 relation to any other mode of existence. Now, however, this view is 
 known to be false, a matter of great importance when we come to 
 study the subject from a historic point of view. It is not merely 
 the intestinal worms and allied forms that are to be included 
 among parasites, but also numerous creatures that sometimes resemble 
 so completely certain free-living animals, except in the nature of their 
 food, that an independent mode of existence has been actually as- 
 cribed to them. Does it correspond with the common view of the 
 peculiar nature of parasitism, that a creature which, according to the 
 definition just given, ought to be regarded as a parasite, should be 
 sharply distinguished from another free-living animal simply because 
 it feeds upon a living branch instead of dead wood, or on green 
 foliage instead of withered leaves ? Do not the value and meaning 
 of these differences appear less than those which obtain between car- 
 nivorous animals on the one hand and herbivorous on the other ? 
 
 The question raised here remains the same, when we limit more 
 narrowly the conception of parasitism, which on practical grounds 
 is advisable for the purpose of this work, and confine it entirely to 
 animals living as parasites upon other animals. 
 
2 NATURE AND ORGANIZATION OF PARASITES. 
 
 Under this limitation, the group of parasites appears at first sight 
 to be considerably more restricted than it did from the former 
 wider point of view, and in earlier days, when it was thought that 
 parasites always existed as parasites, for the simple reason that they 
 were unable to lead a free existence, even more restricted than now. 
 
 Modern investigations have taught us that there are frequently 
 stages in the existence even of the most thorough-going parasites, such 
 as the intestinal worms, when they lead a free life in water or damp 
 earth ; and also that among the thread-worms there are many species 
 (e.g., Rhabditis) that are occasionally parasitic, and capable of arriving at 
 their full development in milk, meat, and other organic substances as 
 rapidly as, if not more quickly than, in the interior of a living organism. 
 In another thread-worm (Ascaris nigrovenosa, Auct.), we have an in- 
 stance of an animal whose life-history consists of two alternate gene- 
 rations, 1 both sexually mature, which differ so much from each other 
 in structure and mode of life, that, before their genetic connection 
 had been discovered, they were referred to two distinct families. 2 
 This case, which has such an important bearing upon the meaning 
 and right understanding of the phenomenon of parasitism, will be 
 described more fully in a subsequent chapter. 3 It follows, therefore, 
 from a case like this, that certain animals, such as the larvae of many 
 flies (Miisca vowiitoria, SarcopJiaga carnaria, Anthomyia canicularis, 
 &c.), which occasionally feed upon living animals, although usually 
 found in dead putrifying organic matter, are by no means to be ex- 
 cluded from the category of parasites. If this kind of parasitism is 
 to be distinguished in any way, it may conveniently be termed 
 " occasional," in contrast to the " constant " parasitism exhibited by 
 other animals. The term " pseudoparasite," which has been fre- 
 quently, even in recent times, applied to cases of this kind, ought to 
 be confined to various objects, such as hairs, vegetable tissue, &c., 
 which have been mistaken for parasites, and even described as such; 4 
 
 1 For a fuller account see Vol. II. 
 
 2 The case mentioned in the text is not the only one known. Recent investigations 
 have shown me that Anguittula stercoralis, occurring in cases of " Cochin-China diarrhoea," 
 is the Rhabditiform generation of A. intestinalis (Leuckart, Bericht math. phys. Cl. I: 
 Sachs. Gcsdlsch. d. Wiss., p. 85, 1882). There lives also in the peritoneal cavity of Jli/lnbinx 
 pint a strange parasite, Allantonema mirabile, Lkt., whose offspring leads a free existence, 
 and gives rise to many generations of Rhabditis, like sexually mature worms (Leuckart, 
 Tagebl. d. Magdeburg. Naturf. Versamml., p. 320, 1880. R. L. 
 
 3 Chapter VIII. 
 
 4 A list of this kind of pseudoparasites, including only the commonest, would be too 
 long for insertion here. It may be remarked that all kinds of objects, not only the debris 
 of food (orange-pips, raisin-stones, sinews, small bones, and so forth), but also pieces of 
 thread, hairs, &c. , have been mistaken for parasites. It is generally not difficult to dis- 
 tinguish these by the help of the microscope. 
 
RELATION OF PARASITIC TO FREE LIFE. 3 
 
 and, in my opinion, also for frogs, snakes, and spiders, 1 which have 
 been stated by many authors to have existed for years in the human 
 alimentary canal, although it is perfectly certain that animals of this 
 kind cannot endure the damp heat of the body of a mammal for 
 more than six hours. 2 
 
 This occasional parasitism sufficiently points out what has just 
 been maintained from another point of view, that no broad line of 
 demarcation can be drawn between parasites and free-living animals. 
 
 It is not, however, in such instances alone that the transition 
 between the free and parasitic modes of existence is found. Many 
 animals (such as the leech) are only parasites so long as they obtain 
 their nourishment at the expense of larger and more powerful 
 creatures, becoming simply carnivorous when they prey upon other 
 animals of their own size or smaller. A parasite is, in all cases, 
 smaller and weaker than the animal on which it feeds. Being in- 
 capable, therefore, of overpowering it, the parasite contents itself with 
 plundering its host and drawing nourishment from its juices and flesh. 
 
 Thus the parasitic and free modes of existence are related to 
 each other in two distinct ways, both of which are connected with 
 peculiarities of parasitism itself, one of these links being the nature 
 of the food, the other the relation of the parasite to the animal which 
 supplies the nourishment. Eeflecting upon the significance, already 
 pointed out, which the size and equipment of the parasites have with 
 regard to their mode of life, it is not surprising that the various groups 
 of the animal kingdom do not all furnish equal contingents to the 
 army of parasites. Among the Vertebrata, for instance the majority 
 of which are strong and of large size there are very few parasitic 
 forms ; while, on the other hand, among the comparatively small and 
 feeble Arthropoda and worms there are entire families, all, or nearly 
 all, the members of which lead a parasitic life. In fact, it may safely 
 be asserted that these two groups contribute more parasitic forms 
 than all the other divisions of the animal kingdom taken together. 
 
 1 In these cases, also, the microscope serves to dispel the illusion ; for the contents 
 of the intestines of these pseudoparasites will contain substances that could not possibly 
 have been obtained in the body of their host. In estimating the origin of various objects 
 asserted to have been evacuated by a patient it is impossible to be too careful. In such 
 cases there is frequently an attempt to deceive the medical man, but more usually some 
 error has been introduced through a variety of circumstances. If, for instance, everything 
 that is found mixed with the faeces be, without further investigation, set down as having 
 come from the body of the patient, then the famous helminthologist, Dr. Bremser, must 
 have evacuated, as he humorously relates, a pair of snuffers ; for they were certainly 
 found in the bed-pan at a time when he was slightly indisposed, without any one having 
 placed them there. 
 
 2 Berthold, "Ueber lebende Amphibien im lebenden Korper," Mutter's Archivf. Anat. 
 u. Physiol., p. 430, 1849. 
 
4 NATURE AND ORGANIZATION OF PARASITES. 
 
 The parasites of man and the higher vertebrates belong exclusively 
 to them. 
 
 Comparing together the various forms of animal life included here 
 in the group of parasites, we find numerous and striking differences, 
 not only in structure, which corresponds of course to their zoological 
 position, but also in their biological aspects in the nature and 
 degree of the parasitism exhibited. On the one hand, there are para- 
 sites which only occasionally seek out their host, and only remain 
 long enough to take in a sufficient supply of food, departing as soon 
 as this is done, and subsequently, perhaps, seeking out a fresh host. 
 On the other hand, there are parasites that pass a considerable time, 
 perhaps a whole stage of their existence, in the body of their host, 
 which thus serves as a dwelling-place as well as a source of nutriment. 
 This difference may perhaps be best expressed by the terms " tem- 
 porary " and " stationary ;" but it must be pointed out that between 
 these two kinds of parasitism no absolute line of demarcation can be 
 drawn, any more than between the parasitic and free modes of exis- 
 tence; the terms, however, may be retained, as they express two 
 degrees of parasitism, which are, generally speaking, sufficiently 
 distinct and are sometimes widely separated from each other. 
 
 Even among the older zoologists this distinction was recognised, but 
 " temporary " parasitism was usually so called in contradistinction to 
 life-long, instead of to merely " stationary" parasitism. At that time, 
 however, the fact that even the most thorough-going parasites the 
 intestinal worms are free during part of their life, was not known, 
 and, accordingly, the contrast implied between the types of parasites 
 was different altogether from that put forward here. Besides those 
 parasites which exist as such throughout their whole life-cycle, there 
 are others which lead a free life for a longer or shorter period, either 
 in the adult condition (ichneumon-flies and gad-flies), or as larva* 
 (certain thread-worms). 
 
 " Stationary " parasitism, therefore, manifests itself in two ways ; 
 it may be (1) " permanent," lasting for life ; or (2) " periodic," 
 embracing only a stage in the life-cycle, and therefore involving at 
 some time or other a change from parasitic to free life. 
 
 The various kinds of parasitism just enumerated possess an interest 
 and importance that depend not merely upon their relations to each 
 other and to other modes of existence ; they are interesting also 
 from the fact of the influence which they have in modifying the 
 structure of the body, so that an examination of any form of parasite 
 enables one to foretell with moderate certainty the particular kind of 
 parasitism which it exhibits. Thus, temporary parasites must evi- 
 dently be provided with the means of approaching and abandoning 
 
EFFECTS OF PARASITISM. 5 
 
 their host ; they must have organs of motion and of sense. This is in- 
 variably found to be the case ; temporary parasites possess powerful 
 limbs (e.g., the bed-bug), sometimes even wings (midges and some other 
 flies 1 ), or swimming appendages (fish-louse). When present, these 
 organs allow of a more complex development of the vital activities, 
 and that, perhaps, to such a degree, that temporary parasites, when 
 away from their host, display hardly any recognisable peculiarities. 
 Only the nature of their food, and the way in which they obtain it, 
 compel us to regard them as parasites; it is not the refuse of 
 organic life, but living organisms, that supply them with nutriment. 
 
 As the power of movement becomes less, it becomes more and 
 more difficult for the parasite to leave its host. In this way a tem- 
 porary gradually changes into a stationary parasitism ; the host which 
 was formerly only visited at intervals, and for a short time, now serves 
 as a shelter to the parasite, and is seldom abandoned by it or changed 
 for another. Among stationary parasites there are many (e.g., the 
 flea) which retain the power of movement, and sometimes abandon 
 one host for another in search of a safer dwelling-place or more 
 abundant nutriment. These forms present many analogies to the 
 temporary parasites, not merely as regards their mode of life, but in 
 their structure, especially in regard to the development of locomotor 
 organs. In the majority of cases, however, the power of movement 
 is reduced in stationary parasites, sometimes entirely lost, so that the 
 animal remains for months, or even years, attached to the same host. 
 Instances of this may be found in the bladder-worms and the female 
 Lernseadse, which live with their heads imbedded in the muscles of 
 fish. Moreover, it is not only the organs of locomotion which become 
 abortive in these cases. The sense organs, and especially the eyes, 
 whose development is almost co-extensive with the variety and energy 
 of the muscular activity, in like manner frequently degenerate. The 
 graceful outline of the body and its segmentation commonly dis- 
 appear, in adaptation to the present slight need of locomotion. 
 
 In fact, a glance at the group of the so-called intestinal worms, 
 which are all stationary parasites, shows clearly that the more sedentary 
 the life of a parasite becomes, the simpler and more undifferentiated is 
 the form of the body. 
 
 Moreover, the simplification of the external structure of the body 
 is no more a special peculiarity of stationary parasites than is the 
 possession of wings and swimming feet a peculiarity of free-living 
 animals. Among the latter we find numerous examples of a similar 
 form of body, and especially among those creatures with limited 
 capabilities of locomotion, which, in this respect, are somewhat 
 
 1 Hippobosca, Ornithomyia, &c. 
 
NATURE AND ORGANIZATION OF PARASITES. 
 
 analogous to stationary parasites. I only need to mention certain 
 caterpillars and other insect larvse, many of which lead a stationary 
 life like the intestinal worms, and, furthermore, resemble them in that, 
 in many cases (e.g., ichneumon -flies, &c.), they are occasionally or even 
 constantly parasitic. Besides these negative characters, stationary 
 parasites can in many cases be recognised by positive characters, such 
 as the possession of hooks and suckers, which serve to fix them on to 
 the body of their host. Structures of this kind are by no means con- 
 fined to stationary parasites, but are also commonly found in 
 temporary parasites, and occasionally even in free-living animals, 
 where, however, they are never so conspicuous or so constantly de- 
 veloped. The more the power of locomotion in a parasite diminishes, 
 the more difficult it is for it to migrate to another animal, and it must 
 therefore be provided with organs which will enable it to retain its 
 position under the most adverse circumstances. These organs of 
 attachment vary in character, in correspondence with the structure of 
 that part of the body of the host upon which the parasite dwells, 
 being generally stronger and larger in those forms which are parasitic 
 upon the outer skin than in those which live in the interior of the body 
 of their host. Among internal parasites, again, the organs of attach- 
 ment are generally more developed in those species which live in the 
 alimentary canal, since they have to withstand the pressure of its 
 contents. Many intestinal worms, however, 
 do not possess any hooks or other organs of 
 attachment ; but in these cases there is gene- 
 rally some compensation. Among the thread- 
 worms, for example, which we shall presently 
 consider, the form and length of the body 
 seem quite as fit to break the pressure of the 
 intestinal contents as to strengthen its hold 
 upon the intestinal wall. In Trickocephalus 
 (Fig. 3) the whiplash-like anterior part of the 
 body is actually imbedded in the mucous 
 membrane. 
 
 In this case the form of the body in a 
 certain way makes up for the absence of 
 proper organs of attachment. When these 
 are present we find the greatest differences 
 in their structure and arrangement, which 
 correspond always to the needs and cir- 
 cumstances of the individual parasite. Some- 
 times, as in the flukes (Fig. 1), muscular suckers are present, which 
 work by atmospheric, or, more correctly speaking,by hydraulic pressure ; 
 
 FIG. 1. Distomuni hi- 
 tcum (young), with suckers 
 and viscera (after de la 
 Valette). 
 
ORGANS OF ATTACHMENT. 7 
 
 sometimes the organs of attachment consist of hooks and claws, which 
 serve to penetrate the underlying tissue or to lay hold of various 
 prominences. In Tcenia solium (Fig. 4) and other tape-worms these 
 hooks have their basal end sunk within the tissues of the parasite, or 
 else, as in lice (Fig. 2) and the majority of the parasitic Arthropoda, 
 they are situated upon the extremities of the limbs. The various 
 bristles and other prolongations of the outer skin, so commonly met 
 with, may be safely included in the category of organs of attachment. 
 These, by contact with neighbouring parts of the body, not only in- 
 crease the power of resistance of the parasite, but also prevent it from 
 being displaced in this or that direction, according to their disposition. 
 By the possession of setse of this kind, the male Distomum (Bilharzia) 
 kccmatobium is able not only to retain its position in the vena cava of 
 man, but also occasionally to advance against the blood stream into the 
 venous plexuses of the urinary bladder and rectum, so as to enable the 
 female, which it drags along with it, to lay its eggs in a convenient place. 
 Frequently several kinds of organs of attachment are found upon 
 the same parasite; an instance of this is Tcenia solium, which has 
 
 FIG. 2. PcdicuLus (Phtkirius) pubis. FIG. 3. Trichoccphcdus dispar, in situ. 
 
 just been mentioned. Besides the hooks which are arranged in a 
 circle upon the summit of the head (Fig. 4), there are found a number 
 of suckers, which, together with the hooks, enable it to attach itself so 
 firmly that it is very difficult to remove it from its place. Comparing 
 the four suckers and their position upon the head with the single 
 terminal sucker of the leech and the two suckers of Distomum (Fig. 
 1), we see that the organs of attachment in the parasites offer 
 quite as great differences in their arrangement as in their structure. 
 
8 
 
 NATURE AND ORGANIZATION OF PARASITES. 
 
 It has by this time, I hope, been made clear that the stationary 
 parasite differs much more from ordinary free-living animals, both in 
 the outward form of the body and in its armature, than the tem- 
 porary parasite. How great the difference really is between 
 these two forms of life, is most distinctly seen in those para- 
 sites which are free at one period of their existence, and parasitic 
 at another ; the free stage may perhaps be entirely unlike the parasitic, 
 especially in those cases where the conditions of life enjoyed by the 
 animal during its parasitic and free stages 
 differ markedly from each other. The larva of 
 Gastrus, which inhabits the stomach of the horse, 
 has all the characters of a stationary parasite ; a 
 simple cylindrical body without eyes and sense 
 organs, and, instead of organs of locomotion, 
 organs of attachment in the shape of powerful 
 hooks at both sides of the mouth, and numerous 
 variously sized setae upon the surface of the body. 
 How different is the form of the adult free-living 
 animal, with its segmented body, eyes, ten- 
 tacles, legs, and wings ! Who would believe 
 that these two creatures were merely stages in 
 the development of the same animal, had not 
 actual observation demonstrated the fact, and 
 shown that the worm-like larva was produced 
 from the eggs laid by the fly. 
 
 But this striking difference, we cannot doubt, 
 corresponds less to the needs of parasitism as such, than to the differ- 
 ences which usually obtain between a stationary mode of life *and a 
 free existence. In this way we can understand the fact, already men- 
 tioned, that metamorphoses quite similar to that of Gastrus are com- 
 monly met with in other insects, where the young are not parasitic, 
 but only live a stationary life like parasites. 
 
 Conversely, there are periodic parasites, whose structure, during 
 both stages of their life-history, is quite the same. This is the case 
 with the Gordiacese, which pass their young stage in the body-cavity 
 of snails and insects, and afterwards live in water or damp earth 
 without any further ingestion of nutriment. In this instance, how- 
 ever, there is no great difference in the manifestations of life between 
 the free and parasitic stages ; in both, the animal leads a stationary 
 existence, and it is only the medium in which it lives that changes. 
 
 It has been already pointed out in this chapter that the characters 
 of parasites cannot be said to have the value of specific peculiarities, 
 and this is well shown in certain remarkable cases of parasitism, to 
 
 FIG. 4. Cephalic end 
 of Tcenia solium. 
 
COMMENSALISM. 9 
 
 which van Beneden first applied the term " commensalism." Here we 
 have creatures that live within the bodies of larger animals, like para- 
 sites, to which they are generally very similar in organization ; never- 
 theless, they are not true parasites, inasmuch as they do not feed upon 
 the juices and tissues of their host, but share its food or live upon the 
 refuse of its body. Although there are several instances of commen- 
 salism among the lower aquatic animals, we do not find any in man 
 and the domestic animals, which form the subject of the present 
 treatise, it being supposed, of course, that the conception of the term 
 is not extended to such parasites as live upon the internal excretory 
 products, instead of the living tissues of their host. If it could be 
 definitely proved that certain intestinal worms (such as Oxyuris 
 curvula of the horse) really feed upon the undigested food of their 
 host, 1 this statement would need some limitation; but it would at 
 the same time tend to show that commensalism is connected with 
 true parasitism by numerous transitional stages, as we have already 
 seen that the free and parasitic modes of existence are connected. 
 
 1 TDujardin, Ann. Sci. Nat., ser. 3, t. xv., p. 302, 1851. 
 
CHAPTER II. 
 OCCURRENCE OF PARASITES. 
 
 JUST as there is hardly a single creature which is not preyed upon 
 by some carnivorous foe, so it seems probable that every animal gives 
 shelter at one time or another to some parasite. We are even 
 acquainted with cases where the parasite itself is subject to the 
 attacks of other parasites. Many of the parasitic Crustacea, for 
 example, give shelter to mites or thread- worms ; the parasitic larva of 
 the ichneumon-fly again is inhabited by other minute parasitic 
 larvae (Pteromalinse.) In the case of the Nematode, Trickosomum 
 crassicauda, which infests the rat, we find three or four males living 
 parasitically within the uterus of the female. 1 Neither small dimen- 
 sions nor a concealed mode of life offer the slightest protection against 
 these enemies. 
 
 Nevertheless, every animal is by no means equally subject to the 
 attacks of parasites ; on the contrary, we find the greatest differences 
 in this respect. In certain animals, the presence of parasites appears 
 to be the rule, since they may be found in great abundance 2 in every 
 individual examined ; in certain others hundreds of specimens may 
 be searched without finding a single parasite. On the whole, it may 
 be safely stated that the Vertebrata are far more generally infested by 
 parasites than the Invertebrata, and indeed it was thought for a long 
 time that their occurrence in the latter was a mere accident. Which- 
 
 1 See Vol. II. The recent researches of Biitschli and von Linstow have fully de- 
 monstrated this fact. Moreover, there is another free-living worm (Boncttia), the male 
 of which in a similar fashion lives within the genital duct of its own female. See 
 Kowalewsky, " Du male planariforme de la Bonellia," Revue dcs Sci. Nat., pL iv., 1875 
 (translated from the Russian); Vejdovsky, Zeitochr. f. wiss. Zool., Bd. xxx., p. 487, 
 1878 ; Spengel, MittlteU. zool. Stat. Xeapel, Bd. i., p. 357 et seq. 
 
 3 The snipe, the goose so long as it lives in meadows the turbot, have their 
 intestines almost always filled with numerous Helminths, generally Cestodes. How vast 
 is occasionally the number of parasites is shown by certain cases of trichinosis and the 
 Cochin-China diarrhoea. Even the larger intestinal worms are sometimes found in great 
 numbers. Bloch (" Abhandlung von der Erzeugungder EingeweidewUrmer," Berlin, 1782, 
 p. 12) found in a male bustard at least a thousand specimens of Tcenia rillosa, some of 
 which were no less than 4 feet in length. Goze also (" Versuch einer Naturgeschichte 
 der Eingeweidewurmer," 1782, p. 32, note) found the alimentary canal of a parrot so full of 
 Cestodes, 20 ells in length and about the thickness of a straw, "that it (intestine) was 
 almost ready to burst." When the whole mass was placed in water, Goze was astonished 
 
ABUNDANCE OF PARASITES. 11 
 
 ever opinion may be held whether we regard the presence of parasites 
 in invertebrates as a necessary preliminary to their sojourn in the 
 body of some vertebrate or not the fact remains the same. The 
 abundance of parasites within the Vertebrata may be more or less 
 accounted for by the fact that there are normally several, if not a 
 great number of species found in the same host. 1 Thus, for example, 
 man has more than fifty distinct species of parasites, the dog and the 
 ox some two dozen each, the frog perhaps twenty. These are of 
 course not all found in the same place and under similar condi- 
 tions, but are scattered throughout the various organs and systems. 
 One takes up its abode in the skin, another in the intestines, 
 a third in the connective tissue between the muscles, while others 
 again inhabit the brain or even the eye. No organ or tissue, how- 
 ever remote or concealed, is entirely free from parasites, and it is 
 well known that even the embryo within the body of the mother is 
 occasionally infested by them. What has been already said about the 
 various species of animals, applies equally well to the different 
 organs ; some are more liable than others to be inhabited by parasites. 
 The outer skin of the body and the alimentary canal seem on the 
 whole to contain the greatest number, and this because they are 
 more easy of access: in man more than three-fourths of the total 
 number of parasites are found in these two localities. 
 
 Frequently the distribution of a given parasite is not confined to 
 a single organ. There are numerous examples, however, of this e.g., 
 Trichina spiralis, when encysted, is found only in striated muscle, 
 the sexually mature Cestodes and Echinorhynckus are confined to the 
 intestines, and Phthirius piibis only inhabits those parts of the body 
 that are thickly covered with hair ; but the converse is almost more 
 general. Cysticercus celhdosce, for instance, infests the intermuscular 
 
 at the enormous number, for there were several thousands. This same helminthologist 
 found on another occasion no less than 82 Ligutce in the intestines of a diver, 
 some of which were 6 to 8 ells long and 8 lines broad. Frequently the intestinal worms of 
 an animal belong to several different species. Nathusius ( A rchivf. Naturyesch., Jahrg. iii., 
 Bd. i., p. 53, 1837), took from a single black stork 24 specimens of Filaria labiata from the 
 lungs, 16 Syngamus (Stronyylus) trachcalis from the trachea, more than 100 Spiroptera alata 
 from the coats of the stomach, several hundred Holostomum excavatum from the small 
 intestine, and about a hundred Distoma ferox from the intestine, 22 specimens of Distoma 
 Itians from the oesophagus, 5 Distoma ( D. hians ?) from between the coats of the stomach, 
 and 1 Distoma echinatum from the small intestine. This forms quite a helminthological 
 museum ; but Krause of Belgrade found even a greater number in a horse two years 
 old over 500 Ascaris mcyalocephala, 190 Oxyuris curvula, several millions of Slronyylus 
 Mracantlius, 214 Sclerostomum arrnatum, 69 Tcenia perfoliata, 287 Filaria papillosa, and 
 6 Cysticerci f (See van Beneden, "Animal Parasites," p. 91.) 
 
 1 Von Linstow has recently published a useful compilation of the distribution of 
 Helminths, which is the most complete in existence : " Compendium der Helminthologie, " 
 Hanover, 1878. 
 
12 OCCURRENCE OF PARASITES. 
 
 connective tissue, the brain and eye, and many other localities; 
 Echinococcus is found in the liver, spleen, kidney, lung, bones, nervous 
 centres, beneath the skin, and, in short, almost everywhere in the 
 human body. Similarly Filaria papillosa of the horse is not only 
 found in the peritoneal membrane, but also in the peripheral connective 
 tissue of various parts of the body, and occasionally in the body-cavity, 
 inside the skull and vertebral column, sometimes even in the eye, 
 either in the outer layers, the anterior chamber, or the vitreous body. 
 The same principle holds good in regard to the relations of a 
 parasite to its host. Some species are limited to a single host ; others, 
 again, are parasitic upon several animals, not merely at different 
 periods of their existence passing their youth in the body of one 
 animal, and attaining their maturity in that of another but also 
 during the same phase of development. In the first group may be 
 reckoned among human parasites, Pediculus capitis, Bothriocephalus 
 latus, and Oxyuris vermicularis ; also Tcenia crassicollis of the cat, and 
 Echinorhynchus gigas of the pig. To the second group belong by far 
 the greater number of parasites, such as Strongylus gigas, which is 
 found in many Carnivora in the genera Canis, Mustela, Nasua, 
 &c., in the horse, the ox, and in man ; Trichina spiralis, which 
 not only infests man, the pig, and the rat, but also the hedgehog, 
 fox, martin, dog, cat, rabbit, ox, and horse, and may be trans- 
 planted even to birds. Distomum hepaticum has also a very wide 
 distribution among warm-blooded animals, being found in most Rumi- 
 nantia, Perissodactyla, Pachydermata, and Rodentia, and also in the 
 kangaroo, in man, &c. Although it is a general rule that a para- 
 site infests several distinct animals, it is equally true that the 
 distribution of parasites is governed by certain laws. The examples 
 just cited show this clearly. The various animals which are infested 
 by one and the same parasite are always more or less closely related 
 to each other. It is most usual to find that the related species of a 
 given genus, or the genera of a given family, harbour the same para- 
 sites ; there are, indeed, only very few exceptions to this rule, such as 
 Trichina spiralis. But even in these rare cases a certain relation can 
 be observed between the different hosts ; and a parasite which in the 
 same stage of its existence infests sometimes a mammal or a fish, 
 sometimes a mollusc, is quite unknown. This fact becomes more 
 evident when we examine not merely the number of hosts in which 
 a given parasite is met with, but also the statistics of the distribution 
 of parasites, and discover the number of times which it is found in 
 each host ; for instance, in other words, Distomum hepaticum is only 
 rarely found in man, the kangaroo, and rodents, while it is commonly 
 met with in ruminants, especially in the sheep. The same holds good 
 

 RESPIRATION OF PARASITES. 13 
 
 in the case of Strongylus gigas, which is far more abundant in car- 
 nivorous than in herbivorous animals, while it has only been met with 
 a few times in man and other hosts. By the help of the statistical 
 method it is easy to find out what are the animals most frequented by 
 a given parasite, and the results obtained show that the several hosts 
 are always more or less allied to the one in which the parasite is 
 most commonly found. The causes of this are no doubt various, and 
 partly of a kind which will be discussed later on, when we come to 
 examine into the life-histories, origin, and migrations of parasites ; 
 but for the present it may be remarked that these causes are to be 
 looked for partly in the hosts themselves (in their distribution, habits, 
 manner of locomotion, and their food), partly also in the nature, con- 
 dition, and needs of the parasites. 
 
 The factors which we are considering now are nearly the same as 
 those which govern the relations between carnivorous and herbivorous 
 animals, inasmuch as they concern not merely the actual carnivorous 
 instinct, but also the choice of the prey. We need not be surprised, 
 therefore, that a carnivorous mode of life, as has been already pointed 
 out, is unmistakeably related to a parasitic mode of life. 
 
 A very cursory examination of the conditions of life proves that 
 we are right in regarding the distribution of parasites as greatly de- 
 pendent upon the nature of the host as well as of the parasite itself. 
 It is clear, for instance, that a parasite with lungs and other organs 
 that need a direct contact with the air, can only exist in those 
 creatures whose structure and mode of life render this possible, and 
 only in those parts of the body to which the air has free access. Thus, 
 all parasitic air-breathing insects (including Arachnida) are, without 
 exception, confined to terrestrial or amphibious animals, and generally 
 to their external skin. The walrus, for example, harbours a Pedicidus 
 of considerable size. On the other hand, the external parasites of 
 aquatic animals generally belong to the Crustacea or some group 
 which breathes by means of gills, and therefore needs direct contact 
 with water. Worms breathe by means of the skin, and hence the 
 parasitic members of this group the so-called Helminths are some- 
 times found as ectoparasites upon aquatic animals, while they are 
 usually met with only in the interior of terrestrial animals, in organs 
 where they are bathed in the oxygenating fluids of their host. Para- 
 sitic worms are also found in similar situations within the bodies of 
 aquatic animals, but this is quite intelligible, inasmuch as they are 
 of all parasites the most widely diffused ; in fact, internal parasites, or 
 " Entozoa," as they are usually termed, are mainly worms. 
 
 With this wide distribution may be coupled the fact that parasitic 
 worms are numerically far more abundant than parasitic Arthropoda ; 
 
14 
 
 OCCURRENCE OF PARASITES. 
 
 the -latter, moreover, live in comparatively similar circumstances, 
 while the conditions of entoparasitism are most varied. 
 
 It must not be forgotten, however, that there are a few entoparasi- 
 tic Arthropoda belonging to the Insecta and Arachnida. The most strik- 
 ing example is furnished by the Pentastomida (Fig. 5), which, during 
 the early stages of their existence, inhabit the internal organs of both 
 terrestrial and aquatic animals, and on this account were included by 
 the earlier helminthologists among the Helminths proper. A closer in- 
 vestigation has shown that this classification, though hardly to be 
 wondered at, is erroneous ; the Pentastomida are undoubtedly to be re- 
 ferred to the Arachnida, but they differ from them by the entire absence 
 of lungs, and in this respect approach the intestinal worms. Many 
 mites also (Fig. 6) possess no respiratory organs, and agree with the Pen- 
 tastomida in breathing by means of the skin ; this is facilitated by their 
 small size, which implies a relatively large surface, and by the fact that 
 they are usually to be found in damp situations, sometimes imbedded 
 in the epidermis (Sarcoptes}, almost entoparasitic, sometimes upon the 
 hairy portions of the skin (Dermatodectes, &c.). But these instances 
 must not be considered as proving that all entoparasitic Arachnida and 
 
 FIG. 5. Pentastomum denticulatum from 
 the liver of man. 
 
 FIG. 6. Sarcoptes srablti. 
 
 Tnsecta differ from their immediate allies by the absence of respiratory 
 organs. On the contrary, the majority possess the normal tube-like 
 
AIR-BREATHING ENTOZOA. 
 
 15 
 
 lungs (the so-called " tracheae "), and need therefore a direct contact with 
 the air. To understand this properly, we must remember that contact 
 with the air is by no means confined to the outer surface of the body ; 
 many of the internal organs are either continuously or occasionally in 
 communication with the outer air ; and all these organs, in spite of 
 their position in the interior of the body, are occasionally inhabited by 
 air-breathing parasites. 
 
 We often find the larvae of flies within the nose and frontal 
 sinuses of mammals, especially the sheep (Oestrus ovis) ; sometimes, as 
 has been recently reported from Guiana, in man himself (Lucilia 
 hominivora and Sarcopliaga WoMfarti, both belonging to the Musci- 
 dae) ; the larvae of flies (Musca vomitoria, Anthomyia canicularis, Figs. 
 7 and 8) are also sometimes found in the intestine, especially in its 
 interior portion, where air frequently enters along with the food ; in- 
 deed the larvae of G-astrus equi are almost constantly found in the 
 horse in this situation. Other air-breathing parasites live below the 
 skin of mammals (as the larvae of Oestrus and the chigoe), and dwell 
 not in enclosed spaces, but in passages open to the air ; in these cases 
 the apertures of the respiratory organs of the parasite are generally 
 turned towards the exterior, to permit of a free exchange of air. Simi- 
 larly, in parasitic larvae within the body-cavities of insects, the hinder 
 
 FIG. 7. Larva of Anthomyia canicularis 
 from the intestine of man. 
 
 FIG. 8. Larvae of Musca vomitoria. 
 
 portion of the body with its tracheal opening is usually (as in the 
 chigoe) protruded through the outer skin of its host, or is in com- 
 munication with the tracheae of the latter. The occasional presence 
 of dipterous larvae in wounds, abscesses, even in the vagina, and under 
 the praeputium and eyelids, is well known, and is easy to understand, 
 
16 OCCURRENCE OF PARASITES. 
 
 after what has just been said, since these parts of the body, being on 
 the outside, are precisely the situations most convenient to parasites 
 of this kind. Where respiration is impossible, there can evidently be 
 no air-breathing parasites, and all notices of fly-larvae discovered in 
 such situations, as for example, within the internal urinary passages, 
 are to be regarded as mere fables. The absolute need of access of air, 
 which parasites of this description have, can be easily proved by 
 experiment. I have frequently introduced the larvae of Musca vomitoria 
 at all stages, even as eggs, into the body-cavity of dogs and rabbits 
 through apertures in the abdomen, but never in a single instance 
 observed any further development take place; in most cases they 
 died very shortly. 
 
 From the foregoing remarks, it follows that parasites may be 
 divided into two groups ectoparasites (Epizoa, external parasites) 
 and entoparasites (Entozoa, internal parasites). I am well aware that 
 in certain cases this distinction is not more easy to make than that be- 
 tween internal and external organs, and that the two groups by no 
 means include all the peculiar forms of parasitic life ; but it is on the 
 whole convenient to retain it, to express the general conditions of 
 parasitism with which we are for the present concerned. 
 
 The ectoparasite inhabits the most readily accessible organs of the 
 body of its host, which it frequently abandons at pleasure. The group 
 which we have already alluded to as temporary parasites are, with a 
 few exceptions, ectoparasitic. In the same way, the semi-stationary 
 parasites are usually found upon the outer skin, where the least 
 hindrance is offered to their movements, while the entirely stationary 
 parasites are more commonly met with in the internal organs. It 
 follows, therefore, that ectoparasites can generally be recognised as 
 such by their outward form, especially by the structure of their 
 organs of locomotion. 
 
 In certain ectoparasites, which have but a slight locomotive capa- 
 city, there are usually found, either upon the organs of locomotion 
 (Fig. 2), or (as in ectoparasitic worms) in their stead, powerful organs 
 of attachment, which are generally more strongly developed than in 
 the Entozoa. These structures enable them to cling very firmly, and 
 prevent them from being detached by the movements of the animal 
 upon which they live. The great differences that exist between these 
 organs in different parasites are greatly dependent upon the mode of 
 life of their host and the structure of its outer skin. 
 
 With regard to respiration, the ectoparasite, as has been already 
 remarked, depends upon its host, and shares with it the same condi- 
 tions of life. It usually possesses special organs of respiration, especially 
 when living upon terrestrial animals, and being, therefore, in direct 
 
ORAL APPENDAGES ENTOZOA. 17 
 
 contact with the air. The possession of these organs is an almost 
 exclusive attribute of ectoparasites ; for the Entozoa belong, with a few 
 exceptions, to the group of worms which breathe by means of the skin. 
 The Entozoa, besides having no special respiratory organs, are also with- 
 out pigment, the skin being whitish and transparent : in this they agree 
 with many other creatures, which, like themselves, are removed from the 
 influence of light. The ectoparasites, on the other hand, especially the 
 temporary parasites, agree in these respects with free-living animals. 
 
 The modifications undergone by parasites, to adapt them to the 
 various conditions, are also to be noticed in the structure of the 
 mouth organs. 
 
 Parasites upon the outer skin, of the higher Vertebrata at any rate, 
 can obtain no other nutriment than a more or less firm horny sub- 
 stance belonging partly to the epidermis and partly to the struc- 
 tures that originate from it ; it is needful, therefore, that they should 
 possess some apparatus strong enough to gnaw through these hard 
 tissues, and this we find, in the form of powerful jaws, in many lice, 
 and especially in the Mallophaga. In the same way, parasites that 
 feed upon the blood of their host must be able to bore through its epi- 
 dermis, in order to reach their food and then suck it up. In these 
 cases we find either mandibles, surrounded by a circular lip that plays 
 the part of a sucker, as in the leech (Fig. 9), or a boring apparatus, as 
 in the common lice, bugs, fleas, and mosquitoes, 
 which has the advantage of working rapidly, and 
 is therefore specially adapted to these parasites 
 which only visit their host for a short time. 
 
 The necessity of a special mouth apparatus can 
 only be dispensed with in those ectoparasites that 
 live upon an animal which has a soft skin, as is 
 generally the case in aquatic animals. The para- 
 site, then, is provided with some contrivance that 
 enables it to suck; generally a pharynx, or some F i G .9.-^phalicend 
 muscular apparatus which allows of an alternate of Hirudo medidnaiis, 
 
 . , . , , n i_i J.T , with the three mandibles 
 
 widening and narrowing ot the mouth cavity, or at the base of the oral 
 which under other circumstances may cause merely CU P- 
 a peristaltic action. 
 
 The Entozoa generally possess some apparatus of this kind in 
 contradistinction to the ectoparasites, and are but rarely provided 
 with jaws like the latter, except in a few cases, such as Uochmius duo- 
 denalis (Fig. 10), which, although parasitic in the intestine, lives upon 
 the blood of its host, and not upon the epithelial lining or contents 
 of the intestine ; and is in this respect, therefore, analogous to an 
 ectoparasite. Since most entoparasites are entirely nourished by 
 
18 
 
 OCCURRENCE OF PARASITES. 
 
 the fluid or semi-fluid substances which surround them, the presence 
 of the above-mentioned sucking organs is quite intelligible ; they are 
 
 FIG. 10. Cephalic extremity of Dochmius duodenaJis ; 
 profile and front view. 
 
 not, however, absolutely necessary. Many 
 Entozoa have no muscular pharynx, and are some- 
 times even entirely destitute of an alimentary 
 canal, and must absorb their food through the 
 surface of the body, after the fashion of a plant, 
 without the action of any further process. 
 The Cestodes and Echinorhynchus belong to 
 this class, and their outer skin possesses the 
 requisite permeability to a high degree, as may be 
 easily proved by placing the animals in water, 
 when they swell up rapidly. Of course, it is 
 only substances dissolved in fluids that can 
 find their way into the interior of the bodies 
 of these parasites ; but they usually live in situ- 
 ations where they are surrounded by nutritive 
 fluids to such an extent that they may be re- 
 garded as almost swimming in them. 1 In all 
 probability, this way of taking in nutriment by 
 endosmosis is not confined to the anenterous 
 
 FIG. 11. A male Echi- , . , ,, ^ , 
 
 norhynchus angustatus. ^Tms y but exists generally among Entozoa, 
 (The internal organs con- though it undergoes various modifications in 
 
 sist of the sheath of the .,, , ,., 
 
 proboscis, with retractor correspondence with the various differences of 
 muscle, lemniscus, and structure in the outer covering of the body. 
 
 sexual organs. An in- .^ ., . . . Al -rT , 
 
 testine is wanting.) From this point of view, the Entozoa may be 
 
 1 In the Rhizocephalida (Sacculina, &c.) we have recently discovered a group 
 of ectoparasitic Crustacea that have no alimentary canal. They obtain their food 
 like plants, by a number of branched prolongations, which pass through the body of their 
 host and ramify in its intestine. They are found generally on the ventral surface of the 
 abdomen of crabs. With respect to these interesting parasites see especially Kossman, 
 " Suctoria and Lepadidae : " Heidelberger Habilitationsschrift, 1873. 
 
ENCYSTATION OF ENTOZOA. 
 
 19 
 
 regarded as really an integral part of their host ; they are quite com- 
 parable, in respect of the way in which they are nourished (and 
 breathe), with a cell, or an embryo. They manufacture their food in 
 a precisely similar manner out of the juices surrounding them, which, 
 by chemical change, minister to the conditions of their life and growth 
 and remove their waste products. 
 
 The presence of a mouth and intestine is not, however, rendered 
 superfluous by the universality of this method of taking in food by 
 endosmosis ; they not only enable their possessor to feed upon other 
 semi-fluid or solid matters, 1 but also serve the purpose of increasing 
 the absorbent surface in cases where solid food-matter is not utilised. 
 
 All that has been said hitherto refers to Entozoa that live in 
 absolute contact with the tissues of their host, which is generally, 
 but by no means always, the case. In the parenchymatous organs, a 
 membranous cyst usually surrounds and isolates the parasite, with 
 which it has no direct connection. It is a part of the infected organ, 
 a hypertrophy of the surrounding connective tissue, which gradually 
 encloses the parasite completely; a similar cyst is, indeed, formed 
 round other foreign bodies introduced into the organ, and becomes 
 very like a serous membrane, owing to the development on its free 
 surface of a more or less thick epithelial layer (endothelium). 
 (Figs. 12-14) 
 
 FIG. 12. Cysticercus p isiformis 
 (young). 
 
 FIG. 13. Eckinococcus. 
 
 This capsule is regarded, and no doubt rightly, as an organ for the 
 protection of the infected part ; but, at the same time, it must not be 
 
 1 How great an influence the quality and abundance of the food has upon the parasite 
 is strikingly shown in the case of Polystomum integerrimum. This Trematode usually 
 inhabits for a short time the gill cavity of tadpoles, and then wanders into the bladder, 
 where it becomes sexually mature in about four years ; if it remain longer in the branchial 
 cavity, it only takes twenty-seven days to reach sexual maturity . It is not merely the 
 
20 OCCURRENCE OF PARASITES. 
 
 forgotten that it is of no less importance for the nourishment of the 
 contained parasite. The blood-vessels which traverse the capsule, 
 and occasionally form a definite system with afferent and efferent 
 vessels, supply fluid nutriment, which is absorbed by the parasite 
 through its mouth or skin, and which varies in quality according to 
 the structure of the capsule. On the whole, it appears that worms 
 encysted in parenchymatous organs do not receive a great deal of 
 nutriment, since they often remain unchanged for years, and even 
 longer periods, while the same worms, under other circumstances 
 by migration to the intestine, for instance rapidly grow and undergo 
 further development This capsule is most conspicuous in the so- 
 called bladder-worms, especially in those which grow to a large size, 
 and inhabit organs rich in connective tissue. In these cases (Echino- 
 coccv.s) the cyst becomes occasionally several millimetres in thickness, 
 and so firm that it can be easily removed without injury from the 
 
 surrounding parenchyma. (Fig. 13.) 
 Traces of a cyst are, however, found 
 in all worms which remain for any 
 length of time in parenchymatous 
 organs, even when they only attain 
 to a small size. In these cases, how- 
 ever, the hypertrophy of the con- 
 nective tissue, caused apparently by 
 the irritation set up through the 
 presence of the parasite, can hardly 
 Fio. 14. Sclerostomum tetracanthum, be recognised as a continuous (inde- 
 
 encysted. pendent) cyst. 
 
 Many worms which inhabit parenchymatous organs secrete on the 
 inner surface of their connective tissue capsule a cuticular cyst, which 
 is, of course, sharply marked off from the former by its histological 
 structure. 
 
 It appears in the form of a homogeneous membrane, consisting of 
 concentric layers ; it resists the action of alkalies, and belongs, ap- 
 parently, to the chitinous formation so generally met with in the 
 lower animals. 1 This chitinous cyst is most usually found in the 
 Trematodes, but is not wholly absent in the other groups, being 
 found, for example, in Tetrarhynclius> which lives in fishes, and even 
 in the muscle- Trichina (Fig. 15), the cysts of which are nothing 
 
 rapidity of development which characterises these individuals ; they differ also from the 
 common form in a number of anatomical peculiarities, notably by the absence of copulatory 
 organs. See the interesting observations of Zeller, Zetischr. f. wiss. Zod., Bd. xxvii., p. 
 238 et seq., 1876. 
 
 i Waldenburg is of opinion that this chitinous capsule is in some cases formed by 
 the host. See Archivf. pathd. Anat. u. Physiol., Bd. xxiv., p. 157, 1862. 
 
CALCAREOUS CYSTS. 
 
 21 
 
 else than a calcareous excretory product of the worm itself, on the 
 outside of which there lies the connective tissue capsule. 
 
 
 FIG. 15. TVicta'na-capsule, with connective tissue covering 
 (in situ), in B calcified. 
 
CHAPTER III. 
 
 THE THEOEY OF THE ORIGIN OF PAEASITES 
 REGARDED HISTORICALLY. 
 
 WERE the parasites infesting animals confined to those which are 
 temporary and external, their origin and descent would present no 
 difficulties to the observer. But numerous forms are found deep 
 in the interior of living bodies, in the brain, kidneys, and other 
 apparently inaccessible organs. It is very surprising, when we 
 expect to meet with only the blood, nerves, and other constituent 
 tissues of the body, to find independent living animals, frequently 
 of large size, which have left no trace to show how they 
 reached their dwelling-place, and, indeed, are often incapable of 
 moving about. Under these circumstances, we can easily understand 
 that the presence of parasites has an unusual interest, and that their 
 origin was one of the subjects most eagerly investigated by biologists. 
 The importance of parasites from a medical as well as from a 
 zoological point of view, caused both physicians and naturalists to 
 examine more closely into these facts, which appeared as mysterious 
 and incomprehensible as the origin of life itself. 
 
 In its most general aspect, the question of the origin of internal 
 parasites can be answered only in two ways; either they originate in the 
 tissues in which they are found, or else reach them from the external 
 world. In the former case, they must be spontaneously generated ; in 
 the latter they may, after the ordinary method, be developed from 
 fertilised ova. Indeed, all the conjectures and hypotheses as to the 
 origin of Entozoa brought forward in former centuries can be reduced 
 to these two theories, though the greatest diversities, depending partly 
 upon the views current at the time, and partly upon individual 
 opinions, are to be seen in the way in which these theories were 
 stated. Where facts are silent, there imagination is the more 
 eloquent ; and it is only in our time that a definite solution has been 
 put forward as to the origin of parasites, which rests at the same time 
 time on a firm basis of fact. 
 
 As~long as it was believed that a " generatio cequivoca" or 
 " spontaneous generation," as it is usually termed, was a pheno- 
 menon commonly met with among the lower animals, the origin 
 
ORIGIN OF INTESTINAL WORMS. 23 
 
 of intestinal worms could be readily explained. They were a 
 striking instance of spontaneous generation, the existence of which 
 was already contended for in by far the greater number of the 
 lower animals. At most, the discussion related to the particular 
 formative material out of which the newly created organism was 
 made, and whether it was first an egg or appeared at once as 
 an adult. Sometimes it was the blood and juices of the body, at 
 another time the excretions of the alimentary canal or the digested 
 food, that was supposed to be the formative substratum of the 
 spontaneous generation ; and it was disputed as to whether fermenta- 
 tion or putrefaction, or a special organizing principle, gave the first 
 impulse to its creation. 
 
 These were the opinions held by the Ancients, and throughout the 
 Middle Ages, so fruitless in scientific research. It was not until the 
 seventeenth century that the theory of the generation of animals was 
 reformed, and at the same time an entire revolution in the opinions as 
 to the origin of Entozoa inaugurated. 
 
 The researches of Swammerdam and Eedi had the most profound 
 influence, and entirely contradicted the earlier theories, that sexual 
 generation was confined to the higher animals. They showed that 
 sexual generation, precisely similar to that of birds, mammals, &c., 
 was found in many of the lower animals ; such as the insect, whose 
 development and metamorphosis were for the first time worked out by 
 these two naturalists ; not even the parasitic insects being neglected. 
 
 Eedi clearly proved by his researches and experiments that the 
 maggots, which had been formerly considered as independent organ- 
 isms (Helcophagi), were in reality the larvse of flies, and that they were 
 only developed when the fully formed insects were allowed access to 
 deposit their eggs. 1 Swammerdam, in the same way, showed that lice 
 were developed from eggs ; 2 he was also well aware (according to the 
 communications of the painter 0. Marsilius) that the parasitic larvse 
 in caterpillars were the offspring of insects that were in the habit of 
 laying their eggs beneath the skin of these same caterpillars. 3 
 
 With respect to the intestinal worms, neither of these observers 
 brought any direct evidence against the generally received opinions. 
 Certainly not Eedi, who put forward a view as to their origin, 
 which differed only by a somewhat metaphysical tinge from the 
 widely spread theory of generatio cequivoca. Swammerdam expressly 
 guards against any application of his experiments concerning the 
 development of insects to the Entozoa. It appears, indeed, as if he 
 
 1 Redi, " Esperienze intorno agl' insetti," t. i. p. 23 : Venezia, 1712. 
 
 2 "Bibel der Natur" (aus dem Hollandischen Ubersetzt), p. 37, 1752. 
 8 Ibid., p. 28L 
 
24 THEORY OF THE ORIGIN OF PARASITES. 
 
 chiefly wished to prevent it from being thought that intestinal worms 
 were derived from insects and other free-living animals ; nevertheless, 
 he does not deny the theory that they originate from the eggs of 
 species " that have already existed in the intestines of other animals." 
 
 But in spite of the anathemas which Swammerdam hurled against 
 the theory of the heterogeneous development of the Entozoa, this 
 theory shortly after was very generally accepted. 
 
 While, on the one hand, the existence of sexual generation in 
 animals was being shown to be more and more universal, and became 
 more definite, the microscope, newly applied to scientific researches, 
 revealed a whole host of minute creatures, which, in spite of their wide 
 distribution, had hitherto escaped attention on account of their small 
 size. Animalcules were found in drinking water and in food, in 
 the earth, and were supposed to exist even in the air: was it not 
 natural that under the influence of these discoveries the theory of the 
 heterogeny of Entozoa fell upon a fruitful soil ? The introduction of 
 these creatures into the human body appeared almost inevitably to 
 lead to the conclusion that, when acted upon by the warmth and 
 abundant nutriment in the body, they increased in size and became 
 veritable Entozoa. It is not surprising, therefore, that men like 
 Boerhaave * and Hoffmann 2 traced back the Cestodes and Nematodes 
 to animals which, when existing in the free state, were totally 
 different in appearance. The creatures that were supposed to be the 
 progenitors of the Entozoa were by no means the Infusoria alone, but 
 sometimes other larger creatures, such as free-living worms, and 
 specially such worms as possessed a superficial resemblance to the 
 Entozoa. Although a theory of this kind appears to us now entirely 
 unscientific, we must not forget that at that time discoveries in the 
 metamorphosis of animals were too recent and incomplete to allow of 
 a just appreciation of the law of stability of species and their cyclical 
 development. 
 
 The actual nature of parasitic worms did not long remain unknown. 
 Not only did naturalists gradually come to see that the occasional 
 change of free-living animals into Entozoa was in entire contradic- 
 tion to the common phenomena of generation and development, but 
 they learnt to recognise the Entozoa as sexual animals, whose organic 
 structure marked them out as representatives of special classes of 
 animals. 
 
 At the same time, however, it appeared that these creatures did 
 not exist exclusively as Entozoa, but that they were also capable of a 
 free existence. By a careful and systematic examination of our rivers 
 and streams, a number of animal forms were discovered that appeared 
 
 1 " Aphorism.," 1360. a " Opera," t. iii., p. 490. 
 
ORIGIN FROM FREE-LIVING ANIMALS. 25 
 
 strikingly like the Entozoa, and sometimes were even actual Entozoa. 
 Of special import was the discovery of a tape-worm in fresh water by 
 Linne, 1 and subsequently by several other naturalists in different 
 places. We now know that this tape-worm (Botliriocephalus v. Rchisto- 
 cephalus solidus) inhabits originally the body-cavity of the stickleback, 
 which it abandons at a certain stage of its development, and passes 
 some time in the water, being finally swallowed by a water-fowl. 2 
 Linne, however, did not know these facts, and regarded the worm 
 without hesitation as a young and incomplete specimen of the large 
 human tape-worm (BothriocepTialus latus), and believed, therefore, 
 that this worm was conveyed into the body from the exterior, where it 
 already existed fully formed, in water. Moreover, this assertion was 
 not confined to the tape-worm ; Linne believed that he had also dis- 
 covered the liver-fluke of the sheep and the Oxyuris of man leading 
 a free existence ; but there is no doubt that he mistook a Planarian 
 for the former and one of the free-living Anguillulidae for the latter. 3 
 
 However small the evidence was, it appeared sufficient to esta- 
 blish this idea, which was believed in by many naturalists after 
 Linne, chiefly because the facts known at that time about the 
 Entozoa, as well as other parasites which we shall have to consider, 
 were extremely fragmentary. To illustrate the small degree in which 
 helminthology was known at that time, it may be mentioned that in 
 spite of the vast numbers of existing Entozoa, not more than a dozen 
 and these almost entirely human parasites had been described. 
 
 Soon after this commenced a new era in helminthology. The 
 knowledge of intestinal worms, which was till then chiefly of medical 
 interest and cultivated by medical men, gradually began, under the 
 influence of the Linnsean school, to attract the attention of zoologists. 
 Men of high ability and wide knowledge, like Pallas, 0. F. Miiller, 
 and others, bestowed upon this science their special attention, and 
 increased our knowledge of parasites in all directions. But every 
 new parasite and new host rendered less probable the idea of Linnd 
 that these animals lived sometimes freely and sometimes as parasites. 
 
 The number of known Helminths soon became very considerable, 
 but all attempts to find them living in a free state were in vain, 
 
 1 " Amoenit. Acad.," t. ii., Erlangae, 1787, p. 93. 
 
 2 Steenstrup, Overs. K. dansk. Videnskab. Selsk. Forhandl., p. 166, 1857 : Zeitschr. d. 
 yesammt. Natunciss., Bd. xiv., p. 475, 1859. In a similar manner Ligula frequently 
 leaves the body of the fish in which it is parasitic at a certain stage of its development, 
 and leads a free life, see Bloch, " ^.bhandl. von der Erzeugung der Eingeweidewiirmer," 
 p. 2, 1782. 
 
 a " Systema Naturae," ed. x., t. i., p. 648. Fasciola hepatica, "habitat in aquis dul- 
 cibus ad radices lapidum, inque hepate pecorum." A scar is vermicidaris, "habitat in 
 paludibus, in radicibus plantarum putrescentibus, in intestinis puerorum et equi." 
 
26 THEORY OF THE ORIGIN OF PARASITES. 
 
 and yet no locality was left unsearched ; and gradually arose the 
 conviction that the statements of the free existence of intestinal worms 
 were, in the majority of cases, based upon a confusion of these worms 
 with others closely resembling them, and that in those instances (e.g., the 
 tape-worm found by Linne), where an intestinal worm appeared to 
 have been found living free, the discovery could not be interpreted in 
 the sense Linne supposed. 
 
 A new theory took the place of the old one. Basing his opinion 
 upon the facts that the eggs of intestinal worms are expelled with the 
 faeces of the animal in which they live, sometimes enclosed in a por- 
 tion of the body of their parent, as in the Cestodes, and that they 
 remain unaltered for a long time in water, Pallas * put forward the 
 view that Entozoa agree with other animals in originating from eggs 
 which can be carried from one animal to another. " It cannot be 
 doubted," he says, " that the eggs of the Entozoa are scattered abroad 
 and undergo various changes without loss of vitality, and that im- 
 mediately they reach the body of a suitable animal, through the 
 medium of its food or drink, they grow into worms." Of course the 
 eggs in this way could only reach the alimentary canal ; but since the 
 Entozoa were found not only here, but also in other organs liver, 
 muscles, brain the only possible explanation was that the eggs 
 entered the blood-vessels from the intestine, and were carried " by 
 the blood stream " to those various and apparently inaccessible organs. 
 By the help of the blood-vessels, Pallas believed that the eggs 
 occasionally reached the body of the embryo before it was born ; in 
 this way intestinal worms could also be inherited by one host from 
 another. 
 
 This was not, however, the first time that the theory of the 
 "inheritance of Entozoa" had been propounded. Even in the 
 days of Leeuwenhoek, Yallisnieri * had endeavoured to explain 
 the presence of Entozoa by supposing them to be transmitted 
 from parents to children ; and this hypothesis had many supporters, 
 including certain of his illustrious contemporaries (Hartsoeker, 
 Andry, &c.) and numerous later heiminthologists, as 0. F. Miiller, 3 
 Bloch, 4 and Goze. 6 On this hypothesis, the intestinal worms must 
 have originated in the way just indicated; they must have been 
 innate, or at least have been received by direct transference (for 
 instance by kissing or being suckled). Otherwise, a subsequent 
 
 1 New nord. Beitrage, Bd. L, p. 43, Bd. ii., p. 80. 
 3 " Opere fisico med.. !) t. i., 1733. 
 
 3 Naturforscher, Bd. xiv., 195, 1780. Neues Hamburger Magazin, Bd. xx., 1784. 
 
 4 " Abhandlung von der Erzeugung der Eingeweidewurmer : " Berlin, p. 37, 1782. 
 6 " Versucheiner Naturgeschichte der Eingeweidewurmer: " Blankenburg, p. 4, &c. 
 
 1782. 
 
THEORY OF INHERITANCE. 27 
 
 migration was disproved. The eggs which are extruded with the 
 faeces are, as far as the intestinal worm is concerned, lost, though 
 they may serve as food for other animals (Goze). It was certainly 
 astonishing that by far the greater number of eggs should incur this 
 fate, but even this fact was brought into accordance with the theory. 
 It was asserted that the intestinal worms, which could not, like other 
 animals, deposit their eggs in a chosen place, must leave it to chance 
 whether they passed into the blood-vessels or not ; and furthermore, 
 that the probability of such a haphazard transference was far less 
 than that they should be extruded from the body before it could take 
 place (Bloch). 
 
 That this view, under the influence of that theory of evolution 
 which was then dominant, degenerated into wonderful subtleties and 
 refinements in many of its supporters, must not be considered as due to 
 the theory itself ; x but in other respects it shows so many weak 
 points, that it seems hardly necessary to refute it by calling to mind 
 the various worm-epidemics (sheep-cough, liver rot, &c.), or the Ccenurus 
 that almost invariably kills its host, and generally before it arrives at 
 sexual maturity. The influences, however, which led to this opinion 
 are not difficult to understand. On the one hand was the undeniable 
 fact of the sexuality of the Entozoa and their striking fertility ; on the 
 other, the difficulty, apparently even impossibility, of tracing the origin 
 of these animals to the eggs extruded with the fasces. The idea of 
 hereditary transmission seemed to afford a way out of this dilemma, and 
 appeared all the more feasible, seeing that many observers stated that 
 they had found Entozoa not only in the young of animals, but even in 
 the embryo within the body of the mother. "Whether the cases here 
 alleged were reliable or not, 2 is a matter of indifference to us, but it 
 is surprising, and hardly agrees with this theory of inheritance, that 
 these cases were extremely few in number. It was, accordingly, hardly 
 unjustifiable in Pallas to use not only the directly transmitted eggs, 
 but also those evacuated from the body, to explain entoparasitism. 
 He did not succeed, however, in proving his opinions by direct experi- 
 ment, any more than his illustrious contemporary, van Doeveren,* 
 who also endeavoured to explain the distribution of Entozoa by the 
 theory of the transference of similar germs, but we must not forget to 
 pay our acknowledgment to the clear and accurate perceptions of 
 this great naturalist. Entozoa do actually originate, as we now 
 
 1 According to Eberhard's " Neue Apologie des Socrates" (Th. ii., p. 333), the parasites 
 were present as eggs during the age of innocence, but were hatched after the Fall. 
 
 2 For a list of these cases see Bloch, loc. cit., p. 38 ; also Davaine, " Traite des 
 Entozoaires," 2me ed., p. 11 : Paris, 1877. 
 
 3 " Abhandlung von den WUrmern in den Gedarmen des menschlichen Kbrpers," p. 
 106 : Leipzig, 1776. 
 
28 THEORY OF THE ORIGIN OF PARASITES. 
 
 know well, from transmitted germs, and only in consequence of a 
 process of generation, similar to that which exists in the rest of the 
 animal kingdom. 
 
 In spite of the accordance between our present knowledge and 
 the theories of van Doeveren and Pallas, the one is not the direct 
 outcome of the other. The path of science strays now on one side, 
 now on another side of the direct line of truth, and we ought not, 
 therefore, to be surprised that the theory just quoted was pushed 
 out of the way by other theories before it had time to take root. 
 
 With Pallas, Bloch, and Goze began a long list of helmintholo- 
 gists, of whom the most eminent were Eudolphi and Bremser. 
 Thousands of animals were examined for their parasites, and with 
 such success, that the number of the known Entozoa was soon esti- 
 mated at many hundreds. As the material got larger, the science of 
 helminthology became gradually more and more separated from 
 zoology, and treated as a distinct specialty. This distinction had its 
 evil effects. It caused helminthology to become a mere descriptive 
 enumeration, hardly at all concerned with the life-histories and de- 
 velopment of the animals so carefully registered. This one-sided 
 way of looking at parasites was hardly suitable for solving the ques- 
 tions concerning their origin by careful and unprejudiced experiment. 
 That all previous attempts to explain the presence of these remark- 
 able creatures by the theory of their introduction into the body of 
 their host from without were more or less conspicuously faulty was 
 never at any time doubtful, and perhaps least of all at the present 
 moment. Instead of increasing the number of known facts by the 
 empirical method, and getting, where possible, fresh support on which 
 to base some theory, which might, although not completely proved, 
 furnish numerous and weighty arguments for induction, helmin- 
 thologists were content to point out the insufficiency of earlier investi- 
 gations, and return again to the almost forgotten theory of spontaneous 
 generation, 1 which was at any rate a convenient and simple method 
 of cutting the knot. 
 
 Those were the times when the all-powerful " vital force," governed 
 the organism. And it seemed an easy thing for this " vitality :> to 
 organize a mass of mucus, a villus of the intestine, or a fragment of con- 
 nective tissue, perhaps by an intensified abnormal process of develop- 
 ment, into a bladder- worm instead of a simple hydatid. The structure 
 of the Entozoa was regarded as comparatively simple, and it appeared, 
 therefore, that from this point of view no great difficulties stood in 
 
 1 See specially the excellent work of Bremser, ' ' Lebende Warmer im lebenden 
 Menschen," pp. 1-16 : Wien, 1819. 
 
TEACHING OF RUDOLPHI. 29 
 
 the way of such a theory. The microscope had been for some time 
 laid aside as a not very trustworthy agent, and a simple lens, or the 
 naked eye alone, was sufficient to watch the process of spontaneous 
 generation. 1 When this had once taken place, it was supposed that 
 the Entozoa increased by sexual generation, or else to what purpose 
 had they been provided with generative organs ? The significance 
 of this sexual generation had been kept in the background by the 
 prevailing opinion of spontaneous generation. The majority of the 
 eggs were extruded without being further developed, for, if not, the 
 extraordinary fertility of these creatures would entirely fill their host 
 with their progeny. The supporters of this view, from being well- 
 known authorities in their subject, had such weight, that they readily 
 crushed the evidence advanced against their theory by other observers. 
 This misfortune was partly the fault of their opponents, generally men 
 like Brera, 2 who, in spite of all other qualifications, was ignorant of 
 the necessary details of the subject. As long as Kudolphi's teaching 
 was followed, and the theory of vitality was generally accepted, this 
 view just stated of the origin of the Entozoa was the only one that 
 obtained credence; and it appeared to be strengthened by the discovery 
 of a continually increasing number of bladder-worms and encysted 
 Helminths which were entirely destitute of organs of generation, and 
 were unable, therefore, to propagate themselves by the sexual method. 
 Except by a theory of spontaneous generation, the existence of these 
 worms appeared inexplicable. And yet this appearance was decep- 
 tive so much so, that it is by the help of these very sexless worms 
 that we are now able to show the error of Rudolphi's theory. The 
 general acceptance of this erroneous theory was not, however, over- 
 thrown at a single blow. It was necessary to bring forward numerous 
 facts in order to shatter the belief in spontaneous generation, and set 
 a more credible theory in its place ; but these facts would not have 
 been recognised for a long period, had not a change in the direction 
 and method of biological study given a fresh impulse to helmintho- 
 
 The majority of these fundamental facts were discovered by 
 means of the microscope, which v. Baer, Purkinje, Ehrenberg, and 
 others had again used for scientific investigation, whereby the most 
 brilliant results had already been obtained in other regions of zoology. 
 The first discoveries made by the microscope in helminthology had a 
 most important bearing on the origin of the intestinal worms. 
 
 In the year 1831 Mehlis made the remarkable discovery that the 
 
 1 Bremser, loc. cit., p. 65. Rudolphi, " Entozoorum Hist. Nat. , " vol. i. , p. 811, 1808. 
 
 2 " Medicinisch-praktische Vorlesungen liber Eingeweidewiirmer,' p. 47 ft. seq., 1803. 
 
30 THEORY OF THE ORIGIN OF PARASITES. 
 
 eggs of certain Distomidse contained an embryo (Fig. 16) which in 
 shape and ciliation resembled an Infusorian; it was occasionally 
 provided with an eye-speck, and after being hatched swam about like 
 a Infusorian. 1 What a blow was this simple 
 discovery to the earlier theories as to the fate 
 of the eggs of Entozoa. It had certainly been 
 known from the time of Goze that there were a 
 few viviparous Entozoa, but these were in every 
 case thread - worms, whose young so closely 
 resembled the parent form, that they might 
 easily be supposed to attain to their full 
 development without any migration or further 
 change. In the case discovered by Mehlis, 
 FIG. 16. -Ciliated embryo however, the eggs had been laid, and the em- 
 
 rfjkfonostamum capita ^^ entirely uulike their parentj seemed) from 
 
 their eye-specks and coating of cilia, fitted for 
 a free existence. We recall at once the opinions expressed by Leeuwen- 
 hoek and Pallas, and it is quite intelligible that von Nordmann, 
 who first confirmed the observation of Mehlis, remarked that these 
 parasites, instead of originating by spontaneous generation, " always 
 sojourn during their first life-period in water, and subsequently enter 
 the body of some animal, where they lose their eye-specks and 
 become sexually mature." 2 Von Nordmann certainly acknowledges 
 that this sounds " fabulous " in comparison with the generally 
 accepted theory, but, after further reflection, he insisted upon it, since 
 he found in the gut of a Neuropterous larva, three-quarters of a line 
 long, a species of Nematode with a conspicuous red eye, which was 
 found also living independently in water. 
 
 Soon afterwards von Siebold 3 added to these observations the 
 remarkable fact that the ciliated embryo of Monostomum mutdbile 
 (Fig. 17), a parasite of water-birds, sheltered within its body another 
 creature (a " necessary parasite," as it is termed), which so strikingly 
 recalled the " kingsyellow worm " (Eedia), found by Bojanus in pond- 
 snails (Fig. 18), that one might almost believe "that this creature 
 continued to live after the death of its jailor and perhaps grew into a 
 similar form." Unfortunately this idea could not be proved, although 
 its demonstration would have been of the greatest importance. Von 
 Baer had previously shown that these Bedise 4 gave rise, by a develop- 
 
 1 Oken's 7*w, p. 190, 1831. 
 
 2 " Mikrographische Beitrage," Bd. ii., p. 140, Note, 1832. 
 
 3 Archivf. Naturgesch., Jahrg. i., Bd. L, p. 69, 1835. Burdach, " Physiologic," Bd. 
 ii., p. 208 : Leipzig, 1838. 
 
 * Nova Act. Acad. Cces. Leop., t. xiii., p. 627, 1826. 
 
PROOF OF METAMORPHOSIS IN TREMATODES. 
 
 31 
 
 ment of germ-granules in their interior, to a brood of animals which 
 resemble the tailed Treniatodes, but, unlike them, swim about freely 
 
 FIG. 17. Infusorian-like embryos of FIG. 18. Bojanus' "kingsyellow worms" 
 Monostomum mutabile with the (Redise) from the pond-snail, 
 
 "necessary parasite." 
 
 in water (Fig. 20), and had for this reason been included by the older 
 naturalists among the Infusoria (under the name of Cercaria). 
 
 c. 
 
 FIG. 19. Redise. (A) with germs ; (B) with Cercariae in the interior ; (C) free Cercariae. 
 
32 THEORY OF THE ORIGIN OF PARASITES. 
 
 The investigations of von Siebold were not confined to the eggs of 
 Trematodes, but were extended to the eggs of other intestinal worms, 
 and led to the important discovery that in the tape-worms also the egg 
 contained an embyro before it was laid. Here also the embryo was 
 totally different from the parent, a simple spherical mass, dis- 
 tinguished only by the possession of six stylet-shaped hooks (Fig. 20) 
 arranged in pairs at the anterior pole of the body, and capable of being 
 moved like levers. 1 The subsequent changes undergone by this embryo 
 were for some time uncertain, though there was no doubt that they 
 could only pass into the fully formed animal " by a kind of meta- 
 morphosis." 
 
 FIG. 20. Eggs of the tape-worm with six-hooked embryo. 
 
 Whether von Siebold perceived at that time the important bearings 
 of his observations, must be left undecided. In any case, he neglected 
 to follow them up to their legitimate consequences. This was done 
 some years later by Eschricht, 2 who fully discussed the question of 
 the origin of Entozoa for the first time since the days of Bremser, 
 and who had also, in his masterly researches upon Bothriocephalns 
 latm, 3 decidedly opposed the idea of spontaneous generation. In this 
 work Eschricht collected all the facts that had been lately discovered 
 about the metamorphosis of intestinal worms, and endeavoured to 
 support the view that these phenomena were commonly found among 
 the Helminths. He adduced the great development of the generative 
 organs and the fertility of the Entozoa (the number of eggs produced 
 annually by a single Bothriocephalus latus must be reckoned at at least a 
 million, and of a female thread-worm at 64,000,000 ! ) as evidence 
 that did away with the enormous difficulties besetting the theory of a 
 transmission to " suitable localities." Finally, he recalled the fact, first 
 discovered by Abildgaard, 4 and also known to Bremser and Kudolphi, 
 
 1 Burdach, "Physiologie," loc. clt. Previously to von Siebold, Goze had seen these 
 embryos, but his description and figures (" Versuch, &c." tab. xxii., figs. 20-22,) are so 
 insufficient, and for the most part so incorrect, that no conclusions can be drawn from them. 
 
 2 Edln. New Phil. Journal, 1841. 
 
 * Nova Acta Acad. Gees. Leop., t. xix., suppl. 2, 1841. 
 
 * Naturhistorislc Selsk. Skriftcr, Bd. i., p. 53, 1790, ; see the remarks made on p. 24. 
 
ESCHRICHT UPON THE ORIGIN OF INTESTINAL WORMS. 33 
 
 that Bothriocephalus (Schistocephalus) solidus and Ligula only at- 
 tained to full development when they passed from the body-cavity of 
 a fish to the intestine of a water-fowl, and stated that in all proba- 
 bility many other Helminths wander in a similar way from one 
 organ of their host to another. By these and other facts, Eschricht 
 arrived at the conclusion that the life-history of Entozoa must le 
 considered as analogous on the whole to that of the parasitic larvce of 
 ichneumon-flies and lot-flies, but that each instance demands a special 
 explanation, on account of the complexities possibly introduced. In 
 the meantime, however, no details could be given, but in all pro- 
 bability the various asexual parasites so frequently met with 
 encysted in the muscles and connective tissue, such as bladder- 
 worms, Filaria (including Trichina spiralis), and Echinorhynchus the 
 latter being occasionally during the summer found in thousands in 
 the flesh of fishes must be regarded as immature forms, retaining 
 their primitive larval situation. 
 
 We shall find later on that Eschricht had hit upon the truth in 
 pointing out that change of place and of form were the most im- 
 portant facts in the life-history of parasites. But there were none 
 of the necessary details forthcoming to prove his explanation, and 
 it appears, therefore, in spite of his statements and the support 
 which Valentin's 1 observations lent to them, that the majority of 
 helminthologists continued to uphold the old theory of the spontaneous 
 generation of intestinal worms. 2 
 
 But gradually more and more light was thrown upon the obscurity 
 which enveloped the whole subject of parasitic worms. Shortly after 
 the publication of Eschricht's researches appeared Steenstrup's famous 
 work upon the alternation of generations, which rendered intelligible 
 so many facts in the developmental history of the lower animals that 
 had been previously but incompletely appreciated. The discoveries 
 and arguments brought forward by Steenstrup proved conclusively 
 that there are animals whose descendants in the second or third gene- 
 ration return to the original form of the sexual animal, and that 
 numerous intestinal worms belong to this class. 
 
 The proof of alternation of generations was most completely 
 obtained from the Trematodes, 3 and quite simply, for Steenstrup con- 
 nected their life-history with the above-mentioned Cercariae. By 
 discovering that these latter, in spite of their independent origin, were 
 really larval Trematodes, he determined the fate of a large group of 
 
 1 Repertorium /. Anat. u. Physiol., Bd. vi., p. 50, 1841. 
 
 2 Creplin, Art. " Enthelminthologie " in Ersch u. Gruber's "Allgem. Encyclop. 
 d. Wiss.," Leipzig, 1818-1846, Bd. xxxv. 
 
 3 "Ueber den Generationswechsel : " Copenhagen, p. 50, 1842. Translation by 
 Ray Society, London, 1845. 
 
 C 
 
34 THEORY OF THE ORIGIN OF PARASITES. 
 
 parasites. Steenstrup was not content with solving the enigma merely 
 by hypothesis ; he also endeavoured by direct observation to place his 
 FIG. 21. opinions beyond any doubt. He discovered 
 
 that these Cercaria} (Figs. 21 and 22) fre- 
 quently made their way into the body of 
 FIG. 22. water-snails by boring through the muscular 
 wall, and that, after losing their tails, they 
 became encysted, resembling closely small and 
 as yet asexual Trematodes. These facts were 
 certainly not absolutely new, but those few 
 naturalists who had anticipated Steenstrup 
 in the discovery of the encysted condition 
 of Cercariae, erroneously formed the opinion 
 
 FIGS. 21 and 22.-A free that this P roc ess, instead of being the pre- 
 and an encapsuled Cercaria, cursor of a further development, led merely 
 to the death of the parasite. Moreover, Steen- 
 strup himself fell into an error when he supposed that the tailless Cer- 
 caria arrived at complete maturity within the body of the original 
 host ; von Siebold, 1 who shortly after adopted the opinions of the 
 illustrious Dane, rightly compared the development of the Cercaria 
 to that of Bothrioceplialus (Schistocephalus) solidus and Liyula, and 
 believed that its further growth would not take place until the 
 original host was devoured by some other animal. 
 
 The older investigators (von Baer, see p. 30) had already demon- 
 strated the origin of the Cercariae ; but Steenstrup went further than 
 his predecessors in showing the identity of the " kingsyellow worm " 
 and the "living matrix of the Cercarios" with the "necessary 
 parasite" within the body of the embryonic Monostomum, though 
 the resemblance had been previously pointed out by von Siebold. 
 According to Steenstrup, the egg of the Trematode, expelled 
 from the body of its host, gave rise to a free larva, which 
 after a period of independent existence changed again into a parasite 
 (the "generative sac") after casting its skin. This parasite, how- 
 ever, did not at once become a Distomum, but still remained a 
 larval form (the asexual generation or so-called " nurse "), and in it 
 was subsequently developed, asexually from germ-granules, another 
 active larval form, the Cercaria from which the sexual adult then 
 took its rise. 
 
 If it had been known before that the life-history of an animal 
 could be divided into several cycles, this process of development 
 would have been thoroughly understood some years earlier. The 
 
 1 "Bericht uber die Leistungen, &c.," Archivf. Naturgesch., Jahrg. xiv., Bd. ii., p. 
 321, 1848. 
 
STEENSTRUP'S THEORY OF ALTERNATION OF GENERATIONS. 35 
 
 material was to hand, but there was no one capable of using it. In 
 spite of the close similarity between the Cercaria and the Distomum, 
 no one ventured to state that one was the young of the other, since 
 they had been found in the bodies of quite different animals. 
 
 The phenomenon of alternation of generations threw a fresh light 
 upon the well-known "sexless" Entozoa. According to earlier opinions, 
 these were either independent, spontaneously generated organisms, or, 
 as Eschricht thought, immature forms. The theory of alternation of 
 generations rendered it possible that they played the part of an inter- 
 mediate generation, the "nurse." In fact, Steenstrup 1 had no hesi- 
 tation in speaking of many of these forms, especially the bladder- 
 worms, as " nurses." 
 
 What stress was laid upon the migrations of the embryos by 
 Steenstrup is sufficiently shown by his statement, based upon firm 
 conviction, that the Entozoa are generally only parasitic for a longer 
 or shorter period ; and that at other times, perhaps in different stages 
 or generations, they lead an independent existence, or, as it is termed, 
 " have a geographical distribution in nature (e.g., in water) outside the 
 body of a host." 2 This opinion was strikingly confirmed by a new 
 discovery. 
 
 Dujardin 3 frequently discovered on the ground, and especially 
 after a sudden rainfall, masses of a JFilaria-Iike Nematode (Mermis), 
 resembling very closely Gordius aquaticus, which had been known for 
 some time as an inhabitant of water. This appearance (the so-called 
 "worm-rain") could only be explained by supposing that these 
 creatures had left the bodies of insects or snails, upon which they are 
 parasitic, for the purpose of laying their eggs in the damp earth. Von 
 Siebold proved that this explanation was the right one, by finding not 
 merely these Mermithidae in the bodies of insects and insect larvae, 
 and observing them in the act of wandering away ; but also by the 
 discovery that Gordius was also sometimes parasitic. 4 At the time of 
 their migration the Gordiaceae are mature ; but copulation and ovi- 
 position take place subsequently, in water in the case of Gordius, and 
 in damp earth in the case of Mermis. Von Siebold succeeded later 5 
 in tracing the development of the embryo within the egg during the 
 
 1 Loc. cit., p. 111. 2 Loc. cit., p. 116, Note. 
 
 3 Ann. Sci. Nat., t. xviii., p. 129, 1842. (Similar observations have been fre- 
 quently made since the publication of this paper by numerous observers, and among 
 others by myself. ) 
 
 4 Entomolog. Zeitung, p. 77, 1843. Villot has recently stated that the presence of 
 Gordius in insects is an accidental wandering, while he believes that minnows and loaches 
 are its normal hosts. See Archives de Zool. Exper., t. iii., p. 182 et seq., 1874. 
 
 6 Ibid., 1848, p. 290 ; 1850, p. 239, Jahresb. d. schlesischen GeseUsch. fur vaterL 
 Cultur, p, 56 : Breslau, 1851. 
 
36 THEORY OF THE ORIGIN OF PARASITES. 
 
 winter, and proved thai the young larvae hatched in the spring make 
 their way into the interior of young caterpillars, just out of the egg 
 an important addition to our knowledge of the life-history of Entozoa. 
 But before these observations had been brought to a close, von 
 Siebold had already attempted to fashion the theory of the origin of 
 the intestinal worms according to the newer views, which, as we have 
 already seen, were receiving more and more support from the progress 
 of discovery ; and, with this end in view, he published a complete 
 account of all the known facts relating to the development and gene- 
 ration of these animals. 1 This work, as might have been expected 
 from the wide knowledge of the author and the well-deserved reputa- 
 tion he enjoyed as a naturalist, made a great impression, and spread 
 abroad the conviction that the secrets of the phenomena of ento- 
 parasitism were to be sought for in the migrations and transference 
 of parasites, and were not explicable by any hypothesis of spon- 
 taneous generation. This work did not contain much that was abso- 
 lutely new in the department of helminthology ; for even the opinion 
 
 
 
 FIG. 23. The common bladder-worm of the pig, with invaginated head (A), 
 and with extruded head (B). 
 
 as to the tsenioid nature of bladder-worms (Fig. 23) had been some 
 time previously advanced by Dujardin, although it was treated of in 
 detail for the first time in the article by von Siebold, and based upon 
 the striking resemblance (already pointed out by Pallas and Goze) 
 between the head of the bladder-worm of the mouse and that of 
 Tccnia crassicollis of the cat. 2 
 
 Concerning the development of the bladder-worms, von Siebold 
 had, however, peculiar views. He did not agree with Dujardin in 
 regarding them as larval stages or " nurses," but considered them to 
 be pathological formations caused by certain external circumstances, 
 
 1 Art. "Parasiten" in Wagner's " Handworterbuch der Physiologic," Bd. ii., p. 640 : 
 Brunswick, 1843. 
 
 " Hist. Nat. des Helminthes," pp. 544 and 632, 1845. 
 
DISCOVERIES OF VOX SIEBOLD, DUJARDIX, AND VAN BENEDEN. 37 
 
 such as that the germ of the tape-worm had " lost its way " that is, 
 arrived at some place that was not suitable to its requirements. "We 
 shall have to examine this theory of " straying " later on, but for the 
 present it may be remarked that von Siebold believed it to be of very 
 wide application, and to explain the existence of many other sexless 
 worms (even Trichina), which had not come to a full development on 
 account of having strayed into unsuitable localities. 
 
 Later von Siebold made the developmental history of tape-worms 
 the subject of a special memoir, 1 in which he sought to prove, with 
 special reference to Tetrarhynchus, that the tape-worm heads found 
 so abundantly encysted in predatory fish, originated from embryos 
 that had wandered there, and that these developed into the sexual 
 adult by the formation of segments (Figs. 24 and 25), when their 
 host was swallowed by some other carnivorous fish in whose ali- 
 
 FIG. 24. 
 
 FIGS. 24 and 25.Echinobothrlum minimum 
 (after van Beneden), isolated living head and 
 tape-worm. 
 
 FIG. 26. Transformation of the 
 bladder-worm into a tape-worm 
 (Tcenia serrata). 
 
 mentary canal these chains of tape-worm segments were formed. 
 Von Siebold based these arguments upon induction, but their cor- 
 rectness was subsequently certified by a direct proof of the metamor- 
 phosis and migration of these tape- worm heads. 
 
 Contemporaneously with von Siebold, or even earlier, van 
 
 1 Zeltschr.f. wiss. ZooL, Bd. ii., p. 198, 1850. 
 
38 THEORY OF THE ORIGIN OF PARASITES. 
 
 Beneden had investigated the Entozoa of various predatory fish, 
 especially the shark and ray, 1 and made observations at all stages. 
 He frequently found in the stomach of the shark the digested remains 
 of various osseous fish with Tetrarhynchus heads, some of which 
 were still encysted, some free or nearly so, while others had 
 already buried themselves in the intestine of their new host, and 
 budded out a longer or shorter chain of segments. Van Beneden's 
 researches were so extensive, and dealt with so many different forms, 
 that they fully justified the generalisation that the transference of 
 asexual Entozoa takes place by means of the food of their host, which 
 had been, up till the present time, only proved in the case of Liquid 
 and Schistocephalus. It is not, however, our purpose here to enter 
 particularly into van Beneden's statements as to the development of 
 Cestodes ; we shall recur to it in a future chapter, and content our- 
 selves for the present with mentioning that a bladder- worm, according 
 to this celebrated zoologist, is by no means a pathological condition, 
 but is closely allied in structure and development to the head of a 
 Tetrarhynchus. 
 
 The correctness of this opinion was soon verified by a new ex- 
 periment, which showed that bladder-worms, as von Siebold had 
 previously stated was the case in certain forms, after losing the 
 bladder, become developed into true tape-worms in the intestine of a 
 suitable animal (Fig. 26). The history of helminthology does not, 
 perhaps, contain a single other fact that created such a marked sen- 
 sation. It was, however, not merely the proof that bladder-worms, 
 which had for so long a time formed an impregnable fortress for the 
 theory of spontaneous generation, were really the immature stage of 
 tape-worms, that excited so wide an interest, but it was also the cir- 
 cumstance that Kiichenmeister, 2 the discoverer of this fact, did not 
 discover it merely by chance, but by direct experiment, by the method 
 of feeding, which is so easy to control and repeat, and has furnished 
 the same results in other hands. 
 
 The idea of using this method of proving the nature of bladder- 
 worms was suggested by previous discoveries, but it had, notwith- 
 standing, been made use of by no observer. I say no observer, for 
 the attempts of Klenke in this direction 3 have really not the slightest 
 claim to be mentioned. The method has only proved of value in 
 modern times. The meaning of helminthological experiment was 
 
 1 " Les vers Cestoides": Bruxelles, 1850. (Preliminary account in the Comptcs 
 Rendus Acad. Bdg., 1849). 
 
 2 "Ueber die Metamorphose der Finnen in Bandwiirmer," Prager VierteJjahrsschnft, 
 1852. 
 
 3 "Ueber die Contagiositat der Eingeweidewurmer : " Jena, 1844. 
 
KUCHENMEISTER INTRODUCES HELMINTHOLOGICAL EXPERIMENT. 39 
 
 known to the older workers in this department. It has already been 
 mentioned that Abildgaard in this way proved beyond doubt the 
 migration of Schistocephalus solidus from the body-cavity of the fish to 
 the intestine of the water-fowl. Also Pallas, Bloch, and Goze made 
 the attempt to decide certain questions by the introduction of Hel- 
 minths, or their germs, into various animals, without, however, getting 
 any results of great importance. 
 
 Besides the widespread belief in spontaneous generation, which 
 arrested so powerfully the progress of helminthology, the manifest 
 unfruitfulness of the experimental method gradually caused it to drop 
 into oblivion. It was reserved for Kuchenmeister to reintroduce 
 this method, and to show its importance for all time. A new and 
 active vitality was thus breathed into helminthological science, so 
 that observations and discoveries came thick and fast. Hardly a year 
 had elapsed after the first trial of his method before Kuchenmeister 
 announced 1 that he had succeeded in obtaining bladder- worms from 
 the bodies of animals fed with the ripe proglottides, and thus com- 
 pleted the whole cycle of the life-history of Cestodes. 2 
 
 The earliest experiment was made upon a sheep which died before 
 the complete maturity of the bladder- worms, obviously on account of 
 the experiment. Without a thorough knowledge of the development 
 of the bladder- worms, which was the condition of naturalists at that 
 time, the result of the experiment might have been doubted, had not 
 Haubner 3 and Leuckart 4 completely demonstrated that fact, by 
 rearing almost all known bladder-worms, on an extensive scale, in 
 suitable animals. But this experimental method was not confined to 
 bladder-worms and tape-worms ; it was also applied to other Entozoa, 
 and in these cases also the same facts were strikingly shown. 
 
 De Filippi, 5 de la Valette, 6 and Pagenstecher 7 proved, by means 
 
 1 Gunsburg's Zcitschr. f. klin. Med., p. 448, 1853. 
 
 2 I am unable to understand how Kuchenmeister can complain " that German science 
 hardly thanked him for the services that he had rendered " (This passage is reproduced 
 from the first into the second edition of his " Parasiten des Menschen," 1878, Preface) 
 nor yet why he reproaches me with neglecting no opportunity of attacking him in an unfair 
 manner. On the contrary, I feel satisfied that I have always plainly stated what science 
 does owe to him in the way both of discovery and suggestion (see Preface to the first 
 edition of this work, p. iv.). I have also corrected his unfortunately numerous errors, but 
 only in those cases where it could not be avoided. Had I really wished to attack him, 
 there was plenty of material at my disposal, at any rate more than Kuchenmeister in his 
 most recent work has endeavoured to bring up against me. 
 
 8 Gurlfs Magazin fur ges. T flier- HeUkundc, 1854 and 1855. 
 
 4 " Die Blasenbandwurmer u'nd ihre Entwickelung : " Giessen, 1856, p. 38 et seq. 
 
 5 " Mem. pour servir a 1'hist. gene"t. des Trematodes : " Turin, t. i.-iii. 
 
 6 " Symbolse ad Trematodum evolut. Hist. :" Berolini, 1855. 
 
 7 " Trematodenlarven und Trematoden : " Heidelberg, 1857. "Ueber Erziehung 
 von Distomum echinatum durch Futterung," Archiv /. Naturgesch., Bd. i., p. 246, 1857. 
 
40 THEORY OF THE ORIGIN OF PARASITES. 
 
 of experiment, that encysted Distomes grew mature directly after 
 their migration from one host to another, as von Siebold had believed, 
 and that in this way a migration to another host, or another organ, 
 was necessary in the Trematodes, before they could attain to sexual 
 maturity. Although hitherto the various stages of development of 
 the same species had not been experimentally proved, 1 as in the 
 Cestodes, we must regard our knowledge as having been completed 
 by the experimental verification of this fact, and especially by Zeller's 
 beautiful researches into the life-history of the ectoparasitic forms, 
 especially Polystomum, integerrimum of the frog, 2 which have com- 
 pleted our knowledge in another direction. 
 
 The parasitic Nematodes resisted investigation for a very long 
 time. In the year 1863, when the first volume of my work on para- 
 sites appeared, I was only able to mention a single Nematode besides 
 the Gordiaceae just referred to (p. 35), whose developmental history 
 was thoroughly known. This was Trichina spiralis, which VirchowV 
 and my own 4 researches showed to be developed in the intestines of 
 rabbits, swine, and other Mammalia into a sexual form, which had 
 previously escaped attention. The young of this worm are produced 
 viviparously, and wander away from the intestine, becoming finally 
 encysted in the well-known way in the muscles. Since this time, 
 however, our knowledge has been considerably advanced by the 
 observations recorded in the second volume of my manual. We are 
 now acquainted not only with the life-history and migrations of the 
 Acanthocephala, but also of numerous thread-worms belonging to 
 different groups, and can show experimentally that the germs are 
 extruded from the body of the host, and give rise to young, which, 
 at a particular period of their existence, return to the body of their 
 definitive host. Many of my further observations have greatly 
 widened our conceptions of the parasitic mode of life, and have 
 especially placed beyond a doubt the fact that a cliangc of host is by 
 no means a necessity in tlw life-history of all Entozoa. In many 
 Nematodes, as we shall learn in the next chapter, the young stages 
 are passed in an entirely free existence, and often (especially in 
 certain Strongylidae) under conditions similar to those enjoyed by 
 free-living animals. The life-history of the Pentastomida shows, 
 however, that a migration from one host to another is not confined 
 
 1 Even the experiments of Wagner upon Disiomum cyynoides leave a considerable gap 
 in respect of its migration into the body of the frog, " Beitrag zur Entwickelungsgeschichte 
 der Eingeweidewiirmer," p. 29 et seq. : Haarlem, 1857. 
 
 3 Zeitschr. f. vnsa. Zod., Bd. xxii., p. 1, 1872, and Bd. xxvii., p. 238, 1876, 
 
 8 Archivf. pathd. Anat., vol. xviii., p. 330, 1860. 
 
 * Zeitschr. f. rationelle Medlcin, Bd. viii., pp. 259 and 335, 1860. 
 
FURTHER INVESTIGATIONS BY THIS METHOD, AND THEIR RESULTS. 41 
 
 to the Helminths. The development of these animals, which cer- 
 tainly closely resemble the Helminths in their parasitic mode of life, 
 was worked out by myself some years ago ; x I 
 succeeded in rearing the so-called Pentastomum 
 denticulatum in the intestine of the rabbit from 
 the eggs of Pentastomum tcenioides, and traced the 
 development of the young Pentastomum denticulatum 
 into the adult Pentastomum tcenioides by placing the 
 embryo in the nasal cavity of the dog. 
 
 Although these results of experimental helmin- 
 thology appear so important and numerous, there yet 
 remains much to discover. There are always forms, 
 even among the most common of the Helminths, 
 whose origin is unknown. We must admit that 
 there is much in the natural history of parasites 
 that seems problematical and hardly explicable, in 
 accordance with our present experience, but who 
 would dare, in the face of all the results that have 
 been already achieved, to fill the gaps in our know- 
 ledge with the remnants of some antiquated theory ? 
 If Eudolphi and Bremser, and all the other cham- 
 pions of former helminthological theories, were 
 present to-day, they would lower their colours, and p I 
 refuse to renew the old disputes. The theory they 
 fought for is an error that has been dissipated. 
 
 .27. 1 
 denticulatum. 
 
 1 "Ban und Entwickelungsgeschichte der Pentastomen : " Leipzig, 1860. Preliminary 
 account in Zeitschr. f. rationelle Mcdicin, Bd. ii., p. 48, 1857 ; Bd. iv., p. 78, 1858. 
 
CHAPTER IV. 
 LIFE-HISTOKY OF PARASITES. 
 
 ALL that has been hitherto said about the origin, metamorphosis, 
 and migration of parasites demonstrates plainly that the older 
 observers, who denied any remarkable changes in their life-history, 
 were entirely wrong. We now know that parasitism only repre- 
 sents a single phase in the life of an animal, which, in spite of its 
 importance and extent in many cases, always presupposes another 
 stage. In fact, if we only know concerning a certain animal that 
 it is a parasite, we know but little; thoroughly to understand its 
 history, we must follow out all the separate stages and conditions of 
 its existence, and especially the circumstances under which it becomes 
 a parasite. 
 
 However varied and numerous these may be, they are contained 
 within fixed boundaries. There are certain standards, or rather 
 certain types, of parasitic life, under which the individual cases are 
 more or less definitely grouped. The knowledge of these conditions 
 not only renders the individual cases intelligible, but it also enables 
 us to cast a comprehensive glance over the whole field of parasitism, 
 and therefore we may be thoroughly justified in prefacing the detailed 
 study of individual types by a general sketch of their life-history. 
 
 We commence with the period of sexual maturity, since this leads 
 to the beginning of a new life-cycle. Between different parasites 
 there is a striking difference with respect to the sexual maturity ; for, 
 in agreement with what has already been stated concerning parasitism 
 that it is sometimes perpetual, and sometimes only temporary we 
 find some parasites whose period of sexual maturity coincides with the 
 parasitic period, and others that do not attain to sexual maturity until 
 they have commenced to lead a free existence. 
 
 On the whole, however, the last-mentioned class is but small, and 
 contains only the larvae of parasitic insects and the Gordiaceae and 
 Mermithidse, so that it may be confidently asserted as a law, that 
 parasites, and especially the Helminths, attain sexual maturity while 
 in the parasitic stage, and therefore reproduce themselves in the body 
 of their host. A closer examination shows that this fact is entirely in 
 harmony with the conditions of parasitic life. The position of a 
 parasite is economically considered most fortunate ; its expenditure, 
 
SEXUAL MATURITY. 43 
 
 in locomotion and capture of its food, is small, generally less than in 
 free-living animals, and the income, therefore, is large ; there are in 
 fact, without going into any further detail, numerous causes which 
 must be considered as having a most important effect in furthering 
 sexual maturity. The large balance on the side of income explains 
 the great fertility, upon which stress has already been laid, as of 
 extreme importance in the life-history of these animals. 1 
 
 This, however, is merely en passant. Most important is the fact 
 that sexual maturity and generation take place in most parasites 
 during the time of their parasitic life. Copulation is often accom- 
 plished in the lower animals before the female is fully developed, and 
 occasionally before the stage of parasitism commences. This is the 
 case, at least, in the Lernceoe, where coition takes place while the ani- 
 mals are swimming freely in the water, 2 and differ but little from 
 the free-living Copepoda, and also in the chigoe (Pulex or Ehyn- 
 clwprion penetrans, Fig. 28) it being supposed, at least, that only 
 stationary parasitism is to be taken into consideration. It is, moreover, 
 as is well known, only the female that is a stationary parasite. 
 While the male retains the ordinary form and habits of a flea, the 
 female bores her way into the skin of the foot in man, dogs, and other 
 mammals, and becomes, by the enormous development of the ovary, 
 a simple, motionless bladder. It is improbable, however, that there 
 is anything analogous to this in the Helminths. It was thought at 
 one time (Carter), but wrongly, that the Guinea-worm was fertil- 
 ised before it became parasitic ; but, as a matter of fact, this Nema- 
 tode is only found leading an independent existence in its earliest 
 stages, when the sexual organs are totally undeveloped. 3 It is 
 
 1 We may give this instance of remarkable fruitfulness, in addition to that of the 
 Nematodes, to which allusion has already been made (p. 32). In Tcenia, solium, the con- 
 tents of the uterus of each of the segments is about 6 cubic millimetres, and it holds some 
 53,000 eggs, each egg having a diameter of 0'06 mm. ; seeing that a tape-worm produces 
 yearly at least 800 segments, the total number of eggs will be thus some 42,000,000, a 
 number that under favourable circumstances (instances are known of tape-worms budding 
 off five or six fresh segments daily) is even occasionally exceeded. The extent of this 
 fertility may be estimated by the following calculations : The 64,000,000 eggs, which, 
 according to Eschricht, a tape-worm brings forth in the course of a year, represent (each 
 egg being '05 mm. in diameter, and having a specific gravity equal to that of water), a mass 
 of 41,856 mgrm. (1 egg = '0000654 mgrm.). The adult worm itself weighs about 2*4 grm. or 
 3 '4 grm., including the ovarian tube, and produces therefore yearly 174 gr. per cent, of eggs, 
 about thirteen times as much as the queen bee, whose fertility is about 13 gr. per cent. 
 A woman in giving birth to a child is deprived of about 7 per cent, of her weight, so that 
 a thread-worm is as fertile as a woman would be if she brought forth seventy children 
 every day ! 
 
 2 Glaus, " Beobachtungen Uber Lernaeocera, Peniculus, und Lernaea," Schriftcn dcr 
 Gesdlsch. zur Beforderung d. ges. Naturw. zu Marburg, Suppl.-Heft ii., p. 21, 1868. 
 
 3 See Vol. II. 
 
44 
 
 LIFE-HISTORY OF PARASITES. 
 
 also questionable whether in this latter group parasitism is ever con- 
 fined to the female alone, as has been very generally observed to be 
 
 the case in the Lerncece and their 
 allies. The simple fact that these 
 are animals of which only the 
 females 1 are parasitic is of great 
 interest ; this one-sided parasitism 
 has never yet been observed in 
 the male, except in the already 
 quoted case (p. 10, note) of Bonellia. 
 We must take into considera- 
 tion here that only in a few cases 
 is there a smaller expenditure 
 in proportion to the produc- 
 tion of sexual tissue, while for 
 the female, on the contrary, the 
 economic advantages of parasitism 
 are of great importance. All that 
 has been said concerning the coinci- 
 dence of sexual maturity with the 
 parasitic stage may be summed up 
 in the following sentence : In the 
 Female, majority of parasitic animals the 
 eggs are produced, fertilised, and de- 
 posited while they are in the parasitic stage. Although it is usually the 
 case that the eggs are deposited in the host in which the parasite 
 dwells, there are a few exceptions, such as many Tcenice, where the 
 eggs remain in the proglottides and are extruded from the body of 
 their host. 
 
 FIG. 28. Pulcx pcnctrant. 
 b. Male. 
 
 EGGS AND EMBRYOS. 
 
 In general the eggs of parasites are deposited in those places where 
 the parent lives ; thus the Epizoa lay their eggs upon the outer skin ; 
 the intestinal parasites deposit them in the intestine of their host, and 
 so on. In some cases, however, at the time of oviposition, parasites 
 undertake special migrations like free-living animals. There is a 
 human parasitic worm that does so Distomum hcematobium (Fig. 
 29); this worm usually lives in the portal vein, but when sexually 
 mature, as we learn from Bilharz, migrates in pairs, the female being 
 
 1 In the same manner the sucking of blood by the Culicidae is confined to the females. 
 The males possess a suctorial apparatus with which they can take up fluid nourishment, 
 but it is not so strongly developed as to enable them to pierce the skin. See Dimmock 
 on " The Anatomy of the Mouth-Parts of some Diptera," p. 20 : Boston, 1881. R. L. 
 
DEVELOPMENT WITHIN THE EGG. 
 
 45 
 
 contained in a groove on the lower surface of the male, into the veins 
 of the pelvis, where the eggs are deposited in masses. 
 
 With respect to the stage of development 
 which the eggs have attained when they are 
 laid, the differences in various species are 
 considerable ; every stage, from the egg just 
 fertilised to that which contains a fully 
 developed embryo, is represented. According 
 to the length of time which the fertilised egg- 
 passes in the ovarian duct, it is either 
 unchanged, or has commenced to segment, or 
 may even contain a fully developed embryo ; 
 it happens sometimes, e.g., in Trichina spiralis, 
 that the embryos are hatched while in the 
 body of their mother, which thus becomes 
 viviparous instead of oviparous. It is not 
 uncommon to find all these different ways in 
 animals very closely allied, and it follows 
 therefore that the mode of giving birth to its 
 young affords no clue to the systematic 
 position of a parasite. Quite as varied also 
 is the subsequent history of their eggs; in FIG. 29.Distomum ha>- 
 some cases they remain for a long period matobium, male and female, 
 
 , ., , , , , , . ,, the latter in the canalis 
 
 almost until the young are hatched in the gynsecophorus of the former, 
 identical spot where they were deposited; 
 
 while in other cases they are immediately extruded from the body 
 of their host, and undergo their further development at large . The 
 latter is the most usual, and may be taken for granted where circum- 
 stances favour the dispersion of the eggs. There are numerous 
 exceptions in individual instances, especially among the Epizoa, which 
 often deposit their eggs in a more or less elaborate manner upon 
 various processes of the body (lice, for instance, attach their eggs to 
 hairs ; Dadylogyrus, Diplozoon, &c., attach them to the branchiae of 
 their host). When in such cases the ordinary means of attachment 
 are not sufficient, the egg-shell is provided, as in the species just men- 
 tioned, with some special apparatus of attachment in the shape of 
 suckers or tendril-like processes. These structures are as important 
 to the eggs of parasites as the various similar structures already 
 alluded to (p. 6) are for the parasite itself. 
 
 It very commonly happens among intestinal parasites that the 
 eggs are early extruded from the body of the host, since they are 
 continually being pressed onwards by the semi-fluid contents of the 
 intestine ; this is so often the case, that we are not acquainted with a 
 
46 LIFE-HISTORY OF PARASITES. 
 
 single parasite x that undergoes all its life stages without a change 
 of locality. The number of eggs evacuated with the faeces varies 
 of course with the fertility and the number of the parasites, and 
 is sometimes so considerable, that a very superficial microscopic 
 examination is sufficient to show their presence. Moreover, the 
 intestinal parasites are not the only ones whose eggs are evacuated ; 
 the same thing takes place in animals living in other organs the eggs 
 of Distomum hepaticum reach the intestine through the bile duct, and 
 are thus shed from the body. In the same way the eggs of the 
 bronchial parasite of the sheep, Strongylusfilaria, are removed with the 
 tracheal mucus, and the eggs of Pentastomum tcenioides, which lives 
 in the nasal cavity of the dog, leave the body along with the 
 secretion of the Schneiderian membrane ; the eggs of Strongylus gigas 
 and the embryos of Filaria Bancrofti are passed out along with the 
 urine. 2 Nor is it necessary that the parasites should live in organs 
 that are in direct communication with the exterior ; there are instances 
 where such communications are made by some subsequent abnormal 
 process. The eggs and embryos of Distomum hcematdbium break 
 through the wall of the urinary and rectal blood-vessels in which they 
 are originally laid, into the surrounding spaces, where they form 
 abscesses. The same thing is seen in Stephanurus (the " kidney-worm " 
 of the Americans), which lives near the kidneys in swine, and bores 
 its way into the pelvis of the kidney. The embryos of Dracunculus 
 (Filaria Medinensis), which, as is well known, live between the muscles, 
 reach the exterior through an abscess, which is formed as soon as the 
 head of the worm comes into contact with any part of the cutis. 
 
 If we bear these and other similar cases in mind, and also 
 keep in view the fact that by far the greater number of sexual 
 Helminths live in the alimentary canal, it is evident that we are 
 right in considering the widespread occurrence of these migrations 
 to be important in the life-history of parasites. But those other 
 cases, where the eggs remain upon the spot where they were de- 
 posited until the escape of the young, become, on this account, all 
 the more striking and interesting. We have already mentioned 
 that, to attain this latter end, the eggs of the Epizoa are fastened in 
 various ways to the outer skin. There is no need of anything of this 
 kind in the internal organs, where the inaccessibility of the position 
 
 1 In the German text AnguUlula (Rhabditis) stercoralis was here mentioned as an 
 exception, but, as above mentioned (p. 21, footnote), this form has proved to be merely 
 a developmental stage of a parasite already known under the name of AnguUlula 
 intestinalis. R. L. 
 
 2 A proper microscopical examination of the faeces and excreta under such circum- 
 stances generally furnishes a reliable diagnosis. 
 
WORM-NESTS. 47 
 
 is sufficient of itself to ensure the safety of the eggs. In these cases 
 the eggs are usually laid in the tissue in masses, which are often so 
 large that they form conspicuous tubercle-like bodies the so-called 
 " worm-nests " or " worm-knots." Formations of this kind are often met 
 with in the lungs of mammals, especially of sheep, oxen, and rabbits, 
 sometimes in such profusion that inflammation sets in, and soon kills 
 the animal. 1 Actual worm epidemics are sometimes caused in this 
 way. The parasites which lay the eggs belong to the Strongylidse 2 
 (in the sheep, S. filaria ; in the ox, S. micriirus and S. rufescens ; in the 
 rabbit, S. commutatus = Filaria leporis pulmonalis Frohl.) a group of 
 thread-worms which are commonly found in the trachea and air 
 passages of our domestic animals, and also occasionally of man. 3 Some 
 species of Filaria, in like manner, form "worm-knots." Ecker 4 records 
 the discovery in a rook of a tumour as large as a pea, which contained 
 a full-grown Filaria attenuata and a mass of its eggs. Generally, this 
 species is found free in the intestine of its host, or in the loose con- 
 nective tissue, under conditions unfavourable to the accumulation of 
 large masses of eggs. This phenomenon, exceptionally found in 
 Filaria attenuata, is very general in other members of the same 
 genus. Thus, Filaria sanguinolenta of the dog, which in hot countries 
 is found in almost every third individual, occurs on the aorta and the 
 oesophagus in the sexual condition, massed together in great quantities, 
 with eggs in every stage of development. 5 
 
 Nothing of the kind has been hitherto observed in man, with the 
 exception of the egg-masses of Distomwn (Bilharzia) hcematobium, in 
 the veins of the urinary organs, which only continue for a short time. 
 There are some descriptions of worm-knots in the human body, but 
 the evidence is not quite satisfactory. 6 
 
 1 Bugnion ("Sur la pneumonie vermineuse des anim. domest.," Comp. Rend. Soc. 
 Helvet. a Andermatt, 1875), places with these cases the cysts of Ottulanus, described by 
 me (see Vol. II.) in the lung of the cat. He believes, in opposition to my views, that 
 these are not formed by embryos which have lost their way and died, but considers them 
 as did also Henle, who was the first to describe a case of this kind (Allgem. Path., Bd. 
 ii., pp. 789 and 798) as eggs in various stages of development. Since Stirling (" On the 
 Changes produced in the Lung by the Embryos of Ollulanus tricuspis," Quart. Journ. 
 Micr. Sci., N.S., vol. xvii., p. 145, 1877) has confirmed my opinion, I need say no more 
 about Bugnion's views. I may also mention the fact that occasionally Ottulanus causes 
 worm epidemics. 
 
 2 Vol. II. 
 
 3 Diesing described a certain Strongylus lonyevaginatus, from the lungs of a child 
 that had died of pneumonia (see Vol. II. ) which is probably identical with Strongylus 
 paradoxus from the lungs of the pig. 
 
 4 Archivf. Anat. u. PhysioL, p. 501, 1845. 
 
 5 Lewis, " The Pathological Signification of Nematode Haematozoa :" Calcutta, 1 874. 
 
 6 In the case quoted by Gubler (Gaz. md. de Paris, p. 657, 1858, and, in detail, 
 Mem. Soc. Bid., t. v., p. 61, 1859), the bodies thought to be the eggs of Helminths were 
 
48 LIFE-HISTORY OF PARASITES. 
 
 It is, moreover, not without significance that all these cases of 
 "worm-nests" belong to the Nematodes. Seeing that it is an un- 
 doubted fact that there are parasites whose eggs remain, without further 
 development, in the same place where they were deposited, and are not 
 extruded from the body, as is the rule in other cases, the fate of the 
 embryos that arise from such eggs remains to be examined. The most 
 evident supposition is that these embryos grow to maturity in the 
 same spot by the side of their parent, and this is quite true of certain 
 parasites. It is well known, for instance, that the young lice grow to 
 maturity on the spot where they were born, and the investigations of 
 Wagner, Zeller, and myself have shown that this is also 
 the case with the above-mentioned gill-parasites, at 
 least Dactylogyrus, Diplozoon, &c. 
 
 The life-history of such parasites thus becomes 
 extraordinarily simple. One generation follows another 
 without any change being necessary, either to another 
 host or another organ. If there be any migration, it is 
 due to a mere accident. 
 
 So far as we know, it is only Epizoa which have 
 a simple life-history of this kind, though it has been 
 attempted to prove that certain entoparasites, especially 
 thread-worms, reach maturity without a change of 
 locality. This opinion has, however, been shown to 
 be incorrect, even in the case of the maw-worm (Oxyuris 
 vermicularis), which is generally found in vast quantities 
 in the human alimentary canal, and on that account 
 would seem most apt to support such a theory. * 
 
 Neither has the statement of Norman been con- 
 firmed, according to which all the developmental stages 
 FIG. 30. Rhab- of Anguillula (Rlwibditis) stercoralis should be abun- 
 ditis terricolai dantly met with in the viscera of persons suffer- 
 ing from "Cochin-China diarrhoea," This worm is, as above 
 
 in reality Psorosperms (Coccidium, Lt.), which used frequently to be mistaken for eggs 
 (see postea). Virchow described (Archivf. path. Anat., Bd. xviii., p. 523) a genuine case 
 from the liver ; the eggs, however, proved not to be Pentastomum, as Virchow thought, 
 but Ascaris lumbrieoides, from an examination that I made of some specimens that 
 were sent to me, which were previously forgotten. Thus there is one case of the 
 presence of a thread-worm in the bile duct (see Vol. II. ) So, too, with the " worm-nests " 
 of Trichosomum described by von Siebold in the spleen of a shrew-mouse (Archiv f. 
 Naturgesch., Jahrg. xiv., Bd. ii., p. 358, 1858). The bodies of the worm were found 
 twisted together in knots near the eggs. 
 
 1 In support of this statement, which is at variance with the opinions of Kiichen- 
 meister (" Parasiten des Menschen," first ed., p. 229) and Vix ("Ueber Entozoen bei 
 Geisteskranken," Zeitschr. f. Psychiatric, Bd. xvii.), I may quote my own observations de- 
 scribed in Vol. II. of this work, which have also been confirmed by Zenker (Abhandl. 
 der physile. med. Societal zu Erlangen, Hft. 2, p. 20, 1872). 
 
H^EMATOZOA. 49 
 
 mentioned, no true parasite, but the mature state of a heteromorphous 
 species, the so-called Anguilhda intestinalis. The young are born in 
 the intestine of the host, and attain maturity (like Ehabditis} only 
 after abandoning the latter ; they live in the same way as Rliabditis 
 terricola (Fig. 30), and then give rise to a new generation. 1 
 
 It appears, therefore, that the following generalisation may be safely 
 made : There are no intestinal worms, at least among the typical and 
 constant parasites, whose embryos come to maturity near the parent ; 
 or, in other words, there are none which pass their whole life-cycle in 
 one locality* 
 
 If we now turn to the embryos arising from these so-called worm- 
 nests, it seems clear that they by no means reach further develop- 
 ment in the body of their host, but after a longer or shorter period 
 abandon it for a free external life. All the little that we know by 
 direct experiment agrees with this. Ecker discovered in the body- 
 cavity and blood-vessels of his rook numerous small Filaria-like 
 Nematodes, which he considered to be the embryos of Filaria attenu- 
 ata, 3 and he found them in a later stage as small worms measuring about 
 a line, encysted in the mesentery and other places. Vogt has made 
 similar observations ; 4 he discovered in the body-cavity of a frog two 
 large Filarice, more than an inch long, containing numerous embryos ; 
 the latter he also observed circulating in the blood. Lewis has also 
 shown that numerous Hsematozoa are found in dogs afflicted by Filo.ria 
 sanguinolenta, and the same thing was observed by Gruby and 
 Delafond; 5 and later by Leidy and Walch, 6 in cases where Filaria 
 immitis was present in the right heart of the same animal. In the 
 case last mentioned the embryos have no difficulty in getting into 
 the blood, since they inhabit from the first an organ which they 
 could reach otherwise only by means of an active migration. 
 
 1 Leuckart, " Lebensgeschichte der sog. Anguillula stercoralis, u. deren Beziehung zu 
 d. sog. A. intestinalis," Bericht math. phys. 01. Ic. Sacks. Gesettsch. d. Wiss., p. 85, 
 1882. 
 
 2 I use the term "intestinal worms" instead of "Entozoa" advisedly, since among 
 Gregarine parasites there are many which regularly reach maturity near their parents. 
 In other cases, where the germs grow to embryos at large, there is a regular migration, as 
 in intestinal worms, to and from the body of their host. 
 
 3 Heematozoa, arising from Filaria attenuata, are very commonly met with at Leipzig. 
 Of 38 crows which Kahane examined for this parasite at my suggestion, 28 i.e. 80 
 per cent. contained it, and sometimes in such abundance that the smallest drop 
 of blood contained quantities of them. By examining a certain amount of blood, the 
 weight of which had been previously ascertained, it was found that 1 mgrm. of blood con- 
 tained 601 embryos, which means that the whole of the blood, reckoning it at y^th of the 
 whole 360 gr. net weight, would contain about 18,000,000. 
 
 4 Archivf. Anat. und Physiol, p. 189, 1842. 
 
 5 Comptcs Rendus, t. xlvl, p. 1217, 1858. 
 
 6 Monthly Micr. Journ., p. 157, 1873. 
 
 D 
 
50 
 
 LIFE-HISTOKY OF PARASITES. 
 
 The Nematode Haematozoa have lately attracted considerable 
 attention by their discovery in man (Fig. 31), under circumstances 
 
 \B 
 
 FIG. 31. Filar M sanrjuinis Jiomlni (after Lewig). 
 
 where they must have a considerable pathological signification. The 
 Nematode appears to be very widely distributed in the tropics of the 
 new x as well as the old world. The first discoverer of this human 
 Hsematozoon was Lewis of Calcutta, 2 and he regarded it at first as an 
 adult parasite (Filaria sanguinis) ; but subsequently considered it to 
 be the young form of a Filaria-like worm, 3 which, in the sexual state 
 (as F. Bancrofti, Cobb.), is found viviparous in the subcutaneous 
 connective tissue, more especially of the scrotum. 
 
 [The embryos of this worm probably reach the blood through 
 the lymphatic system. According to Hanson's interesting dis- 
 covery they were usually found in blood only at night, and ap- 
 peared to be entirely wanting during the day. At midnight the 
 number of these embryos in the blood attained its maximum. 4 
 Such at least is the case when the patient preserves the usual order 
 of life, but the reverse happens if he sleep by day and wake by 
 night. 5 This proves satisfactorily that the periodical appearance of 
 
 1 Since Magalhaes (0 proyresso medico, Rio de Janeiro, p. 375, 1878,) has discovered 
 in blood the urinary worm of Wucherer, I cannot doubt that the Brazilian form is identical 
 with the Indian parasite. The worm has also been observed in Japan and Australia. 
 
 2 " On a Haematozoon inhabiting Human Blood," Calcutta, 1872. Ed. 2, 1874. 
 
 3 Centralblatt f. d. medicin. Wiss., No. 43, 1877 ; more in detail Lancet, Sept. 1877, 
 p. 453. See also Cobbold, ibid., p. 495, and Vol. II. of this work. 
 
 * Manson, J&urn. Queckett Micr. Club, vol. iv., p. 239, 1881. 
 r> Mackenzie, Lancet, August 27, 1881. 
 
FATE OF ILEMATOZOA. 51 
 
 the worms is to be explained by the state of the host as regards 
 digestion and muscular exertion, as well as on the motion of the 
 lymph due to these. 1 K. L.] 
 
 If these Hrematozoa arrived at complete maturity in their host, 
 one would expect to find, not merely a vast and increasing number of 
 adults, but also all the intermediate stages. But no one has hitherto 
 observed anything of the kind ; the Hsematozoa remain for months, and 
 even years (Gruby and Delafond), in the same developmental stage, and 
 without altering in size. Even in cases where the adult worms exhibit 
 some variation in their stages of development, as Lewis observed in 
 certain parasites of the dog, there is a considerable gap between the 
 youngest of these and the Hsematozoa in the blood. These facts 
 point to the conclusion that the intermediate stage between the 
 Haematozoon and the fully developed parasite is passed outside the 
 body of the host. 
 
 The analogy of Trichina also lends support to this opinion. The 
 young of this Nematode are produced viviparously, and like the 
 embryos of the above-mentioned Filaria, wander about in the body of 
 their host, 2 the only difference and that an important one being 
 that they abandon the blood-vessels and betake themselves to the 
 intermuscular connective tissue. In both instances we have a wander- 
 ing from one part of the body to another, though it differs in kind 
 in the two forms. But in Trichina also the result of this wandering 
 is by no means the direct degeneration into the parasitic condition of 
 the adult ; the embryos, on the contrary, remain within the muscles, 
 and, after developing up to a certain point, become encysted, and 
 remain in this condition (as muscle- Trichinae, Fig. 15) until they are 
 swallowed by a new host, when they recommence their wanderings. 
 
 In Trichina, therefore, and in these Hsematozoa, a change from 
 one host to another is necessary before sexual maturity can be reached. 
 From the observations of Ecker, that the Hsematozoa of the rook 
 encyst themselves in the mesentery of their host, one would be 
 inclined to believe that the life-history of Filaria attenuata is to be 
 regarded exactly in the same light as that of Trichina, and that the 
 transference into a new host is brought about by the encysted form. 
 I myself, however, believe that this is really not the case, and that the 
 encysted worms have nothing to do with the developmental cycle of 
 Filaria attenuata, not merely because in this event they ought to be 
 far more abundant than they actually are, but because the contents of 
 these cysts, in the instances that I personally examined, agreed entirely 
 
 1 Scheube, "Die Filarien-Krankheit," in Volkmann's " Sammlung Klinischer 
 Vortrage," No. 232, Leipzig, 1883. 
 
 3 Leuckart, " Untersuchungen liber Trichina spiralis," Leipzig, 1860. 2d ed., 1865. 
 
52 LIFE-HISTORY OF PARASITES. 
 
 with certain Nematode larvae, which are present in the same situation 
 in other birds, entirely free from Filaria attenuata or any other 
 Haematozoa. 
 
 The Haematozoa, then, after a longer or shorter sojourn in 
 the blood-vessels, would appear to leave the body of their host in some 
 way or other, and continue their life-history under other conditions. 
 This supposition is strongly supported by what has been observed in 
 human Hsematozoa. According to Lewis, these wormsborethrough the 
 capillaries of the kidney and make their way into the renal tubules, 
 and thence to the exterior. [This emigration takes place so rapidly 
 that, after a day has elapsed, in most cases very few worms, some- 
 times not even one, can be found, unless a fresh introduction have taken 
 place. The significance of this migration to the future development of 
 the worm is still unknown. R L] Up to the present, this observa- 
 tion is certainly unique, and nothing similar has been observed in the 
 Haematozoa of other animals, though investigations have been carried 
 on. 1 If future researches throw no fresh light upon the subject, and 
 it is always possible that the emigration is different and more difficult 
 to observe than in man, whose urine contains in abundance not only 
 the Haematozoa, but also a quantity of blood and albumen mingled 
 with them, which renders their presence obvious there always 
 remains the possibility that the Haematozoa continued to live in the 
 blood, without change, until set free by the death of their host, which 
 enables them to undergo further metamorphosis ; and this is rendered 
 more possible by the fact that no one has succeeded in finding the 
 worms that originate from these Haematozoa in any animals where 
 the latter are present, 2 and it is evident that they must at some time 
 or other have been there. 
 
 We have hitherto been considering those embryos only which, 
 after being hatched, remain for some time in the body of their host ; 
 but these are only a small number of examples. The general rule is, 
 that the eggs, as soon as they are laid, are evacuated from the body 
 of their host togetlier with its excreta, and undergo their further develop- 
 ment in various places and under various conditions, as chance directs. 
 
 1 Borrell (Archiv f. pathd. Anat., Bd. Ixv., p. 399, 1876) shows reason to believe that 
 the Haematozoa of the crow leave the body by the bile-duct, but the above-quoted 
 investigations of Kahane prove that no Filarice are present here, or in the cloaca, 
 ureters, or bronchi, except, of course, there has been some mixture of blood. 
 
 2 Gruby and Delafond only found once, in twenty -four dogs infested with Haematozoa, 
 the Filarice from which these originated. According to Ercolani, Filaria mltis is to be 
 found not only in the heart, but also in the connective tissue under the skin, where it 
 might be easily overlooked (Rivolta, "Studi fatti nel gabinetto di Pisa," 1879). 
 Similarly, among the above-mentioned thirty-eight crows, there were only three in which 
 the presence of Filarice could be proved ; of course it is probable that the sexually mature 
 worms may have escaped observation, here and there, on account of their concealed position. 
 
EFFECT OF DESSICATION. 
 
 53 
 
 In many cases, however, the circumstances and environment are by 
 no means favourable. It may be stated generally that some degree 
 of moisture is necessary to ensure further growth. In dry localities, 
 the eggs lose their power of development, not merely for the time, 
 but permanently, while in damp localities and in water they retain 
 this power for a considerable period. In this respect the eggs agree 
 with the full-grown animals, as do also, even to a greater degree, the 
 embryos, which are frequently hatched in the body of the host and 
 then evacuated. 
 
 We cannot, however, make a hard and fast rule, since there are 
 a number of Helminths whose eggs and embryos can withstand com- 
 plete desiccation with impunity : these are chiefly Nematodes, a group 
 which will be considered later on. The Nematoda, in spite of the 
 simplicity of their organization and development, or perhaps rather 
 because of it, display a variation in the conditions under which they 
 live greater than that of any other group of Helminths. Not only 
 are there parasitic, semi-parasitic, and free-living species, but numerous 
 others, that infest plants, in many of which (wheat, rye, teazle, and 
 clover) they give rise to actual diseases. That these parasites are 
 liable to undergo a process of desiccation at regular intervals is hardly 
 surprising, considering the periodicity of the developmental cycles of 
 the plants which serve as their hosts. As an instance may be cited 
 the wheat-grains which are infested by the young of a Nematode. 
 When the seed is sown, the young parasites are brought into condi- 
 tions favourable for their migration and further development. x This 
 capability of withstanding desiccation is not, however, confined to 
 Nematodes parasitic upon plants, but is occasionally found in those 
 species that infest animals. 
 
 FIG. 32. A, Eggs from Ascaris lumbricoictcs, and &, Trichocepfialus dispar ; a, fresh frorri 
 the faeces ; b, after long exposure to the open air. 
 
 To investigate the influence of desiccation upon the capability for 
 development possessed by the eggs of Nematodes, I have made use 
 
 1 See the excellent researches of Davaine on AnguilluLa tritici. , VInstit., 
 or (more in detail) Mem. Soc. Biolog., t. iii., p. 201, 1856. 
 
 330, 1855$ 
 
.54 LIFE-HISTORY OF 1'AUASITES. 
 
 of a simple piece of apparatus consisting of a ring of blotting-paper 
 enclosed between two glass slides. By alternately damping and drying 
 the paper, the eggs could be brought into a moister or drier atmo- 
 sphere. The conclusion to which I have been led by the use of this 
 apparatus is, that the eggs of numerous Nematodes (Fig. 32), especially 
 those with a thick shell (Ascaris lumlricoides, A. megalocephala, A. 
 mystax, and many free-living Rhabditidae), are not merely capable of 
 enduring a complete desiccation lasting for weeks and even months, but 
 also alternations between the moist and dry conditions. Development 
 does not proceed, however, save in a damp environment, but it is 
 sufficient that the air be merely moist ; indeed, it has appeared to me 
 that this is actually more favourable than wetting the eggs themselves 
 with water. In damp earth development advances rapidly, but if the 
 earth be dried, development is at once checked, without, however, de- 
 stroying the vitality of the germs. 1 
 
 The same holds good for the embryos ; by desiccation they are 
 rendered quiescent, but resume their vital functions on being moistened, 
 as has been known for some time with respect to those species with 
 free-living young (e.g., Filar ia Medinensis and Khabditis). But all the 
 experiments are not opposed to the general law that a moist environ- 
 ment is necessary for the further development of the egys of Entozoa. Of 
 course this is not the only necessary condition. The degree of this 
 moisture, the nature of the environment in other respects, its 
 chemical composition and temperature, are factors which are of varied 
 importance in different cases. Unfortunately, our knowledge on 
 these points is defective, but one fact may be stated with confidence, 
 and that is, that the eggs of certain Nematodes, especially those 
 having a thick shell like Ascaris, possess an extraordinary power of 
 resistance, and can remain a long time without injury to the 
 development of the embryo 2 even in spirit, turpentine, chromic acid, 
 and various poisonous liquids, fatal to the fully grown worm (Bischoff, 
 Leuckart, Munk). Sometimes the degree of concentration of the 
 liquid has an effect. Vix found that the eggs of Ascaris were de- 
 stroyed by a solution of soap of 0'5 per cent., while in a solution of 
 1 per cent, they continued to develop. Similarly, as I have experi- 
 mentally demonstrated, by means of small holes, artificially dug in 
 the earth and filled with decomposing faeces and urine, the eggs of 
 Ascaris lumbricoides are gradually destroyed ; they are likewise often 
 destroyed through the foulness of the water which surrounds them. 
 
 1 The statement of Davaine (M4m. Soc. Biolog., t. iv., p. 272, 1862), that the eggs 
 of Ascarides inhabiting terrestrial animals undergo development when dried up, rests 
 upon an error. 
 
 2 This is the oase also with the so-called Psoross}>erni*, which aru the germs of Gregari- 
 noid parasites (Cviridium, Lt.). 
 
CONDITIONS OF DEVELOPMENT. 55 
 
 All that these experiments show is that there is a limit to the power 
 of resistance possessed by the eggs of Nematodes. 
 
 All the cases just cited, however, by no means lead us to infer 
 that power of resistance is not shown by the eggs of other Helminths, 
 though certainly they do not show it to so great an extent as the 
 Nematoda ; but, compared with other animals, unfavourable conditions 
 of environment take a much longer time to destroy the eggs, and 
 this is no doubt owing rather to the simple fact that the shells of the 
 eggs of these parasites are unusually thick, than to any peculiarity in 
 their protoplasm. In this connection it is important to notice that the 
 eggs of Helminths are not only usually provided with a thick firm shell, 
 but frequently possess in addition a simple or more complex accessory 
 covering of some kind, which occasionally gives them a remarkable 
 and characteristic appearance. This additional protective covering, 
 besides serving to increase their power of resistance, often has other 
 functions ; for example, the eggs of Pentastomum tcenioides, which 
 inhabits the nasal cavity of dogs, have a folded outer layer which 
 enables them to adhere to various bodies when they are ejected from 
 the nose of their host. In a similar way the various filamentous or 
 tufted prolongations of the outer egg-shell 
 (Fig. 33), or the coating of albumen which is 
 sometimes to be found (Fig. 32 a) on the egg- 
 shell proper, serve to secure the attachment 
 of the egg to any body with which it comes 
 in contact. The eggs of Tcenia frequently 
 leave the body of their host enclosed in a FIG. 33. Egg of a tape-worm 
 living covering the proglottis- which pos- *<>** 
 sesses a certain capability of locomotion, and therefore aids consider- 
 ably in the dispersion of the contained ova, which are thus rendered 
 more independent of external agents. In spite of all these arrange- 
 ments, thousands of the eggs of Helminths are destroyed by the 
 unsuitableness of the environment; but this is of no importance, 
 considering their immense fertility. . 
 
 Assuming that the eggs attain to favourable conditions, let us now 
 trace out the further course of their development. In the first place 
 it must be remembered that the eggs reach the exterior in very 
 different stages of development ; in many instances (e.g., Acantho- 
 cephala, Tcenice, many Distomidse, &c.) the embryo is already formed ; 
 in others, again, the egg contains merely the original cell. The presence 
 of an embryo, however, is the preliminary condition of any further 
 change. The eggs that, when extruded from the body of their 
 host, are either not at all or only incompletely developed, at once 
 undergo the process of forming the embryo, and the young is hatched, 
 
56 LIFE-HISTORY OF PARASITES. 
 
 This is known to be the case especially in the eggs of Nematodes, 
 which were not only hatched, according to Schubart and Eichter, in 
 small aquaria, but also, as already mentioned, in a damp atmosphere 
 and damp earth with even greater certainty. This has also been 
 proved in the case of the eggs of numerous tape-worms (Bothrioceph- 
 alus) and Trematodes. 
 
 In many, almost in the majority of instances, embryonic develop- 
 ment only progresses during the summer months, and in many species 
 only under the influence of a considerable degree of warmth ; thus 
 the eggs of Ascaris lumbricoides require a temperature of 20 C., 
 those of Trichocephalus 22 '5 C., and those of Oxyuris vermicularis 
 as much as 40 C. The eggs of the latter develop a complete 
 embryo in a few hours, and when the temperature is increased, in a 
 still shorter time, T while the eggs of Ascaris and Trichocephalus, which 
 
 differ from those of Oxyuris in being 
 entirely undeveloped at the time that 
 they are laid, require several weeks ; 
 and when the temperature varies, as 
 it generally does in this country in the 
 summer, several months elapse before 
 the young are hatched. Trichocephalus 
 
 FIG. 34. Eggs of Oxyuris ver- * f 
 
 micuiaris ; a, 6, freshly laid ; c, with rarely completes its development with- 
 developed embryo. j n ^ year . ^scaris lumbricoidcs, in the 
 
 natural course of events, requires three or four months, and Ascaris 
 mystax some three weeks. On the other hand, the young of Dochmius 
 duodenalis (especially in warmer climates) are hatched in a few days. 
 Similar variations are found in Trematodes and Cestodes, the eggs 
 being sometimes hatched in a few days (Triccnophorus), at other times 
 requiring weeks (Ligula) or even months (Bothriocephalus latus, Dis- 
 tomum hepaticum, &c.) for their full development. This, however, only 
 applies to the summer months ; in winter, even in a heated chamber, 
 development goes on slowly and irregularly; in Ascaris mystax, for 
 example, the first traces of cleavage appear only after several months. 
 Besides temperature, other circumstances are of considerable 
 importance. There are individual differences between eggs them- 
 selves ; embryos rarely develop in them simultaneously ; one egg may 
 have hardly commenced to divide, while another contains a fully 
 formed embryo. Numerous eggs also, under conditions favourable in 
 other respects, never develop, but undergo a process of degeneration 
 in which the whole mass becomes granular and semi-transparent, and 
 all the details of its structure vanish. It may be that these eggs 
 
 1 In sunshine Vix saw an active embryo develop in a quarter of an hour in the eggs 
 of Oxyuris. Zcitschr. f. Psychiatric, Bd. xvii., p. 65, 1860. 
 
MIGRATION OF EMBRYOS. 
 
 57 
 
 have never been fertilised, and this view is supported by the fact 
 that the eggs of unfertilised females among the Nematoda de- 
 generate in the same way without any apparent cause. 
 
 In Entozoa that develop in a short space of time (e.g., Dochmius 
 duodenalis), the early stages are usually passed through while the 
 eggs are traversing the alimentary canal of their host. Occasionally 
 the whole process takes place in the body of the host, especially when 
 they remain there for a considerable period. A longer sojourn in a 
 living host may thus be a necessary preliminary to embryonic 
 development. 
 
 Though our knowledge with regard to the germinal activity of the 
 eggs of Entozoa rests at present upon a comparatively small number 
 of experiments and observations, 1 these are so entirely in harmony, 
 that there is no doubt about the general facts. We can therefore 
 state with confidence that the embryos of oviparous forms develop 
 after the eggs are laid, while those of viviparous (or ovo- viviparous) 
 forms are developed previously, in other words the eggs of all 
 parasites at some time or other, either sooner or later, develop an 
 embryo, 1 * provided that they meet with favourable conditions. 
 
 MIGRATION OF THE YOUNG BROOD. 
 
 The embryos of Entozoa by no means exactly resemble their 
 parents. On the contrary, they never do so, even in the Nematodes, 
 
 FIG. 35. Egg of Distomum 
 hepaticum with embryo. 
 
 FIG. 36. Egg of Both- FIG. 37. Egg of 
 
 riocephalus latus with Echinorhynchus giyas with 
 embryo. embryo. 
 
 1 See the observations of von Willemoes-Suhm, Zcitschr. f. wiss. Zool., Bd. xxiii., 
 1873, p. 343, (Bothriocephalm), and p. 337 (Trematoda). 
 
 2 This holds good also for the generative buds of Gregarines the so - called 
 Pseudonavicellae which, earlier or later (in the body of their host or outside it), develop 
 into embryos. 
 
58 LIFE-HISTORY OK PARASITES. 
 
 which are commonly said to go through no metamorphosis, the 
 resemblance of the young to the adult is more apparent than real. 
 In the majority of cases (in the Cestodes, Distomidie, Eckinorliynchus, 
 and Pentastomum} the differences are so great, that there is hardly 
 any point of similarity between the young and the fully formed 
 worm. (Figs. 35, 36, and 37.) 
 
 It is not so much for zoological reasons, to complete our knowledge 
 of the organization of parasites, that these facts are brought forward, 
 as for the reason that the heteromorphism of the embryo is of the 
 greatest importance in their life-histories. Seeing that the structure 
 of an animal is by no means a matter of chance, but depends upon 
 the capacity for certain actions and modes of life, it is not surprising 
 to find that the embryos of Entozoa, which live under different 
 conditions from the adults, are different from them in form; and 
 these peculiarities are all the more important, because the fate of the 
 embryo is intimately connected with the character of its life-history. 
 
 Let us consider the actual results of observation. It appears that 
 the history of the young parasites that have reached the exterior from 
 the body of their host, whether as eggs or developed embryos, may 
 follow one of two directions ; either the young leave the egg and live 
 in a free state for a longer or shorter period, or they remain within 
 the egg until it is taken into the body of a new host, where they are 
 then set free. In the latter case, there is no free-living stage, for it is 
 always the eggs and not the embryos that are found at large. But it 
 may be objected that it is impossible to draw a sharp line between a 
 living individual and a fully developed egg. This is no doubt true ; 
 but it must be remembered that the relations between the embryos 
 and the outer world are quite different while it is still enclosed within 
 the egg-shell, though an embryo just hatched can hardly be said to be 
 at a higher stage of development than a fully formed embryo still 
 within the egg. 
 
 Whether the embryo of a parasite, when fully developed, be free 
 or not, depends in a great measure on the character of the egg-shell. 
 The latter, when thick and strong, imposes an increased resistance to 
 the exit of the embryo, and sometimes renders it quite impossible for 
 it to leave the egg by its own unaided efforts. This is effected very 
 often by the action of the gastric juice of the new host, which dis- 
 solves the shell, or makes it so weak that the embryo can force its 
 way out without special difficulty. My experiments J with the eggs 
 of tape-worms show clearly that the hatching of the embryo is some- 
 times merely a question of the digestive activity of its host. In some 
 
 1 Leuckart, " Blasen warmer," p. 100. 
 
INFLUENCES OF DIGESTIVE JUICES. 59 
 
 cases, corresponding to the chemical and physical qualities of the egg- 
 shell, the solvent power of the digestive juices must vary, in order to 
 set free the enclosed embryo. The differences in the digestive 
 activities of various animals are but slightly understood, and, in fact, 
 are merely known to exist ; but we cannot doubt that they exercise a 
 profound influence upon the presence and distribution of parasites, 
 when we remember that the eggs of the common tape-worm 
 are digested by mammals, but not by frogs. It would appear that, 
 on the whole, the digestive activity of cold-blooded is less than that of 
 warm-blooded animals, since the larvae of flies, wood-lice, millepedes, &c., 
 and the shells of the eggs of tape-worms and of Ascaris lumbricoides are 
 able to pass through the alimentary canal of the former without being 
 digested. Moreover, since, as we have seen, it depends upon the charac- 
 ter of the egg-shell whether the embryo of a parasite be hatched outside 
 the body of its host or not, we are right in assigning to the first group 
 eggs with thin, delicate shells ; and this is especially the case in the 
 Nematodes (Dochmius, Sclerostomum, &c.) But these thin-shelled 
 eggs do not afford so much protection to their contents as those with 
 a stouter shell ; they are not found, therefore, in all species with free 
 embryos, and are always absent in those cases where the time of in- 
 cubation is longer. In these cases the eggs are thick-shelled, but 
 provided at one end with a kind of lid, which yields to pressure from 
 within, and can be raised up by the embryo (Fig. 38). These are found 
 in the Distomidse, Botliriocephalus, and in many 
 ectoparasites, e.y., the louse. But it must not 
 be supposed that the absence of a lid of this 
 kind hinders in every case the exit of the 
 young ; it is quite possible that the embryos 
 are enabled, by the possession of head spines ^ IQ 3g _ E g of 
 or other similar structures, to bore their way rioccphaius, with opercu- 
 through the egg-shell, as do the young of many lum ; the one is em P^ 
 other animals ; and in the case of Gordius, among Entozoa, this 
 has been actually proved. It is also possible that a damp environ- 
 ment may help to soften the shell, and so facilitate the escape of the 
 embryo, as has been observed in many thread-worms. 
 
 Be that, however, as it may, the main fact of interest to us is 
 that there are numerous parasites which lead a free existence whilst 
 young. The majority pass this stage in water, in localities that the 
 egg has reached, in a more or less direct way, before the escape of 
 their embryos. Sometimes they swim about by the help of a covering 
 of cilia (Bothriocephalus, Monostomum, and other Trematodes Figs. 39 
 and 40) or special appendages (fish-lice) ; sometimes they remain at 
 the bottom, and make their way into the mud. Other species, 
 
60 
 
 LIFE-HISTORY OF PARASITES. 
 
 especially Nematodes, live in damp earth instead of water ; and there 
 are other parasites, but only air-breathing insects, that inhabit drier 
 
 FIG. 39. Free embryo of 
 Distomum fiepaticum. 
 
 FIG. 40. Free embryo of liothrio- 
 cephaltu lattu. 
 
 localities. As a well-known example of this, may be adduced the 
 larva of the flea (Fig. 41), which is found in quantities in retired 
 spots in the neighbourhood of mouldering organic 
 matter, such as dusty corners of rooms, and in the 
 straw of hen-houses, &c. The comparison of a flea- 
 larva to the young of Helminths in this particular 
 does not, however, imply that they agree in all 
 respects. The life of a flea-larva is of long dura- 
 tion, and so noteworthy as regards growth and 
 metamorphosis, that it must be considered quite as 
 important as that of the adult With the Entozoa, 
 however, it is quite different, at least with the 
 greater number ; not merely do the young (except 
 in some cases) take no nourishment during the free 
 stage of their existence, but the period itself is of 
 FIG. 41. Larva of short duration, and serves only as a means to 
 further their distribution and migration. Instead 
 of blind chance, which in other cases directs the fate of the germs 
 of parasites, we have to do with a definite and fixed order of events. 
 This free stage of existence, in spite of its short duration, is long 
 enough, under favourable circumstances, for the parasite to make its 
 way into the body of some host. 
 
 In the first edition of this work I was obliged to leave it 
 uncertain whether any parasites existed in which the free stage 
 
RHABDITIS-LIKE EMBRYOS. 61 
 
 was sufficiently prolonged to allow of their taking in nutriment, 
 and so increasing in size. Eegarding the manifold conditions 
 under which the Nematoda lived, T thought it probable that 
 examples of this kind, if they existed at all, would be discovered 
 in this group. This opinion has been justified. My researches into 
 the life-histories of Nematodes, 1 have proved that there are numerous 
 species, especially among the Strongylidae (of human parasites 
 Dochmius duodenalis), which in their young stage resemble in 
 structure and habits the free-living Khabditidae (Figs. 42, 43), and 
 like them go on feeding and growing for a considerable time. They 
 then change their skin, lose the pharyngeal armature so very 
 characteristic of Rhabditis, and enter upon a stage when they cease to 
 take in nourishment and to increase in size, and need to become 
 parasitic. I need hardly recall the life-history of Ascaris nigrovenosa, 
 shortly described above (p. 2 ), which belongs to this type ; but is 
 peculiar, in that the Rhabditis-\\ke form, which elsewhere is merely a 
 young stage, is here developed into a special generation, which, as 
 soon as it is completed, enters again on a parasitic life. 
 
 Among other Helminths (Cestodes, Acanthocephala, Distomidae) 
 there is nothing of the kind known, and it would indeed be impossible 
 in the two first-mentioned examples, inasmuch as the young has no 
 alimentary canal. Where there are free-living stages in these forms, 
 they serve only for an independent migration. Moreover, the Entozoa 
 are by no means the only animals which have a " swarm-period " like 
 this. It has often been observed in many other animals, such as 
 corals, ascidians, and so forth, when the adult is entirely stationary, 
 or possesses but limited powers of locomotion. Among the insects 
 also we know of wandering larvae, as Newport and Fabre have shown 
 in the Meloidae : the larvae of these beetles live in the nests of various 
 species of bees, to which they can only gain access in the young 
 condition, owing to limited powers of movement of the adults. 2 
 
 As soon as the young parasite meets with its proper host, it 
 abandons its previous course of life, and loses those organs which 
 serve only to establish relations with the outer world, such as cilia, 
 locomotor appendages, and organs of sense, when these are present, 
 
 1 For a fuller statement see Vol. II. 
 
 2 The life-history of these young Meloidse is such an interesting example of pilfering, 
 that I cannot help giving an account of it here, especially as it affords many parallels and 
 points of relation to the study of parasitism. The females lay their eggs in early spring at 
 the roots of the Ranunculacese, dandelions, and other plants rich in honey, that are much 
 visited by bees. As soon as the larvae are hatched, they crawl up the stems of these 
 plants and hide themselves in the corolla. When bees visit the flowers the larvae attach 
 themselves to them by their powerful limbs, and are carried to the nest ; here they lose 
 their appendages and change into inactive grubs. 
 
62 
 
 LIFE-HISTORY OF PARASITES. 
 
 and in this way undergoes a metamorphosis which leads sooner or 
 later to its definitive form. At the same time the parasite fixes 
 
 FIG. 43. jRAabfttii-like condition of young stage of 
 
 FIG. 42. Embryo of Phdbditis Dochmiut trigonocephalus; a, at commencement of the 
 terriccta. free life ; b, at the end of the free life. 
 
 itself on to the outer skin of its host, or in some organ easily accessible 
 from the exterior. In this way we know that the larvse of 
 Trematodes attach themselves to the skin or within the respiratory 
 cavities of water-snails. Others bore their way at once into the 
 intestines or body-cavity. To attain this the parasite seeks a soft, 
 slightly resisting part of the body, against which it presses with its 
 anterior extremity, and gradully forces its way in. Considering the 
 small size of the body, and the fact that many of these embryos are 
 provided with special boring apparatus as, for instance, the larvse of 
 JBothriocepJialm, Gordius, and several species of Distomum it is evident 
 that the difficulties to be overcome are not very great, provided that 
 they attack the right host. It is of course only animals witli 
 a delicate outer skin, such as larval Insecta, Crustacea, Mollusca, 
 and so forth, that are attacked in this way by parasites. 
 
 In many cases the process just described has been actually 
 observed, and in other cases it is inferred by placing together the 
 
OBSERVATIONS ON THE MIGRATION OF FREE EMBRYOS. 63 
 
 parasites and their hosts, and by subsequently finding the parasites 
 within the bodies of the latter, which of course had been previously 
 ascertained to be free from parasites. Von Siebold, 1 in the account of 
 his researches into the Mermithidae,and their wandering into the bodies 
 of minute caterpillars, makes the following remarks : " Thirteen larvae 
 of the spindle-tree moth (Hypomeneuta cognatella), which I had 
 previously found by microscopical examination to be free from 
 thread-worms, were placed in a watch-glass, in which was a quantity 
 of damp earth containing active embryos of Mermis. After eighteen 
 hours, I was able to detect these embryos in five of the caterpillars. 
 In a second experiment, I carefully examined thirty-three caterpillars, 
 to see that there were no Nematode larvae in them to start with, and 
 placed them in similar conditions. After the lapse of twenty- four 
 hours, fourteen of them contained embryos of Mermis, six of them 
 contained two worms a piece, two others contained as many as three 
 a piece. I also made use of young caterpillars not more than three 
 lines in length of Pontea crateegi, Liparis chrysorhcea, Gastropacha 
 neustria, which I took out of the webs in which they had hibernated. 
 They were in a similar fashion placed in a watch-glass with damp earth 
 and embryos of Mermis. On the following day I found that ten out 
 of the fourteen contained embryos ; in five there were two larvae, and 
 in one there were no fewer than three." 
 
 Meissner 2 has recorded similar observations upon the embryos of 
 Gordius. The wandering into the bodies of larvae of Ephemera, which 
 Meissner made use of for his experiments, 3 only took place at night, 
 and always through the appendage which served as a point of attach- 
 ment for the young larvae. " All the Ephemerid larvae which were 
 left for the night in a vessel with the Gordius-embYjos were attacked 
 by them ; all the intruders, however, were found in the legs, usually 
 in the neighbourhood of the first joint, but some had penetrated 
 as far as the muscles of the coxa ; some were quiescent, with the head 
 and proboscis retracted, but the majority were actually moving about, 
 and I was able to see them in the act of making their way between 
 the muscle-bundles. This was done in a very peculiar way. The 
 head was thrust forward, and the hooks, being directed outwards, 
 obtained a firm hold of the tissues ; the head and proboscis were then 
 drawn back, to be again thrust forward in the same way. The pro- 
 boscis thus penetrated some distance, and the hole was then enlarged by 
 the head with its circle of hooks. The contractions of the muscles of 
 
 1 Entomol. Zeitung, p. 239, 1860. 
 
 2 Zeitschr. f. wiss. Zool., Bd. vii., p. 132, 1856. 
 
 3 Villot considers that the larvae of Chironomus, and not Ephemera, are the proper 
 hosts of the young Gordius. Archives d. Zool. exptr., t. iii., p. 186, 1874. 
 
64 LIFE-HISTORY OF PARASITES. 
 
 the Ephemera hindered this process to some extent by pushing away 
 the Gordius-larvae, and rendering their attempts ineffectual. I found 
 one specimen in the fat body endeavouring, but without success, to 
 make its way between two huge drops of fat : every time that the larva 
 pushed them asunder, they flowed together again directly. The longer 
 the Ephemerid larvae remained in the infected water, the greater was 
 the number of Gordius-embryos, which penetrated into their bodies ; 
 I found them in all the organs, the legs, palpi, fat body, and 
 especially in the body-cavity, and even in the dorsal vessel, lying some- 
 times close to one of the valves, and moved to and fro by its pulsations. 
 The number of parasites in one larva was sometimes so great (as 
 many as forty) that I am inclined to attribute to this helminthiasis 
 the sudden mortality which took place among the Ephemerce" 
 
 For a considerable time it was believed that the parasitism of these 
 free embryos was always brought about by their own active migration 
 into the body of a host ; of course, it was possible that it might be 
 effected in other ways, but there was no proof of this. At present 
 we know that many larval parasites find their way into the body of a 
 host by means of drinking water. I transferred a quantity of muddy 
 water containing embryos of Dochmius trigonocephahis (Fig. 43, a, b,) 
 to the alimentary canal of a dog, and saw them grow into the 
 parasite after the lapse of a few days. 1 Man is infected in a simi- 
 lar way by Dochmins diwdenalis, and the horse by Sclerostomum 
 equinum. It is probably only the free young stages of Nematodes 
 which select the natural passages in order to become Entozoa ; at any 
 rate they are the only forms that can, by the thickness of their 
 skin, withstand the action of the digestive juice. Meissner, however, 
 and others have shown that this is not a complete protection ; the 
 former observed numerous Gordius-embvyos destroyed by the digestive 
 fluids of Ephemerid larvae, and I have observed the same in Monosto- 
 mum. In a similar fashion the often numerous specimens of Filaria 
 sanguinis, which the mosquito sucks up with the blood of man, shortly 
 perish almost without exception in its alimentary canal. 2 
 
 1 See Vol. II. 
 
 2 From the observations of Manson (Trans. Linn. Soc. Land., pp. 367-8, 1884) there 
 can no longer be any doubt that the few embryos which can pass without danger to 
 themselves through the intestine of the mosquito undergo further development in the 
 body-cavity, in consequence of which they now differ in size and in the structure of the 
 mouth parts from the embryo at an earlier stage. Manson is of opinion that embryos, 
 having thus reached a certain stage in the body-cavity, get into water only on the 
 death of the host, and that they are taken into the human body with the water. This 
 statement still requires demonstration, but even were this proof forthcoming, there would 
 yet remain a possibility that the embryos evacuated with the urine (which probably no 
 more represent a useless production than the eggs of intestinal worms which pass out with 
 the faeces) may be transported to certain small hosts, and by these means human beings 
 may perhaps be infected more commonly than in the way pointed out by Manson. R. L. 
 
PASSIVE MIGRATION. 
 
 65 
 
 A passive migration which occurs only exceptionally in 
 Entozoa with free-living embryos is the rule in those species 
 which have no free young stage. In the latter group the embryos, 
 still enclosed by the egg-shell, reach in some way or other the intestine 
 of their host ; the process of alimentation affords numerous oppor- 
 tunities for this to happen, which may recur after intervals, varying 
 according to the peculiarities of the mode of life. 
 
 Many animals, especially smaller ones, actually use the eggs of 
 Entozoa as food. 1 have myself observed specimens of Gammarus 
 and Asellus aquations feeding upon eggs of Echinorhynchus which I 
 had placed in their aquarium ; others again take in the eggs acciden- 
 tally along with their food, in greater or less numbers, sometimes still 
 protected by the covering of the body of their parent. 
 
 In the latter way grass-feeding ruminants are infected with the 
 eggs of several tape-worms (Tcenia serrata, T. marginata, T. ccenurus, 
 and T. echinococcus), which live in the intestine of dogs. The " pro- 
 glottides " of these worms crawl out of the faeces and deposit their 
 eggs upon grass stalks. I may also mention here Tcenia saginata 
 (mediocanellata) of man, the eggs of which are transferred in the same 
 
 FlG. 44. Proglottides of Tcenia saginata in various conditions of contraction. 
 
 way to the stomach of the ox (Fig. 44) ; the pig generally becomes in- 
 fected with Tcenia solium by feeding directly upon human ordure, and 
 the meal-worm (Tenebrio molitor) devours, along with the excrement 
 of mice, the contained eggs of Spiroptera murina, while the larva of 
 the cockchafer takes in the eggs of Echinorhynchus gigas with the 
 faeces of the pig. Man himself is frequently attacked by parasites in 
 the same way ; and dogs, when licking their master's hand, deposit 
 the eggs of Pentastomum, which are thus easily transferred to the 
 alimentary canal. 
 
 These few examples show how the germs of parasites are taken 
 in with food. In aquatic animals this is even more easily accom- 
 plished. In those that possess circlets of cilia or tentacles, the 
 eggs may be readily swept into the mouth with food ; and higher 
 
66 LIFE-HISTORY OF PARASITES. 
 
 animals, e.g. fishes, may be occasionally deceived, and devour tape- 
 worms under the delusion that they are nutritious food. It is, 
 moreover, evident that the further development of these eggs, when 
 they have reached the body of some animal, is only possible when 
 the conditions are favourable, and when the eggs themselves contain 
 a living embryo. It is not easy to say how long the embryo will 
 retain its vitality ; accidental and even constant conditions bring 
 about the greatest variations in this respect. In the eggs of the 
 common thread-worm (Ascaris) I have seen active embryos even after 
 the lapse of two or three years, 1 as also in the eggs of Echinorhynchus ; 
 whilst, on the contrary, the eggs of tape-worms usually lose their 
 vitality within a few weeks, even when kept damp. 
 
 The eggs first of all, we may suppose, reach, in a living condition, 
 the stomach of their host, where, if the digestive juices be of sufficient 
 strength, the shell is dissolved ; variations in this respect have been 
 already alluded to (p. 58). The embryo, which was hitherto sufficiently 
 protected by its outer cuticle against dissolution, now becomes free, 
 and acquires the possibility of growth and development. 
 
 DEVELOPMENT OF THE GERMS AFTER MIGRATION. 
 
 That the embryos of some Entozoa, directly they are hatched, leave 
 the stomach of their host, and find their way into its intestine, where 
 they arrive at sexual maturity, has been placed beyond doubt. I suc- 
 ceeded in infecting a sheep with Trichocephalus by feeding it with the 
 eggs containing embryos. 2 In a similar fashion, according to Ehlers, 
 hens and other birds are infected with the tracheal parasite Synyamus, 
 and man (according to Zenker and myself) with Oxyuris. Kuchen- 
 meister and Davaine attempted to breed Ascaris lumbricoides from 
 eggs by drinking water containing them, but numerous and careful 
 experiments in this direction by Mosler and myself led invariably to 
 a negative result. 
 
 In some cases (e.g., Dochmius trigonocephalus, as above men- 
 tioned) the free embryos also attain to maturity without change of 
 locality. It is usual, however, for the development of the young 
 parasites, whether hatched in the stomach or outside the body, 
 
 1 Davaine saw embryos alive after four years, and even after five years had elapsed 
 he was able, by heating them, to induce signs of vitality. (Mim. Sec. Bid., t. iv., p. 261, 
 1862.) He also states that he was able to preserve alive for years eggs and embryos of 
 Tcenia solium and Tania serrata. (Ibid., t. iv., p. 273, 1862.) 
 
 2 See Vol. II. The attempt here referred to is the first which has established the 
 continuous development of an intestinal worm. Of course, Davaine and others had, 
 before this, occasionally asserted such a development, but what they adduced was in no 
 way convincing. 
 
WANDERINGS WITHIN THE HOST. 67 
 
 to follow a more complicated path. The young of Trichina, for 
 example, perforate the intestinal wall, and bore their way into 
 the surrounding organs or tissues. The same holds good for many 
 species of Tcenia, Echinorhynchus, and Pentastomum, whose develop- 
 ment I have traced, and numerous thread- worms Spiroptera murina, 
 Ascaris incisa, Sclerostomum equinum, &c. If we recall and com- 
 pare with these facts the additional fact that the larvae of Distomum, 
 Boihriocephalus, &c. bore their way from the exterior into the body 
 of their host, and make their way into certain definite localities, we 
 may state, in a general way, that the embryos of Entozoa which have 
 found their way into the body of some host do not at once become quiescent, 
 but continue their wanderings, and traverse in various directions the 
 tissues and organs of its body. 1 
 
 These wanderings are facilitated by the minute size and often elon- 
 gated needle-shaped body of the parasite, or by the possession of a 
 boring apparatus. It is, in fact, no harder for a Nematode to make its 
 way through the tissues of an animal than for a bird to move through 
 a thick covert, or a dog through a cornfield, and they leave as little 
 trace of their progress, inasmuch as they rather push between than 
 actually tear their way through the tissues. 
 
 The wanderings of parasites in the larger animals are also often 
 assisted by their getting into the blood-vessels, and so being carried 
 into the remotest parts of the body. Many of them even live for a 
 time as Hematozoa, e.g., the embryos of certain Filarice (p. 49). In a 
 few cases the presence of embryos of Tcenia in the blood has been 
 actually observed (Leuckart, Eaum) ; in other cases, it has been sus- 
 pected from the wide and uniform distribution of the parasites in the 
 body of the host. This conclusion is, however, quite a necessary one, 
 for my researches on Trichina have proved that the connective tissues 
 
 1 If such a migration take place into a pregnant female, the young Entozoa may 
 reach the body of the embryos. Ley dig (Mutter's Archiv f. Anat. u. Physiol., p. 227, 1851) 
 observed in the blood of Mustdus Icevis and its foetus the same Filarice. However, this 
 does not seem to occur always, since in the Mammalia the transference of Nematode 
 Haematozoa to the foetus has not been demonstrated (Chaussat). The wandering embryos 
 of Trichina avoid the body of the foetus. On the other hand, I found in a pregnant 
 Lacerta agilis that nearly all the embryos nine out of twelve contained active sexless 
 Nematodes in the pericardial cavity, in the cavities of the brain and spinal cord, and in 
 the amniotic fluid. Most of the embryos harboured two or three parasites, or even four, 
 and in different parts, without showing the least traces of how the worms made their way 
 in. In the organs of the mother I could not find any of the parasites, nor even the 
 sexual worms which had produced them. Rathke, I find, anticipated me in this obser- 
 vation (Archiv f. Naturgesch., Jahrg. iii., Bd. i., p. 335, 1837). The presence of Entozoa 
 in embryos under such circumstances need excite no wonder ; but the older assertions, 
 according to which the embryos occasionally harboured sexually mature Helminths in the 
 intestine and liver, seem most suspicious (Davaine, loc. cit., p. 11). 
 
68 
 
 LIFE-HISTORY OF PARASITES. 
 
 form passages of communication from one part of the body to another, 
 of which the embryos avail themselves. 
 
 Whether these wanderings take place through the blood-channels, 
 through the connective tissue, or perhaps also directly through the 
 tissues of the organs themselves, and whether they commence at one 
 point or another, at the skin or the alimentary canal, one fact is certain, 
 that they do not last long. Sooner or later the embryo loses its activity, 
 and then, if the circumstances be favourable, undergoes, by grwvth and 
 metamorphosis, further development. 
 
 These favourable conditions occur, perhaps, in only one definite 
 organ or host in a mammal, perhaps, or a snail, in the brain or in 
 the liver. Here only is a further development possible. If, as is 
 frequent, chance has brought it about that the young parasite finds 
 its way into some other animal or some other organ, it shortly dies ; 
 but in many cases it leaves behind traces of its presence. For in- 
 stance, in lambs that have been fed with embryos of Tcenia ccenurus, 
 which only attain to development in the brain, many other organs and 
 tissues, such as the muscles, connective tissue, and liver, are found to 
 be filled with minute cysts, which were no doubt at one time occupied 
 by the worms. 
 
 The nature of the further development, of course, varies with the 
 species of parasite and the structure of the embryo, so that increase 
 of size appears to be the only change which can be universally pre- 
 dicated of parasites. Different species vary much in the dimensions 
 which they attain ; some stop short at a few millimetres in length, 
 others only after exceeding three or four decimetres (Ligula). 
 
 B . C. 
 
 A. 
 
 FIG. 45. Entozoa in the second stage of development. A. Cysticercus 
 of Tcenia solium from the pig ; B. Cysticercus of Tcenia cucumerina from 
 the dog-louse ; C. Young form of Spiroptera murina from the meal-worm. 
 
 If the embryos differ from their parents in form, they undergo 
 metamorphosis as well as increase of size. The organs that served 
 
SECONDARY WANDERINGS. 
 
 69 
 
 merely to assist their wanderings are cast off, and replaced by new 
 
 structures, which subserve their altered conditions of life. Asa general 
 
 rule, Entozoa, in this second developmental stage, show a considerable 
 
 likeness to the fully formed ani- 
 
 mals, but differ in various direc- 
 
 tions. The sexual organs, for 
 
 instance, are incompletely de- 
 
 veloped, or even absent, so that 
 
 the organization is, on the whole, 
 
 less differentiated, in accor- 
 
 dance, certainly, with the com- 
 
 paratively simple and uniform 
 
 conditions of life. The embryos 
 
 remain quiescent, and imbedded PlG . 46< _ A piece of liver from the rabbit> 
 
 in the tissue of organs, generally showing passages made by Cysticercus pisi- 
 
 ..-, . , . , , 
 
 within a cyst, which, as we have 
 
 formis. 
 
 " 
 
 seen, is formed by growth of the connective tissue, or secretion 
 
 FIG. 48. Aspidogaster conchicola. a. Embryo ; 
 b. Young animal, not sexually mature (after Aubert). 
 
 FIG. 47. Archigetes Sieboldi. 
 
 by the growing body of the parasite, and feed on the substances 
 immediately surrounding them (Fig. 45). 
 
70 LIFE-HISTORY OF PARASITES. 
 
 Occasionally, however, this state of quiescence is not absolute ; the 
 parasites move from place to place in a slow and gradual fashion, as 
 might have been expected from the size of the parasites and the 
 tissues that surround them. This is known to occur in certain tape- 
 worms 1 (Tocnia c&nurus, T. serrata, T. marginata) whose embryos 
 develop in the brain or liver of mammals. The bladder-worms, 
 which constitute the second developmental stage of the tape- 
 worms, progress, so long as they remain of small size, in a definite 
 direction by a peristaltic action, and form in this way tunnels 
 and passages, which are subsequently invaded by a growth of 
 connective tissue, and present a striking appearance. Sometimes 
 these passages open into the neighbouring cavities of the body, 
 into which the parasites then fall. This is most generally the case 
 with the tape-worms found in the liver of rabbits and ruminants, 
 which find their way into the body-cavity, where they again 
 become encysted. 
 
 The quiescent stage in the life-history of parasites never takes 
 place in the intestine, but may do so in any other organ of the 
 body, and most generally does so in the connective tissue be- 
 tween the muscles and in the parenchyma of the alimentary 
 canal; some sexually mature parasites are also found in these 
 same organs, and hence the question arises, whether they may 
 not be directly developed from the asexual forms, without any 
 further migration. There are two species in which this certainly 
 does occur; one is Archigetes,* an unsegmented tape- worm of the 
 family Caryophyllseidae (Fig. 47), which is a parasite in the body- 
 cavity of many Xaidae. This worm becomes sexual while yet a 
 bladder-worm, which, in other Cestodes, is only an intermediate 
 stage. Another instance is furnished by the genus Aspidoyaster,' 6 
 which inhabits the pericardial cavity of the fresh-water mussel 
 (Fig. 48), and attains sexual maturity without any further change 
 of habitation. 
 
 All these creatures, however, are parasitic upon invertebrates, 
 a fact of which the importance will appear later on. Among the 
 internal parasites of the Vertebrata we do not know of a single 
 analogous example. We may therefore lay down this general law, 
 that the quiescent stage following upon the wandering embryonic stage 
 does not conclude the life-history of the parasite, which needs rather a 
 radical change in its environment, in other words, a second migration. 
 
 1 See Leuckart, ' ' Blasenbandwiinner, " p. 124. 
 
 2 Leuckart, " Archigetes Sieboldi, eine geschlechtsreife Cestodenamme," Zeitschr. f. 
 tciss. Zool., Bd. xxx. (Suppl.), p. 593, 1878. 
 
 3 Aubert, "Ueber das Wassergefasssystem, u. s. w., d. Aspidogaster conchicola," 
 Zeituchr. f. wiss. Zool., Bd. vi., p, 349, 1855. 
 
NECESSITY OF A SECOND MIGRATION. 
 
 71 
 
 CHANGE OF HOST MIGRATION. 
 
 Neglecting for the present parasites that develop directly (Tricho- 
 cephalus, Oxyuris, Doclimius, &c.), and the other two instances just 
 
 FIG. 49. Sporocyst and Redia, with Cercarise in the interior. 
 
 i 
 
 quoted, the second stage of development leads only to a certain point, 
 which is more or less distant from the final stage of sexual maturity. 
 But this stage lasts for a considerable time, even several years in 
 many parasites ; indeed, until a favourable opportunity affords the 
 conditions suitable for further development. If this opportunity do 
 not occur, they remain in the asexual state, and finally perish. 
 
 The progress of recent research has made us acquainted with the 
 fact that these intermediate forms sometimes, of their own accord, seek 
 out a new host, in the body of which they arrive at sexual maturity. 
 This has been proved in the case of some marine tape-worms 
 (Tetrarliynchus), and will perhaps be ultimately shown to be of more 
 frequent occurrence. This migration is often accomplished by a brood 
 produced asexually from the quiescent form of the second develop- 
 mental stage, it being, of course, supposed that this is active, and not, 
 like the heads of bladder-worms, attached to the mother. This is what 
 takes place in the Distomidae and allied forms of Trematodes. The 
 embryos (Fig. 49) are formed in the interior of saccular parasites, pro- 
 vided or unprovided with an alimentary canal (Redire or Sporocysts), 
 
72 LIFE-HISTORY OF PARASITES. 
 
 which thus, in conformity with the law of alternation of generations, 
 give rise asexually to a new generation. In these cases a number 
 of generative cells develop, which become collected together in increas- 
 ing numbers, and grow into parasites which are different from the 
 foregoing generations, 1 and are, in fact, small sexless Distomes. 
 
 In many cases this generation finds its way into the body of a host 
 while yet contained within the Sporocyst (or Redia). In Distomum 
 macrostomum, for example, whose life-history has recently been 
 worked out by Zeller, 2 the Sporocyst (the so-called Leucochloridium 
 paradoxuni), having the appearance and colour of a tailed fly-maggot, 
 is swallowed, together with its living contents, by some insectivorous 
 bird, after having bored its way through the tentacle of the Succinia 
 infested by it. About six days after, the young Distome, freed from 
 the Sporocyst, has attained to sexual maturity, having cast off' the 
 earlier thick larval cuticle. 
 
 Such a direct transference into the definitive host is, however, 
 rare ; it is usual for the youny parasite first to enter the body of another 
 animal. 
 
 For this purpose, the young Distomum is generally provided with 
 a tail, and often with a boring tooth at the anterior extremity. In 
 this stage it was formerly regarded as a distinct 
 animal, and named " Cercaria" These Cercariae 
 (Fig. 50) abandon their host and live free for 
 some time in water ; they then seek out a new 
 host, 8 which may belong to the Mollusca, Insecta, 
 or Crustacea, and bore their way through its outer 
 skin. Von Siebold 4 observed these parasites in the 
 act of making their way into the body of their 
 host, and he thus describes the process : " I had 
 obtained a quantity of Cercaria armata from the 
 common pond-snail (Lymnceus stagnalis), and put 
 FIG. 50. A free Cercaria. them into a watch-glass containing a number of 
 larvae of Ephemeridse and Perlidae. I could observe, by the help 
 of the microscope, that the Cercarise, swimming about in the water by 
 
 1 Moreover, we know of cases, especially during the winter time, in which the genera- 
 ting cells of certain Rediae give rise again to Redise. It is more generally, however, the 
 Sporocysts that, by division or budding, give rise to a ramified structure that pierces the 
 tissues of its host in all directions. 
 
 2 Zeller, Zeitschr. f. wiss. Zoo/., Bd. xxiv., p. 564, 1874. 
 
 8 If there be no such change of hosts, the young Distomum has no tail. Some few 
 possess instead a short process which looks like a sucker, and serves to assist them in 
 creeping about. 
 
 * "Ueber Band- und Blasenw tinner," p. 26, " Handworterbuch d. Physiol.," Bd. ii. 
 p. 669, 1843. 
 
MIGRATION TO THE DEFINITIVE HOST. 73 
 
 means of the tail, approached the insect larvae, and crept all over 
 them in a restless fashion, evidently seeking something. I also 
 noticed that every now and then they remained motionless, and 
 pressed their frontal armature against the body of the larva. In no 
 case, however, were these boring operations continued, until the Cer- 
 caria happened to have lighted upon a soft portion of the integument 
 between the segments of the insect ; then they used their spine with- 
 out ceasing until they had made an aperture in the 
 skin, through which the flexible fore-part of the body 
 could be introduced. This enlarged the opening, and 
 rendered it possible for the whole body, much attenu- 
 ated during the process, to pass through the outer FlG 5^lT^n en _ 
 skin into the perivisceral cavity. The tail of the cysted Cercaria, 
 Cercaria always remained outside, and was no doubt Wlt out tai ' 
 detached by the sides of the aperture closing together after the body 
 of the parasite had passed through. Having selected for these experi- 
 ments young and delicate larvaa, I could still observe the Cercarige 
 inside their body. They invariably remained quiescent, and assumed 
 a spherical shape (Fig. 51), surrounding themselves with a cyst. The 
 frontal spine was detached during this process of encysting, and was 
 generally visible, lying close to the Cercaria, and within the cyst. 
 This spine, therefore, like the tail, is cast off as soon as its purpose is 
 fulfilled." 
 
 The duration of the free life varies with the species. In our 
 common Cercarise it is generally short, and many species (Distomum 
 hepaticum) do not wait to make their way into the body of some host, 
 but become encysted upon water-plants and other objects. The marine 
 forms, on the other hand, remain longer in the free stage ; some, after 
 entering the bodies of worm-larvae, Copepoda, &c., devour the tissues 
 of their host, and become encysted in its empty shell (Moebius). 
 
 In the quiescent stage the Cercarise are just like other Entozoa in 
 the second developmental period. They await transference to a new 
 host, where, if circumstances favour it, they attain maturity. The 
 changes undergone in the intermediate host in which they some- 
 times remain for years are no more than preparations for the final 
 stage, and consist mainly in a slight increase in size, and the gradual 
 formation of the generative organs. 1 
 
 The change to the last developmental stage is then (even in species 
 
 1 If this intermediate condition be prolonged to an unusual extent, the encysted 
 Distomum often arrives at sexual maturity, as I have noticed myeelf in Ephemerid larvae. 
 Similar cases have been observed by other naturalists, e.g., Linstow and Villot. The last 
 mentioned has published a special paper on this circumstance ( ' ' Observ. de Distomes 
 adultes chez les Insectes," Bullet. Soc. Statistque de VIsZre, t. ii., p. 9, 1868), which, 
 however. I have not seen. 
 
74 
 
 LIFE-HISTORY OF PAKASITES. 
 
 with an intercalated free-living stage) accomplished by a passive trans- 
 ference, a process which we shall have specially to notice when the 
 final fate of an asexual internal parasite comes to be treated of. This 
 transference is, however, by no means always the result of a change of 
 hosts. 
 
 In the mesenteric artery of the horse there is commonly to be found 
 a more or less conspicuous aneurismal swelling. This is caused by 
 
 parasitic Nematodes, belonging to 
 the life - cycle of Sclerostomurn 
 cquinunt (Stronyylus cquinus), 
 which originate from the above- 
 mentioned (p. 61) Ehabditis-likv 
 embryos. The worms live in the 
 fibrous lining of the aneurism (Fig. 
 52), and grow to an inch in length ; 
 they then, after casting their skin, 
 change into the adult condition, 
 which is characterised not merely 
 by the development of the sexual 
 organs, but by the possession of a 
 conspicuous horny mouth-armature 
 with a serrated margin. 1 Ripe 
 sexual products are indeed some- 
 times absent, having been developed 
 directly after the animal has aban- 
 doned its first habitation for the 
 intestinal canal. This wandering, 
 then, as has been pointed out, 
 takes place without the parasite having to leave the body of its 
 host. Subsequently the worm becomes detached from the lining of 
 the aneurism, and is carried by the blood stream into the branches 
 of the arterial system of the intestine, until their decreasing size 
 puts a stop to further progress. Here the parasite begins to bore 
 through the wall of the intestine, which it accomplishes by the trephine- 
 like action of its mouth-cavity, and reaches its ultimate destination. 
 
 But such instances are particularly rare. Whenever we have had 
 the opportunity of observing, under similar circumstances, the trans- 
 ference of an Entozoon to its definitive condition, it is always ac- 
 complished by the worm and its host being devoured by the 
 definitive host. 2 The importance of this for the distribution of 
 
 1 For a detailed account see Vol. II. 
 
 2 Occasionally the reverse is the case, as in certain tape- worms (Ligula, Schisto- 
 ccphcdus), which are often taken up by water-fowls directly from the water (see p. 25). 
 
 FIG. 52. Worm aneurism of the horse. 
 
ACTION OF THE DIGESTIVE JUICES. 
 
 75 
 
 Entozoa we need hardly adduce special cases to prove. The parasites 
 are in this way handed on from one animal to another, from an 
 aquatic to a terrestrial animal, from a cold-blooded to a warm-blooded 
 creature. x The bearer of the encysted parasite falls a prey to some 
 more powerful foe, and is devoured by it : neither herbivorous nor 
 carnivorous animals are secure from the invasion of parasites. The 
 possibility of the transference of parasites increases of course with 
 the number of animals that are devoured, and especially since the 
 bearers of encysted parasites are usually small invertebrates. The 
 larger animals, which need more nourishment, thus take in a gradu- 
 ally increasing number of parasites ; and it is easy, therefore, to 
 understand how it is that of all animals the Vertebrata are most 
 affected by these creatures (see p. 11). 
 
 Only when the parasite has been transferred to the body of its 
 risjht host, and other circumstances are favourable, does it arrive at 
 
 O ' ' 
 
 sexual maturity ; otherwise it rapidly dies. In the same way, the 
 eggs, unless they reach the body of their proper host, die and decay. 
 
 The first change that takes place is the dissolution of the 
 cyst, which, as in the case of the egg-shell, is accomplished 
 by the action of the digestive 
 juices of the stomach ; the 
 parasite then usually makes its 
 way into the intestine. It re- 
 mains for some time exposed 
 to this action of the digestive 
 juices, longer, perhaps, than the 
 embryos hatched from the eggs, 
 which, on account of their small 
 size, can move about more freely, 
 and also, possibly, bore into the 
 walls of the stomach. A longer 
 contact with the digestive juices 
 is but rarely dangerous, since 
 
 they are protected by their large size, and relatively small super- 
 ficies, as well as by the thickness of the cuticle. Sometimes, how- 
 
 
 
 The same thing holds good for the so-called Leucochloridiuiii, and its brood of Distonies 
 (see p. 71). 
 
 1 That temperature has an effect upon Entozoa is shown by the fact that the Dis- 
 tomum of the bat undergoes no further development during the winter sleep of its host, 
 (van Beneden, " Les Parasites des chauves souris," Mtm. Acad. Eelgique, t. xl., p. 23, 
 1873). [In the same way, the Entozoa of cold-blooded animals, when they have not 
 arrived at maturity, stop their metamorphosis during the winter, and produce no eggs, or 
 only very few ; and also, under similar circumstances, Redise, instead of producing Cer- 
 cariae, give rise to new Redise. R. L.] 
 
 FIG. 53. -Bladder- 
 worm with extruded 
 head. 
 
 FIG. 54. Bladder- 
 worm head after di- 
 gestion of the caudal 
 bladder. 
 
76 LIFE-HISTORY OF PARASITES. 
 
 ever, this is not the case, as in the so-called " caudal " bladder of 
 bladder-worms (Figs. 53 and 54), which has a large surface and com- 
 paratively thin walls. This bladder is frequently dissolved, 1 so that 
 the only part which reaches the intestine of the host is the head, 
 which is the most important part of the bladder-worm. There is also 
 no doubt that the varying digestive power of the juices exercises a 
 considerable influence on the fate of these parasites, just as we saw 
 that it did upon the young individuals hatched from the egg in the 
 alimentary tract of their host (p. 59). If the action of the diges- 
 tive juice be not strong enough, as in the case of the frog, which is 
 incapable of dissolving the cysts of Trichina, or if it be too strong, 
 and therefore destroys the parasite as well as its cyst, there is evi- 
 dently an end to the life of the intruder. In these cases the host is 
 not the proper host, for it does not afford conditions suitable for 
 further development. 2 
 
 Besides the action of the digestive juices, there are other im- 
 portant factors to be taken into consideration. In the Trematodes, 
 for instance, at least, in those that perform their migration as free 
 larvae (p. 72), the presence of a capsule is necessary to further 
 development (de la Valette), but not in Tcenia, perhaps because the 
 former, in consequence of their small size and delicate covering, 
 require some protection against the action of the digestive juices 
 of the host. The nutrition required by the parasites themselves is 
 variable in a still higher degree ; but we will return to this point 
 later. 
 
 These processes that I have briefly noticed in the foregoing pages 
 have been proved experimentally step by step. In this way we know 
 that bladder-worms and muscle- Trichina arrive at maturity in the 
 intestine of their proper host, and that the Eckinorhynchus-embYyos of 
 our common Gammarus and Asellus become adult in fish (Echino- 
 rhynchiis proteus) and water-birds (Echinorhynchvs polymorphus}. 
 Thus also the encysted Nematode of the meal-worm (Fig. 45, C.) has 
 been shown to develop in the stomach of the mouse into Spiroptera 
 murina (vel obtusa), and Distomum echinatum of the pond-snail 
 (Paludina) to acquire sexual organs in the bodies of ducks. 
 
 The life-history already quoted (p. 49) of Filaria sanguinolenta 
 renders it probable that the sexually adult parenchyma-worms also 
 
 1 In another place I have experimentally shown that the same alteration takes place 
 outside the body of an animal, " Blasenbandwlirmer," p. 156. 
 
 a The first changes often go on in the " wrong " host, and in experiments by the aid of 
 artificial digestion, as well as in the proper host. The Cysticercus of the pig, for instance, 
 when introduced into the alimentary canal of the dog and rabbit, becomes on the follow- 
 ing day a free tape-worm head, just as if it were in the human alimentary canal ; but it 
 does not develop any further, and soon dies. 
 
PERIODIC PARASITES. 77 
 
 are developed from younger stages that are also internal parasites. 
 Filaria Medinensis has been shown by Fedschenko 1 to make its way 
 into its host as a larva concealed in the body of a Cyclops, which is 
 swallowed along with the water in which it lives. The young worms 
 then reach the intestine, where they remain but a short time, and 
 then bore their way out. The analogy of Filaria sanguinolenta, which 
 is often met with in a larval condition in the so-called "worm- 
 knots/' suggests this, and also the consideration that the difficulties 
 of further internal wandering increase with the growth of the worm. 
 It is no doubt a fact that large, full-grown thread-worms and Tcenicc 
 do bore through the alimentary canal, and even the body-wall of 
 their host ; but this is rare, and when it does occur, the progress of 
 the worms is no doubt assisted by pathological conditions set up in 
 the tissues by their boring. These facts have no special importance 
 in the life-history of parasites, and are rather to be looked upon as 
 accidental, often indeed seriously affecting the life of the host. 
 
 It does not at all follow that every Entozoon that lives outside the 
 alimentary canal must necessarily pass through the latter to reach its 
 desired locality ; Nature has many ways of achieving her ends. An 
 instance of this is afforded by Pentastomum tcenioides, which has a 
 life-history like that of a typical Entozoon. The young form (for- 
 merly described as a distinct species, Pentastomum denticulatum 
 Fig. 56) inhabits cysts in the liver and lung (Fig. 55) of herbivorous 
 mammals ; presently the young animal breaks through its cyst, and 
 makes its way into the body-cavity, after causing considerable injury 
 to the tissues during its transit, and occasionally even causing the 
 death of its host. Sometimes it wanders again into the viscera, 
 most frequently the lymphatic glands. If the body of its host be 
 devoured by a dog or some carnivorous animal, the young Penta- 
 stomum, if not already encysted, finds its way directly through the 
 nostrils (and perhaps also the posterior nares) into the olfactory cavity, 
 where it attains sexual maturity. 
 
 This habit of active migration accounts for the presence of special 
 organs of locomotion, hooks and spines (Fig. 56), which are developed 
 towards the close of the resting stage, and finally laid aside after they 
 have served their purpose. If the young Pentastomum left of its 
 own accord the body of its host, and sought out no fresh host, 
 it would be an example of a periodic parasite attaining sexual 
 maturity while leading a free life. That there are parasites with a 
 life-history of this kind, was briefly stated at the commencement of this 
 chapter ; they are mainly insects, especially flies and wasps. The 
 
 * See Vol. II. 
 
78 
 
 LIFE-HISTORY OF PARASITES. 
 
 Gordiaceae and Mermithidae are instances of this kind of parasitism 
 among the Entozoa, and the migration from the body of their host of 
 
 FIG. 55. Lung of rabbit infected 
 with Pentastomida. 
 
 FIG. 56. Pentastomum denticulalnm. 
 
 proglottides and. other sexual Helminths (e.g., O.w/uris vermicularis) 
 presents an approximation to the same phenomenon. 
 
 The young of these periodic parasites, at least in the case of 
 insects, show certain peculiarities induced by the fact that their 
 migration into the body of a host is accomplished for them by their 
 parents. The latter, possessing as they do the power of free locomo- 
 tion, can evidently influence considerably the fate of their eggs, which 
 is quite as evidently impossible to the Entozoa. Thus the gad-flies lay 
 their eggs on the hair of certain mammals, in situations whence the 
 young can easily in an active or passive manner (e.g., by being licked 
 up) reach their next destination. The Ichneumonidaa make matters 
 easier still for their descendants, by depositing their eggs directly in 
 the perivisceral cavity of caterpillars, for which purpose they are 
 provided with a suitably constructed boring ovipositor. 
 
 The converse of this is illustrated in the Gordiaceae and Mermithidae, 
 whose eggs are laid in water or damp earth, and the young when hatched 
 find their own way by active migration into their proper host, as has 
 already been said. Whether the embryo be conveyed passively or 
 actively, it makes its way into the body of its host, and becomes in 
 
INTERMEDIATE AND DEFINITE HOSTS. 79 
 
 the interior of the infected animal (sometimes even in the intestine, 
 e.g., Gastrus equi) a parasite which may be compared to the second 
 developmental stage of a Helminth. Though there is but rarely an 
 actual encystation (even in the Helminths this condition is sometimes 
 absent), the parasite usually remains quiescent for a time, which it 
 spends in growth and preparation for its future metamorphosis. At 
 the end of this period, it instinctively begins to travel, and leaves its 
 place either by the natura] passages (the gad-fly of the horse, for 
 instance, through the anus, that of the sheep through the nasal 
 cavities), or if this be impossible, by boring through the tissues ; the 
 parasite thus arrives at sexual maturity at large, and often differs 
 markedly in form from the preceding larval stage. 
 
 This wandering often causes the death of the host when it is only 
 a small animal, which is hardly surprising, considering the relative 
 size of the parasite and the injuries it must cause by making its way 
 out. In Gordius the life-history is more complicated, inasmuch as 
 this parasite passes into a second host before commencing its meta- 
 morphosis. There are some facts which show that this is not peculiar 
 to Gordius, and that certain other Nematodes have in all probability a 
 similar life-history. 1 It is evident that, in spite of apparent differ- 
 ences, the parasitism of Gordius is fundamentally similar to the cases 
 already mentioned, and may without any difficulty be classed with 
 them. In both cases there are three life periods, generally distinguished 
 by a difference in form the embryo, the sexually mature adult, and 
 an intermediate stage, which, in view of its outward characters, may 
 be termed a " pupal " stage, if the use of this word will not bring us into 
 a hazardous conflict with the customary terminology when we come 
 to treat of the larvae of parasitic insects. Each of these three stages 
 represents in its biological relations a special department of life. The 
 embryo is destined to commence the parasitism ; it migrates, while the 
 " pupa " resumes the prematurely broken development, and carries it 
 on so far that, after passing to the third stage, sexual maturity appears. 
 The migration, which is the cause of this transitional condition, is 
 usually passive, requires no special advances in structure, and is not 
 effected by any particular developmental conditions. 
 
 This is, of course, merely a rough sketch of the life-history of para- 
 sites, and may be regarded as a generalised description, subject, there- 
 fore, to manifold variations in the way of either greater complexity or 
 greater simplification. Complications arise, for example, by the intro- 
 duction of an intermediate generation with independent migrations. 
 On the other hand, the life-history may be simplified by the inter- 
 
 1 For details see Vol. II. 
 
80 LIFE-HISTORY OF PARASITES. 
 
 mediate stage passing directly, and without migration, into the sexual 
 condition. 
 
 All this, however, is quite exceptional, and the rule for the life- 
 history of parasites may be stated as follows : The life-history of para- 
 sites is divided into two stages (1) the larval, and (2) the sexually mature 
 adult; and each of these is passed in the body of a separate host. Sometimes 
 these two hosts may be merely two individuals of the same species, as 
 in the case of Trichina ; but generally they are quite different, and 
 may belong even to separate orders or classes. Tcenia crassicollis 
 inhabits the liver of the mouse while in the young condition, and the 
 intestine of the cat when adult ; Tcenia maryinata, the connective tissue 
 of sheep and oxen when young, and finally the intestine of wolves and 
 dogs ; the adult Tcenia solium of man is found in the young condition 
 in swine. In a similar way the life of Ligula is divided between fish 
 (Cypriiiidse) and water-birds ; of Echinobothrium typus, between rays 
 and Gammarina ; of Distomum echinatum, between ducks and Paludince; 
 of Amphistomum subclavatum, between the frog and Planorlis ; of Fen- 
 tastomum tcenioides, between the dog and rabbit, and so forth. These 
 examples do not merely prove the justice of the general principle just 
 enunciated, but also bring out prominently the fact that the host of 
 the young parasite is frequently an animal which serves as food for 
 the definitive host ; thus the mouse yields to the cat not only its flesh, 
 but its parasites, and the like happens with the rabbit and dog, the 
 fish and the sea-gull. And this fact is not difficult to understand from 
 a physiological as well as a teleological point of view. If one animal 
 select as its food a certain other animal, it evidently follows that the 
 latter is best suited to its nutritive requirements, hence the conditions 
 of nutrition in both must be somewhat similar, and a parasite capable 
 of living in one would probably also find the other in a great measure 
 favourable to the conditions of its life. This idea, however, must not 
 be pushed too far, since we find, for example, the young of Tcenia 
 crassicollis in many animals which are not preyed upon by cats ; so 
 also the human tape-worm is occasionally found in the asexual 
 state in man himself, a fact which, on the principles just enun- 
 ciated, would seem to justify cannibalism from the stand-point of 
 natural history. The presence of the young stages in Carnivora is 
 certainly to be looked upon in the above light. The Herbivora also 
 often contain parasites which live in the young stage in bodies of 
 other animals; 1 but in these cases, the latter inhabit the same 
 
 1 The statement of Von Siebold (" Handworterbuch d. Physiol.," Bd. ii., p. 647), 
 repeated recently by Ercolani, that the Herbivora become infected with their parasites 
 through the medium of their food, because the parasitic Nematodes of many plants develop 
 in their bodies, has no foundation. The Nematodes of plants are independent species, 
 which are never parasitic upon animals. [On the other hand, the recent researches of 
 
LARGE NUMBERS OF EMBRYOS. 81 
 
 localities, and have been probably swallowed accidentally along with 
 the food. 
 
 Local conditions also are of great importance in the distribution of 
 parasites, as has been shown by Melnikoff and myself, 1 in the case of 
 the dog-louse (Trichodectes), which harbours the young of Tcenia ellip- 
 tica (Fig. 45, B) and passes it into the dog. 
 
 Although the life-histories of parasites largely depend, in the most 
 varied manner, upon the mutual relations of the animals that are 
 their hosts, it is also true that chance plays a very large part in their 
 determination. It is quite by chance, for example, that the egg meets 
 with its proper host, or that its host is subsequently devoured by some 
 other suitable animal. The more complicated, in fact, does the life- 
 history of the parasite become, the greater risk does it run of not 
 being able to complete its life-cycle. Millions of germs perish for 
 one that reaches maturity. 2 We have, however, already spoken of 
 this, and shown how it is compensated by the immense fertility of 
 parasitic worms. " If the eggs and embryos of Helminths always 
 attained to a suitable environment, the bodies of all men would be 
 absolutely full of tape- worms, Nematodes, and other parasites." And 
 it need hardly be pointed out that the lives of the parasites, as well 
 as of their hosts, would be greatly endangered by this. The compli- 
 cated life -history of the parasites serves as a means of checking their 
 too rapid increase, and their metamorphoses and migrations, therefore, 
 are of the highest benefit to them. 
 
 Von Siebold has considered that those Entozoa found in the bodies 
 of the wrong hosts have " lost their way." 3 Nothing can be said 
 against this simple statement, but the conclusions which he has drawn 
 from it are by no means correct. 
 
 In the first place, it must be remembered that any animal which 
 has wandered into a locality where its proper food cannot be obtained 
 a stranded whale, for instance may be said to have " lost its way." 
 The expression ought not to be confined to parasites, although perhaps 
 the occurrence is more general with them. Weinland speaks in the 
 following way of the life-history of corals :* "During the breeding 
 
 Thomas and myself render it very probable that ruminants and other herbivorous mammals^ 
 devour Distomum hepaticum along with plants, to which Cercariae are attached in the*' 
 encysted state. R. L.] 
 
 1 Archivf. Naturgesch. , Jahrg. xxxv., Bd. i., p. 62, 1869. See also Vol. II. 
 
 2 A tape- worm has an average life of two years. It produces in this time some 1500 
 segments (see p. 43, note), each containing 53,000 eggs, the total number of eggs being 
 therefore about 85,000,000 ; since the number of tape-worms remains about the same, one 
 only of these 85,000,000 of eggs reaches maturity. The probability, therefore, against 
 each tape-worm arriving at maturity is as 85,000,000 to 1. 
 
 3 " Handworterbuch. d. Physiol.," Bd. ii., p. 650. 
 
 I 
 
82 LIFE-HISTORY OF PARASITES. 
 
 season of the coral polyps, myriads of microscopic embryos swarm in 
 the neighbourhood of the parent stock ; millions of these are washed 
 out to sea and on to dry land, and perish, or fix themselves in posi- 
 tions where they cannot grow ; but if only a single one find a spot 
 suitable to its growth, Nature has accomplished her purpose, and if 
 this one have reached a spot, perhaps hundreds of miles away, where no 
 corals previously existed, it founds a new colony, which possibly, 
 after the lapse of time, rises as an island out of the sea. These 
 embryos attach themselves to any firm point, but there is no instinct 
 leading them to select a favourable place ; Nature, therefore, produces 
 them in sucli countless numbers, that, on the theory of probability, 
 some are certain to obtain a suitable locality." 1 Who would deny that 
 this is precisely analogous to Helminths "losing their way ?" 
 
 Moreover, von Siebold does not say of those Helminths that they 
 have wandered into the wrong host, but into the body of some animal 
 " not appointed to be their host." But this expression has really no de- 
 finite meaning. If a parasite develop in any given locality, we may 
 conclude that it finds there the necessary conditions of existence ; if it 
 do not develop, we may likewise conclude that the conditions are 
 unfavourable ; but who would undertake to decide whether or no a 
 particular host were " appointed ? " Von Siebold, however, goes still 
 further ; he states that these parasites which have lost their way do 
 not usually die, but continue to grow, " though, on account of the un- 
 favourable environment, they do not thrive, and fail to attain sexual 
 maturity," and in fact "degenerate." 2 Yon Siebold maintained this 
 opinion, 3 even after Ktichenmeister had endeavoured experimentally 
 to contradict it; 4 indeed his words at Konigsberg in 1860 show 
 that he was then still convinced of the accuracy of his opinion : " I 
 cannot understand why the possibility of degeneration in worms is 
 not admitted, since the same thing has been shown to take place in 
 higher animals, as a result of unusual conditions of climate and 
 changed food, and is regarded as a cause of the formation of new 
 species. If in many races an extraordinary growth of hair take place, 
 in some ruminants the horns become larger, the ears of certain domes- 
 tic animals become larger and droop, and in others again a local 
 deposition of fat takes place ; why is it not possible that in many lower 
 animals the influence of varying conditions of the body may give rise 
 to the presence of a serous fluid in certain parts, a local dropsy ? " 8 
 
 1 JaJiresh. d. Ver. voted. Naturkunde Wiirttemberg, Bd. xvi., p. 31, 1860. 
 
 2 Loc. cit. 
 
 3 "Ueber Band- und Blasenwiirmer, u. s. w.," p.65. : Leipzig, 1854. 
 
 4 Prager med. Vierteljnhrschrift, Jahrg. ix., p. 106, 1852 ; "Ueber die Cestoden im 
 Allgemeinen, u. s. w.," p. 12 : Zittau, 1853. 
 
 6 " Konigsberg Naturf. Versamml.," 1860. 
 
DEGENERATION OF ENCYSTED PARASITES. 
 
 83 
 
 These last words show that the author regarded the asexual 
 bladder -worms as Helminths that had degenerated and become drop- 
 sical, in consequence of having lost their way, and got into the body- 
 cavity or muscles of their host instead of its intestine. 
 
 Bladder- worms (Fig. 57) and encysted Trichinae (at that time only 
 known in the encysted condition Fig. 58) were the only parasites 
 regarded thus by von Siebold, and at that period neither the im- 
 portance nor wide distribution of the encysted condition in the life- 
 history of parasites was understood, the generally received opinion being 
 
 FIG. 57. Measly port (natural size). FIG. 58. Trichinosed pork (enlarged 45 times). 
 
 that the germs migrated immediately into the body of their definitive 
 host. At this period, then, von Siebold's hypothesis was an attempt 
 to explain certain striking and unintelligible facts, but has now be- 
 come out of date. It is just these bladder-worms and Trichince that 
 have become by a remarkable concurrence of circumstances the very 
 subject of experimental investigation, and we are now thoroughly 
 acquainted with their natural history. There is not the slightest 
 doubt that what von Siebold considered to be abnormal conditions 
 are in reality the ordinary stages of development ; that Trichina, before 
 arriving at sexual maturity, always passes through a stage in which 
 it is encysted in muscle, and that in the same way tape-worms are 
 invariably derived from bladder-worms. We can, therefore, lay aside 
 von Siebold's theory, which has now hardly any supporters, in spite 
 of the great reputation of its originator. 
 
84 LIFE-HISTORY OF PAKASITKS. 
 
 Our remarks, moreover, are only directed against the practical 
 application of the degeneration theory, and not to an equal extent 
 against its theoretical truth. Degeneration per sc is quite as possible 
 among Helminths as any malformation, which is the result of an 
 
 unusual or insufficient combination of the 
 causes of development. In this way are to 
 be regarded certain varieties in the form of 
 Helminths, as, for example, the so-called 
 Ectiinococcus multilocnlaris or Cysticernis rct- 
 cevwsus 1 (Fig. 59), considered even quite 
 
 FIG. 59. Cysticercu* racemotus recently to be " degenerated " (that is to 
 (after von Siebold). sav> pathologically altered) forms. We are, 
 therefore, in principle brought back to von Siebold's standpoint, or 
 even to that of Pallas (1767) and Hartmann (1685), who were the 
 forerunners of von Siebold in this theory,- but, nevertheless, we cannot 
 agree with the applications of that theory, and the conclusions that 
 were drawn from it. 
 
 This matter, which has been briefly touched upon, leads us 
 naturally to an inquiry into the conditions of development among 
 Helminths, or, in other words, the influence which the environment 
 exercises upon their development. 
 
 An Entozoon, as we know, only develops when its host can fulfil 
 its needs. What happens, then, if it cannot ? It has been already 
 said that a parasite under these circumstances perishes ; but the con- 
 ditions which give rise to this decay, and the time that it takes, are 
 subject to great variations. In the next place, we may mention that 
 the conditions which render development possible are remarkably 
 restricted, so that circumstances of the most varied kind come into 
 play. It is, for example, a well-known fact that the famous Ccenurus 
 only develops in lambs. It has been proved experimentally that the 
 older the lamb becomes the more difficult it is to rear the worms in 
 its body. After feeding the animal with the young parasites, it can 
 be stated with almost mathematical accuracy when it will begin to 
 show the effects of the infection ; while it can be stated with the same 
 probability that an older sheep will Continue in good health though 
 infected with an equal number of parasites. These facts are not 
 peculiar to Coanurus, but common among bladder-worms, though 
 
 1 See for a description of this peculiar form Heller in Ziemssen's ' ' Handb. d. sp. 
 Path. u. Ther.," Bd. iii., p. 334 (Eng. transl., " Cyclop. Pract. Med.," vol. iii., p. 598, 
 London, 1875), and Marchand, Virchaw't Arehivf. pathd. Anat., Bd. Ixxv., p. 104, 1879. 
 Numerous other observations have been made on the frequently irregular forms of the 
 bladder-worm of the brain in man by von Siebold, Krabbe, and others. 
 
 2 See the historical introduction in my " Blasenbandwiirmer," pp. 11-13: Gieasen, 
 1856. 
 
NUTRITIONAL RELATIONS OF HELMINTHS. . 85 
 
 the immunity from their attacks enjoyed by older animals is not 
 perhaps so strikingly shown as in this case. 
 
 Nothing is known of the reason of these phenomena. It is quite 
 uncertain whether it be the nutritive conditions that influence the 
 parasite, or perhaps the greater readiness with which the young tissues 
 yield a path for its wandering. It is not, however, age alone which 
 limits the conditions of this individual development, for we may ob- 
 serve, although rarely, even among old sheep, fresh cases of staggers ; 
 whereas, on the other hand, among lambs we may find single instances 
 of complete immunity from these parasites. Thus, for instance, 
 Baillet mentions the case of a lamb which was fed with mature seg- 
 ments of Tcenia ccenurus nineteen times in the course of about eight 
 weeks, and still no Ccenurus was developed. 1 The experimental 
 helminthologist has often, and even under similar conditions, to 
 register most unexpected results. Thus the author had fed a dog with 
 a multiple-headed Ccenurus, and in about ten days the intestine was 
 filled with more than a hundred completely developed tape- worms ; 
 while in another similar experiment, after three weeks there were 
 found in the intestine of the dog only heads of tape-worms, with 
 bands of segments an inch long attached to them in a few cases only ; 
 and in a third experiment a decidedly negative result was obtained. 
 These three cases are, of course, exceptions, for we may accept it as a 
 rule that the Ccenurus-heads develop completely within three weeks 
 into sexually mature tape-worms. Usually, however, even after this 
 time one may find single immature tape-worms, sometimes even here 
 and there an isolated head ; but these are irregularities which depend 
 rather upon the parasite than upon the host. Analogous cases are 
 also observed in other helminthological experiments. 
 
 Just as old sheep cannot be infected by means of the embryos of 
 Tcenia ccenurus, so in a similar manner muscle- Trichinae develop only 
 rarely in dogs, even though the embryos are found to wander in 
 masses from the intestines into the body-cavity. Similarly Pagen- 
 stecher and I were unable to obtain muscle- Tricliince in birds, although 
 thousands of pregnant animals lived in the intestine. In pigeons 
 the introduced worms never reached sexual maturity. They grew 
 and became similar in appearance to mature animals, but the sexual 
 organs remained without germinal substance (Leuckart). 
 
 From these instances, it is apparent that the conditions of develop- 
 ment of parasites are circumscribed that is to say, besides the " right " 
 
 1 Ann. Sci. Nat., s^r. 4, t. x., p. 190, 1858. In a similar manner Fiedler ("Zur 
 Trichinenlehre," Dcutschcs Archiv fur Idinischc Medicin, Bd. i., p. 68, 1865) reports the 
 case of a man who ate a piece of raw meat, which was strongly infected with Trichinae^ 
 without suffering from it. 
 
86 LIFE-HISTORY OF PARASITES. 
 
 and "wrong" hosts, there are also hosts which only partially satisfy 
 the needs of parasites. In such hosts the invading parasites do not 
 perish immediately after their introduction; on the contrary, they 
 begin to develop as usual, and continue to do so up to a definite point, 
 without, however, completing their development. Whether the worms 
 continue for a longer time in this immature condition, or whether 
 they perish earlier, will apparently depend upon the degree to which 
 the conditions of development influence the life of the parasite. These 
 may vary in individual cases. 
 
 Moreover, the above-mentioned phenomenon may be confirmed by 
 other examples. If a rabbit be fed with the bladder-worms of the 
 common tape- worm of the dog, they not only undergo the usual changes 
 during their sojourn in the stomach (as has been already observed above 
 (p. 75) with regard to the bladder-worms of the pig originating from 
 Tccnia solium), but they also delay for some time in the small in- 
 testine, fastening themselves to the intestinal wall just as in ordinary 
 cases. Some of them even develop a short segmented chain, which 
 differs from the normal beginning of the body of the tape-worm only 
 in that its segmentation is less complete. But here the development 
 stops, until after about ten to twelve days the young worms have all 
 perished (von Siebold, Kiichenmeister). A similar result is obtained 
 by feeding with Tccnia ccenurus. Since the bladder- worm of this tape- 
 worm usually develops only in the brain of lambs, one would expect 
 that the embryo would migrate only thither. But this is not the case, 
 as has been already mentioned (p. 67). The embryos scatter hither 
 and thither from the alimentary apparatus into the diverse organs of 
 the host ; but everywhere, with the exception of the brain, they perish 
 very soon after their entrance. If the infected lamb be examined 
 about three weeks after the feeding, one finds, besides a number of 
 small rounded bladders situated in the brain, which are the first 
 beginnings of the future Ccenurus, also numerous white knots, having 
 the appearance of tubercles, which are situated in the liver and 
 lungs, and more especially between the muscles, and upon closer exa- 
 mination can be recognised as cysts, which have developed round the 
 embryos. Sometimes these cysts may Contain the young of the invad- 
 ing tape-worm small, more or less opaque, and shrunken bladders 
 more rarely they are unchanged and alive, like those in the brain, 
 although for the most part less in size. x In rare cases one of these 
 small bladders may develop in time into a complete Coenurus. 2 
 
 1 See on this head, and on the development of Coenurus in general, Haubner, GurU's 
 llfagazin filr pathol Anat., pp. 248 and 375, 1854. 
 
 3 Thus Eichler found a developed Coenurus under the skin of the sheep, Nathusius 
 under the skin of an ox. Also in the rabbit the Coenurus has been observed in the 
 peripheral organs, but never as yet in the brain. 
 
DURATION OF LIFE AND ULTIMATE FATE. 87 
 
 The causes of these diversities are not yet known to us. We can- 
 not even explain why the liver or the intermuscular connective-tissue 
 has a different influence upon the development of the brood from that 
 of the brain. The supposition that the cause lies in certain differ- 
 ences in the supply and quality of the nutrition cannot of course 
 satisfy us. 
 
 Here and there, however, the space afforded by the different organs, 
 and the peculiarities in the anatomical arrangement of the tissues, 
 may influence the development of the parasites. In this way the 
 bladder- worm in the brain of man grows in the subarachnoid space 
 into sinuous strings, dilated here and there into vesicles, which may 
 reach a length of 25 cm., but only rarely develop a head, so that the 
 true nature of this formation (the above-mentioned Cysticercus race- 
 mosus) has only recently been recognised. Also the so-called " multi- 
 locular " Echinococcus is perhaps only due to the position it occupies in 
 the body; whilst, on the other hand, the sterile Echinococcus (Acepha- 
 locyst) and the hydatid two other forms which can scarcely be con- 
 sidered as normal point to conditions of development which have to 
 be sought in another direction. 
 
 There are only few animals in which the metamorphoses and their 
 individual phases are dependent upon the influence of external factors 
 to such a degree and in such an evident manner as is the case with the 
 Entozoa. The young parasite, if the opportunity of migrating to its 
 definitive host be wanting, remains stationary for life at a stage of its 
 development, which its more fortunate associates, and perhaps even 
 their descendants, have long ago left behind them. 
 
 Moreover, it is not only the periods of migration and development 
 which cause Helminths to be dependent on external circumstances to 
 such an unusual degree. In their later period of existence also their in- 
 dependence is only a limited one. All the different disturbing influences 
 which attack the host, and endanger its health and existence, have 
 more or less an indirect influence upon the indwelling parasite. Some 
 may by certain steps be expelled from the intestine and other internal 
 organs, 1 whilst others may perish through the inflammatory condition 
 of their dwelling. For this reason also it is difficult to determine with 
 certainty the natural length of life of parasites. Concerning some, of 
 course, we know that they continue to live in exposed situations, not- 
 only for several years, but even through a whole decade (BothriocepJialus 
 latus, Tcenia saginata) ; but others again scarcely live longer than a 
 few weeks. On the whole, the period of existence of Entozoa may be 
 assumed to be longer than that of free-living animals of a similar size. 
 
 1 Thread -worms often forsake the intestine on the occurrence of diarrhoaa. 
 
88 LIFE-HISTORY OF PARASITES. 
 
 This is especially true with regard to immature encysted forms, which 
 often live for several decades. With regard to Echinococci and muscle- 
 Trichince, it is well known that in some instances they have lived over 
 twenty years, whilst their corresponding sexual forms perish in a few 
 weeks. 
 
 The changes undergone by those Entozoa that die in their host, 
 and remain there, differ according to circumstances. Some pass 
 through the process of mummification, others that of fatty degenera- 
 tion, and others again calcify. 
 
CHAPTEK V. 
 THE ORIGIN OF PARASITES, 
 
 AND THE GRADUAL DEVELOPMENT OF PARASITIC LIFE. 
 
 IF we endeavour to summarise our knowledge of parasitic life as we 
 have delineated it above, and to express its principal modifications in 
 a few words, we shall arrive at some such scheme as the following : 
 
 I. Temporary Parasitism. To this category belong almost ex- 
 clusively ectoparasites, which differ from their free-living relations in 
 respect only of the quality and source of their nutriment. 
 
 II. Stationary Ectoparasitism. The animals in this group show, 
 on the whole, only slight peculiarities. They either pass through all 
 their developmental stages (from the egg onwards) on the host, or at 
 first lead an independent existence under a form more or less different 
 from the adult. 
 
 III. Entoparasitism. The entoparasite is always stationary, but, 
 with the exception of Rhabditis, which is apparently only occasionally 
 parasitic, never passes through all its developmental stages in one host. 
 The young brood is expelled, either in the form of free embryos or of 
 more or less developed (perhaps wholly undeveloped) eggs. In the 
 latter case the embryonic development occurs in the free state. But 
 from this stage onwards the fate of the embryos varies in different 
 directions. 
 
 (1.) The embryos of Entozoa lead a free life for some time under aii 
 altered form (Nematodes, with Mhabdih's-like young stages). 
 They are not only capable of free motion, but take in food just 
 in the same way as other creatures. 
 
 (a.) In the course of this free life the young form arrives at sexual 
 maturity, and thus only the sexually produced descendants re- 
 turn again to parasitism (Rhabdonema (Ascaris) nigrovenosa). l 
 (b.) The young form itself becomes again a sexually mature parasite 
 at a certain stage of its development. From the commence- 
 ment it enters its definitive host, and its development ends 
 there, although this happens occasionally, as in the case of 
 
 1 Since the name Ascaris is quite incorrect to apply to these animals, I shall adopt 
 henceforth the new generic name Rhabdonema to designate them. 
 
90 THE ORIGIN OF PARASITES 
 
 Scleroetomwm eyu-imiui, in a provisional situation. To the 
 former class, among others, belong certain Strongylidne. 
 (2.) The embryos find, in pursuance of an active or passive migration 
 without ever having led a free life an intermediate host, in 
 the organs of which they develop into a larval form, which then 
 ends its life-history under various circumstances. ' 
 (a.) The larva migrates, and becomes, after complete metamorphosis, 
 a free-living animal (Oestridte among other flies, Ichneu- 
 monidae, Mermithidae, Gordiaceae.) 
 
 (b.) The larva arrives at sexual maturity in its intermediate host 
 without further metamorphosis, as in the above-mentioned 
 Archiyetes and Aspidogaster (p. 69). 
 
 (c.) The larva remains in the intermediate host until it migrates into 
 its definitive host, mostly in a passive way (with food). 
 The developmental history in such cases is extended over 
 two different hosts. This is the form of life-history which 
 we discover in the majority of intestinal worms, and may be 
 considered as really typical among Entozoa (Cestodes, with 
 the exception of Archigetes, Acanthocephala, Distomidae, and 
 Pentastomidae). In individual cases there are here certain 
 modifications, thus 
 
 (a.) The number of intermediate hosts increases, whilst the larva 
 either migrates of itself, and seeks a new host (certain 
 Cestodes), or produces asexually a new generation, which 
 then enters upon a similar change of host (Distomidse). 
 (p.) The intermediate and definitive hosts become one and the 
 same when the embryos do not forsake the latter, but 
 simply wander into its peripheral organs, and there develop 
 into larvae (Trichina). 
 
 (3.) The embryos pass at once, whilst they are yet enclosed by the egg- 
 shell, in a passive manner into the intestine of their definitive 
 host, and here complete their further development. To this 
 class belong numerous Nematodes, especially Trichocephalus 
 and Oxyuris. 
 
 The order in which we have drawn up the various modifications of 
 parasitic life affords us at the same time a picture of the gradual in- 
 crease in development of which this life is capable. The first 
 
 1 The form of entoparasitic life which is here shortly characterised is that which was 
 earliest known to us, and when the first edition of this work appeared, it was the only one 
 known. The existence of the other forms (1 a. and b., and 3) has only been proved later 
 through my researches, especially with regard to Nematodes. (See Vol. II.) To these 
 Helminths, which develop according to the uewly discovered laws, belong the most impor- 
 tant human parasites ; and yet Kuchenmeister (" Parasiten," 2d Ed., Preface) maintains 
 that to the knowledge of parasites "nothing new or of practical importance can be added" 
 beyond what he had asserted ! 
 
FROM FREE-LIVING FORMS. 91 
 
 beginnings are lost, as has been remarked above (p. 1), in the pheno- 
 mena of ordinary life, which latter evidently forms the starting-point 
 of parasitism, or in other words, parasites have, by accommodating 
 themselves to the conditions of a parasitic life, in course of time sprung 
 from creatures originally free. 
 
 The mode of origin which we thus assert for these creatures is in 
 principle precisely the same as that which we also assert, irujonsonance 
 with the doctrine of descent, for the individual free-living forms, when 
 we maintain their development to have been brought about by means 
 of various influences, either directly from one and another, or from a 
 common original form. The manner of adaptation is of course dif- 
 ferent, inasmuch as in the case of free-living animals there is usually 
 a development of faculties which bring about a more extended and 
 complicated capacity, whereas parasites, on the contrary, have a cor- 
 respondingly limited relationship to the outer world, according to 
 the degree of their parasitism. It is only under the influence of ever- 
 changing surroundings, and in the full enjoyment of unembarrassed 
 activity, that an organism can develop itself in every respect and 
 fully form its capacities. Limitation of function is succeeded by 
 stunted growth, and this it is which gives to parasites at least to 
 stationary parasites their peculiar features. The organs and arrange- 
 ments which serve to act upon the outer world, and are excited by it, 
 disappear under the influence of a confined existence ; and by thorough- 
 going parasites this is the case often to such a degree, that the whole 
 organism, which at other times is so artistically formed, degenerates 
 into a simple tube, whose capabilities are almost entirely expended 
 in nutrition and generation. 1 
 
 These influences of parasitic life are especially apparent in those 
 forms, the near relations of which lead a life either completely, or at 
 least to a great extent, free. The classical researches of Johann Miiller 2 
 have made us acquainted with a Mollusc (Entoconclia mirabilis) which, 
 in its young form, possesses the usual attributes of these animals, and 
 does not differ from related young forms any more than the latter do 
 from eacli other ; it lives also, for a time, in the ordinary free state, 
 
 1 This view had already been advocated previously to the rise of the Darwinian theory. 
 In the case of Epizoa by Nitzsch (Magazin der Entomologie, Bd. iii., p. 261, 1818), and for 
 Entozoa by my uncle Fr. S. Leuckart (" Versuch einer naturgemiissen Eintheilung der 
 Helminthen :" Heidelberg, 1827). The latter says (loc. cit. p. 10), "The Helminths show a 
 manifold relationship and likeness to other orders and classes, but at the same time present 
 important differences from the related forms of animals, which, without doubt, have their 
 origin in the entirely different mode of life of the parasitic worms, and in their circum- 
 scribed and completely isolated abode." 
 
 2 J. Miiller, " Ueber Synapta digitata und die Enstehung von Schnecken in Holo- 
 thurien :" Berlin, 1852. 
 
92 THE ORIGIN OF PARASITES. 
 
 but ultimately becomes parasitic, 1 at the same time losing not only 
 its shell which is also the case with certain other snails but also its 
 locomotor, sensory, and alimentary organs, and degenerates into a 
 simple sac filled with sexual products. In the form of this " snail- 
 sac " the parasite is found in the body-cavity of the vermiform Holo- 
 thurian (Synapta digitatct), having its thickened knob-like anterior ex- 
 tremity inserted into the intestinal vessel of its host, so that it may 
 easily be mistaken for a true organ of the latter. No one, without 
 knowledge of the young form, could recognise its Molluscan nature. 
 
 If we regard this retrograde development as a consequence of para- 
 sitism, we do not thereby mean to imply that this exerts its influence 
 from the commencement, and with full force in each individual animal, 
 and that the same process is repeated de novo each time in a similar 
 manner. The influence which the external relations of life exert upon 
 the development of an organism in the present case, as everywhere 
 else, can only have been a gradual one, which must have continued 
 to work for many generations before it could produce such extreme 
 effects. It is not a sudden transformation, but a slow and steady 
 progressive adaptation to the conditions of a parasitic mode of life, 
 of which we see the results in the above-cited organism. We must 
 accept the conclusion that the Mollusc to continue with our example 
 has not exhibited this particular form of parasitism from the com- 
 mencement, but has only gradually adopted the above-described mode 
 of life. 
 
 When the number of parasites in any group of animals is in- 
 creasing, we often see also the various stages of parasitism in exist- 
 ing forms allied to each other. The sum of the degeneration and 
 transformation is then seen to be of different extent in different 
 species, for the transformation of the organism in no case goes further 
 than the circumstances of the parasitic life require. Step by step we 
 can see how, under such circumstances, animals that feed usually on 
 organic detritus, like the Asellidtv, or lead a predatory life like the 
 free-living Copepoda (represented in our waters by the genus Cyclops) * 
 exchange their free life for a parasitic one. Often they are only tem- 
 porary parasites, differing from the most nearly related forms perhaps 
 only in the possession of more powerful hooks, whilst in other cases 
 they continue for a longer period upon their host. * They lose the 
 power of locomotion they previously possessed, since their extremities 
 atrophy in consequence of disuse, and become stunted in their growth 
 
 1 I have followed in the account given above the usually accepted view, but I may 
 add that the transformation of the snail into the so-called snail-sack, has not as yet been 
 directly observed. 
 
 2 See v. Nordmann, Mikroyraphitche JBeitrdge, Bd. ii. : Berlin, 1832. 
 
DIFFERENT DEGREES OF PARASITISM. 93 
 
 according to the degree to which their parasitism becomes stationary. 
 Likewise, also, the sensory perceptions, with their corresponding organs, 
 degenerate. The body loses its segmentation, and finally becomes 
 changed into a cylindrical mass, which not only swells considerably 
 under the pressure of the rapidly growing sexual organs, especially 
 the ovaria, but often becomes deformed in a most irregular manner. 
 Such extreme cases are exhibited among the Copepoda by the Ler- 
 naeadse, 1 among the Isopoda by the Entoniscidse, 2 which live an 
 entirely entozootic life. 
 
 But even in these extreme cases the parasitic Crustacea possess, 
 in their young state, the same organization as do the allied free-living 
 forms, and, with a similar form, they lead also at first a similar life. 
 The transformation into the definitive condition is slow and gradual, 
 and is brought about by a metamorphosis which runs parallel with 
 every change in the relations of life. 3 That the metamorphosis is 
 retrogressive on the whole, and that it advances to different degrees 
 according to circumstances, has been mentioned above ; I will only 
 add that in correlation with a previously mentioned fact (p. 44) 
 it often reaches a higher degree in the female than in the male. 
 
 In the same manner also, as in the case of the parasitic Crustacea, 
 the natural relations of the Gregarines, of the itch-mites, and of the 
 mosquitoes, may be determined to the free -living forms related 
 severally to each of them. But among the parasitic insects there are 
 forms in which the relations are less evident, and the intermediate 
 connecting links are wanting. For instance, the lice and fleas stand, 
 notwithstanding their large number of species, to a large extent 
 isolated from their related forms. They possess characteristics so 
 different that no connecting links have as yet been found, so that even 
 the systematic position of these animals appears in no way deter- 
 mined. The same is the case with the greater number of the so-called 
 intestinal worms. The groups Cestodes, Trematodes, and Acantho- 
 cephala consist entirely of parasites, although they differ from each 
 other in the degree of their parasitism, especially the Trematodes. 
 The tape- worms and Acanthocephala are capable only of a parasitic 
 life, through the want of a mouth and alimentary canal ; for a free 
 life presupposes the capacity of taking up nutritive substances into 
 the body directly by means of a permanent or temporary opening. 
 
 Among the intestinal worms there is only a single group which 
 
 1 C. Glaus, " Beobachtungen iiber Lernaeocera, &c. :" Marburg, 1866. 
 
 2 Fr. Mliller, Archiv fur Naturyesch., Jahrg. xxviii., Bd. i., p. 10, 1862 ; Jenaische 
 Zeitschr., Bd. vi., p. 53, 1867 ; and Buchholz, Zeitschr. f. idss. Zool., Bd. xvi., p. 103, 
 1866. 
 
 8 See Glaus, " Beitrage zur Kenntniss der Schmarotzerkrebse," Zeitschr. f. wiss. Zool., 
 Bd. xvi., p. 365, 1864. 
 
94 THE ORIGIN OF PARASITES. 
 
 has related forms living in the free state, and that in considerable 
 numbers, namely, the round-worms, or Nematodes. But the free-living 
 Nematodes have only recently become the subject of a close investi- 
 gation. 1 Only a few decades ago, scarcely half a dozen of these forms 
 were known, and these only imperfectly, so that naturalists, mistaking 
 their natural relations, were inclined to class them with the Infusoria 
 rather than with the Nematodes. Under such circumstances it seems 
 easy to understand how the older helminthologists entertained the 
 view that the internal parasites stood isolated, not only biologically 
 but also systematically, from other animals. They united them into 
 a single class (Entozoa), which, although nearly approaching the free- 
 living worms, was understood to have no close relation to them. It 
 will be obvious that such a connection helped greatly to displace the 
 processes of entozootic life from their natural connections. Under its 
 influence parasitism appeared in science as a phenomenon sui generis, 
 which could not be judged according to the laws of ordinary animal 
 life, but, on the contrary, was thought to be opposed to these in many 
 of its relations. On a former occasion (p. 22 et seq.) it has been 
 shown at length how for a long time special and peculiar laws were 
 supposed to govern the existence and origin of the Entozoa, and 
 howthese had been invented, for the most part by systematic 
 helminthologists, until they ultimately learned to judge facts more 
 correctly and more in accordance with nature ; and thus the relations 
 of the Entozoa to the free-living animals have found a more proper 
 recognition. 
 
 As has been mentioned, the relations are most evident among the 
 Nematodes, which are a group of animals whose representatives, far 
 from being exclusively Entozoa, have in the free state such a wide dis- 
 tribution, and under such varying circumstances, that the number of 
 parasitic forms, although also great, is far outbalanced by the former. 
 It would, of course, be impossible here to attempt a full description 
 of these free Nematodes. For our purpose, it will be sufficient to 
 remark that they live in the sea, in fresh water, in mud, and in the 
 earth ; and that sometimes they lead a predatory existence, at other 
 times they live on decaying matters. To the latter belong the best 
 known and most widely distributed forms, the species of Dujardin's 
 genus Rhabditis, above mentioned (Leptodcra ; Pelodera, Schneider). 
 They are animals of small size, which live everywhere in large num- 
 bers where the earth is impregnated with decaying organic substances, 
 and differ from their related forms, especially in the structure of 
 their alimentary and sexual organs. Especially characteristic is the 
 highly muscular ossophageal tube, which encloses in its posterior 
 
 1 Especially by Bastian, Ebert, Schneider, BiitschJi, Marion, and tie Maan. 
 
FREE-LIVING NEMATODES EHABDITID^E. 
 
 95 
 
 globularly expanded portion (the so-called "Bulbus") an armature 
 usually formed of three valvular teeth (Fig. 60). Sexual maturity is 
 attained only through abundant nutrition, mostly only in places where 
 a mass of decaying matter has been formed. 
 In such localities the generations follow upon 
 one another often so closely, that the young- 
 worms may be found there in large numbers and 
 in all stages of development. When this decay- 
 ing matter ceases to exist, either through being 
 exhausted or dried up, then the creatures scatter 
 and continue in the larval state, until some 
 favouring fortune grants them the possibility of 
 further development. In this young state, pro- 
 vided with a cystic larval membrane (with oc- 
 cluded mouth and anus), they can withstand 
 desiccation for a considerable time without perish- 
 ing. Under certain circumstances these mouth- 
 less larvae reach the interior of living animals, 
 where they then, evidently in consequence of 
 their parasitism, enter upon a course of develop- 
 ment which differs considerably from their usual 
 life-history. This is specially the case with a 
 species which was first described by its dis- 
 coverer, Schneider, under the name Alloionema 
 appendiculatum^ though he has more recently FIG. 
 correctly recognised it as a Ehdbditis (Lepto- 
 dera). 2 The researches of Schneider, and more especially of Glaus, 8 
 show that the parasitism of this interesting form is a purely optional 
 one, and that it can be abandoned without change of its specific 
 characters. In the latter case the life-history follows the ordinary 
 course ; but it is otherwise when the larvae have the opportunity 
 of migrating into the black slug (Arion ater). In this they de- 
 velop into animals which reach double their size (over 4 mm.), not- 
 withstanding the absence of a mouth ; they also lose the chitinous 
 oesophageal teeth and awl-shaped caudal point they formerly pos- 
 sessed, but there develop instead two finely streaked long cuticular 
 bands at the posterior extremity of the body, whose function is most 
 probably that of organs of touch, seeing that they occur also in other 
 Nematode larvae in this position. 4 The parasites, however, attain 
 
 1 Zeitschr. f. wt'ss. Zool, Bd. x., p. 176, 1860. 
 
 2 " Monographic der Nematoden," p. 159 : Berlin, 1866. 
 
 3 " Beobachtungen liber die Organization and Fortpflanzung von Leptodera appen- 
 diculata :" Marburg u. Leipzig, 1868. 
 
 4 See Vol. IT. 
 
96 THE ORIGIN OF PARASITES. 
 
 sexual maturity only after abandoning this host, when they cast 
 their skin, and lose their riband-shaped caudal appendages, while the 
 apertures of the alimentary and sexual organs break outwards 
 through the cuticle. In the sexually mature state also the size and 
 formation of the tail characterise these animals as a peculiar form. 
 Even the internal organization shows many differences. The uterus 
 contains at least 500 to 600 eggs, whilst in the female developed from 
 the free larva it encloses two or three dozen eggs at the utmost. In 
 both cases, however, the eggs develop within the body of the female into 
 embryos, which are exactly alike in size, form, and organization ; and 
 may also attain to sexual maturity in the free state in the presence of 
 nitrogenous food material, without the need of migration into slugs. 
 Hence there is no doubt that the parasitism in this case is merely 
 collateral with the free state, and is of importance in the maintenance 
 of the species only so far as in agreement with the relations pre- 
 viously indicated it affords the possibility of producing a more 
 numerous progeny. At the same time it is evident that the devia- 
 tions in the structure of the parasitic generation are in correspon- 
 dence with the altered circumstances of its life, and are conditioned 
 by them. 
 
 The appearance of parasitic generations side by side with free- 
 living ones, which in the case of the above-mentioned Rhabditis 
 appendiculata was only possible under certain circumstances, is 
 more conspicuous in other instances, and becomes ultimately a 
 constant phenomenon. The parasitic generations intercalate them- 
 selves between the free-living, in regularly alternating succession, 
 just as do the so-called " nurses " between the sexual animals in the 
 case of alternation of generations. But the intermediate generations 
 are not asexual like the nurses, which, as is well known, produce their 
 successors asexually, but they are complete sexual animals, equivalent 
 morphologically to the free-living generations, and in some respects 
 even occupying a position superior to them. 1 
 
 Such is the case with the above-mentioned Rhabdonema (Ascaris) 
 nigrovenosum (p. 2), whose Rhabditis-foTm, living in the excrement of 
 frogs, differs very little from the animals related to it. Like other 
 species of Rhabditis of small size (Fig. 61), it attains sexual maturity 
 within a short time, and produces several embryos, which are hatched 
 within the body of the female, and, as has also been observed in the 
 case of other Ehabditida?, remain there until they have completely 
 destroyed and devoured the internal organs. Also, at the com- 
 
 1 I have for some time been accustomed to call such an alternate succession of 
 dimorphous sexual generations by the name " Heterogeny." 
 
RHABDITOID PARASITES. 9/ 
 
 mencement, the young have the characteristics of the genus Rhabditis, 
 but lose them while yet in the maternal body; after they have 
 attained a certain size, they cease to eat, and undergo further de- 
 velopment only after having found an opportunity of becoming trans- 
 ferred into the lung of a frog, and thus exchanging their former mode 
 of life for a parasitic one. 
 
 The adaptation to the circumstances of parasitic life is much more 
 complete in these worms than is the case in Rhabditis appendicu- 
 
 FIG. 61. Rhabditoid form of Khdbdoncma (Ascaris) niyro- 
 venosum. A . Male ; B. Female, with embryos in 
 various stages of development. 
 
 FIG. 62. Mature em- 
 bryo of Rhabdonema 
 niyrorenosum. 
 
 lata. When they reach the lungs of their host, the young parasites 
 grow to a length of almost an inch, and possess scarcely the slightest 
 
 G 
 
98 THE ORIGIN OF PARASITES. 
 
 trace of similarity to their predecessors; they live for several 
 months, during which time they produce a countless number of 
 eggs, which are hatched while yet in the uterus, and afterwards 
 pass into the intestine of their host. During their stay in the 
 intestine the embryos escape from the shell; they again become 
 small perfect Ehabditidae (Fig. 62), and remain in this form in the 
 cloaca, unaltered, until they are expelled with the excrement, when, 
 if surrounded by putrescent matters, they complete their life-cycle 
 in a few days. The remarkable circumstance that the parasitic 
 Rhabdonema nigrovenosum is always found only in the female form, at 
 first led me to suppose that they propagate their species by parthe- 
 nogenesis ; but I have since found as also Bischoff had previously 
 done that in several individuals there were seminal corpuscles in the 
 posterior portion of the ovary among the eggs ; so that I am now 
 prepared, with Schneider and Glaus, to regard this form as a herma- 
 phrodite, which, as is also known to be the case in certain instances of 
 free-living Ehabditidse, 1 produces seminal corpuscles in sexual organs 
 of otherwise female structure for some time before the ova make their 
 appearance. But I must add, that in many cases I have sought in 
 vain for these seminal corpuscles; and other helminthologists have 
 also experienced the same difficulty e.g., von Siebold so that the 
 sibility of a parthenogenetic development is not yet entirely excluded. 
 [It was to be expected a priori that Rhabdonema nigrovenosum 
 could not be the only Nematode possessing so peculiar a life-history ; 
 but the statement of Ercolani 2 as to the descent of the A. inflexa 
 and A. vesicularis of hens from certain free-living Rhabditis- forms, 
 has no foundation in fact. On the contrary, my recent researches 3 
 lead to the conclusion that the so-called Angaillula stercoralis (an 
 unmistakeable Rhabditis found in the excreta of patients suffering 
 from diarrhoea in warm countries, and especially Cochin-China) pro- 
 duces sexually a new generation, which becomes transformed in the 
 intestine into the so-called A. intestinalis, represented, like Rkabdo- 
 nema nigrovenosum, only by female individuals. The same is true of 
 a sausage-shaped anenteric Nematode (Allantonema mirabile, Leuck- 
 art 4 ), which is parasitic in the body-cavity of Hyldbius pini, and con- 
 
 1 See Schneider, " Monogr. d. Nematoden," p. 313 ; and Vernet, Arch. Sri. Phys. 
 Nat., t. xlv., p. 61, 1872. 
 
 2 Ercolani, " Sulla dimorphobiosi, &c.," Mem. Accad. Bologna, t. iv., p. 237, 1874, and 
 t. v., p. 391, 1875 ; Abstr. Journ. de Zool., t. iii., p. 67, t. iv., p. 254. 
 
 3 Leuckart, " Ueber d. Lebensgesch. d. sog. Anguillula stercoralis, u. deren Bezieh. 
 zu d. sog. A. intestinalis," Bericht d. math. phys. Cl. Tc. Sachs. Gesellsch. Wiss., pp. 
 75-107, 1882. 
 
 4 Leuckart, "Ueber einen neuen heterogenen Nematoden," Bericht d. Versamml. 
 deutsch. Naturf. Magdeburg, p. 320, 1884 ; a more detailed account will shortly appear in 
 Bericht. d. math. phys. Cl. k. Sachs. Gesellsch. d. Wiss. 
 
KHABDITOID LARVAL FORMS. 99 
 
 tains in the uterus-like terminal portion of its generative organs an 
 innumerable quantity of Khabditoid embryos, which become free by 
 boring to the exterior, and grow into mature males and females 
 without essential change of form. E. L. 1 ] 
 
 But even the single example of RJidbdonema is sufficient not only 
 to place beyond doubt the special relations between parasitic and free 
 life, but to prove further that the former, instead of being collateral, or 
 even subsidiary to the latter, as in the case of Rhdbditis appendiculata, 
 may, under certain circumstances, become more conspicuous ; the im- 
 portance of the free life, of course, becoming less in the same proportion. 
 
 This alteration in the relative importance of the two conditions of 
 life has by no means reached its extreme point in Rlidbdonema, for, 
 according to the above-mentioned (p. 61) researches, there is a whole 
 series of parasitic Nematodes (especially in the family Strongylidse), 
 among which the Rlidbditis-imm, instead of representing an indepen- 
 
 FIG. 63. Dochmitts trigonocephalus. A. Free-living young form ; 
 B. Young parasite. 
 
 dent generation which precedes the parasitic, is limited to the young 
 stage of this latter, and passes on at once into the parasitic condition. 
 After the manner of the common Khabditidse, these worms live at 
 first free in mud and damp earth, where they feed and grow until 
 they have attained a definite size. With the shedding of their skin 
 the characters of the genus Rhdbditis are lost, and also the possi- 
 bility of their former mode of sustaining life. The worms, however, 
 continue to live for some time under the former conditions, but only 
 so long as the reserve material gathered in their interior is sufficient 
 to meet their necessities. In order to grow further, and to complete 
 their metamorphosis, they must exchange their former free life for a 
 parasitic one, and only in the interior of a living animal do they find 
 the conditions for their complete development. 
 
 1 The above passage has been substituted by the author for one in the German edition 
 W. E. H. 
 
100 THE ORIGIN OF PARASITES. 
 
 Notwithstanding all differences, the constitution of the young form 
 points unquestionably in all these cases to the relations which obtain 
 between it and the Rhabditidse. The differences, moreover, are not so 
 great as they might seem at first sight, for, on the whole, they are 
 limited to the fact that the former condition of life, which was spread 
 over two generations, is now drawn together into one ; and this is a 
 phenomenon which we often meet with in animal life. I need only 
 remind the reader, by way of example, that in nearly related forms the 
 alternation of generations is often represented by a metamorphosis in 
 which the former preliminary generation is represented only by the 
 characters of the young form. 
 
 But even these traces of a former independence may be more 
 or less completely lost, for we know that besides the species with 
 alternation of generations and metamorphosis, there are very often 
 others in which the state which was passed through by the former 
 as a free larva is relegated to the period spent in ovo ; so that 
 thus birth occurs at a stage of development which was previously 
 attained only in the free state. In such cases, of course, all those 
 properties remain latent which enabled the respective conditions to 
 obtain external manifestation ; and the form which in the previous 
 case was living and mature, is now indicated only in sucli faint outline 
 as is necessary for accomplishing the transit into a new stage of de- 
 velopment. Such being the case, we have, then, no right to make the 
 existence of a Ithabditis-like larva the exclusive criterion for the rela- 
 tions which obtain between the parasitic and free-living Nematodes. 
 By means of a continuous and ever-increasing adaptation to the con- 
 ditions of parasitism, this larval form may disappear, or, more correctly, 
 it may become unrecognisable in the processes of development in ovo. 
 Through such abbreviations of the history of development there may 
 then arise forms like Oxyuris, Trichoccphalus, Spiroptera, and others, 
 with embryos, which are not hatched in a free state, but remain in the 
 egg until they have found a host (p. 66). 
 
 The differences which exist between these species must of course 
 be considered in exactly the same way as the specific differences 
 between free-living creatures. In every case the characters of an 
 animal are the factors which determine its mode of life; so that 
 if two animals deviate from each other, their capacities also vary, 
 and that in exact proportion to the degree in which they differ 
 Trwhocephalus and Spiroptera live under other conditions than Oxyuris. 
 Although they are all Entozoa, and even inhabit the same organs, yet 
 they differ in manner of locomotion, nutrition, and propagation, as well 
 as in other functions. It is these very differences which find expression 
 in the peculiarities of the external and internal structure, since the 
 
ABSENCE OF A RHABDITOID STAGE. 
 
 101 
 
 animal-body is plastic, and capable of adapting itself to the con- 
 ditions of a specific mode of life. Hence we must leuve it doubt- 
 ful whether the unmistakeable similarity which 
 Oxyuris (Fig. 64) presents in many respects 
 (especially in the form of the body, structure 
 of the alimentary canal, and sexual apparatus) 
 to Rhabditis, is the consequence of such a 
 secondary adaptation; or whether it may be 
 interpreted as a mark of closer genetic rela- 
 tion. But it is not only the developed animals 
 which present such conditions of adaptation, but 
 also the embryos. Whether these remain where 
 they have become free, or forsake the place of 
 their birth and migrate ; whether in their migra- 
 tion they break through tissues and organs of a 
 particular character ; whether their locomotion be 
 rapid and energetic or not ; all this finds expres- 
 sion in form and structure, and often expresses 
 itself in forms which, notwithstanding a common FlG QL _ 0xyuris ambifjua 
 type, frequently differ widely from each other. (young). 
 
 In this way may also be explained the fact that there are Nema- 
 todes whose embryos exist without a fthabditis-foim for a time in the 
 free state, until they migrate into their host in some way or other. 
 Such embryos do not lead a true free life, like the Ehabditidge, for they 
 neither feed nor grow, but resemble free-living animals, in so far as 
 they have the power of independent locomotion. It is owing to this 
 circumstance that they are able to escape many of those casualties 
 which otherwise determine the distribution and transference of 
 helminthic germs. There are, then, certain advantages connected 
 with such a larval form, and it may be these which have brought 
 about its existence. It is plain that the form and structure of 
 the embryos change in manifold ways, according to the varying 
 conditions (locality, mode of locomotion, character of the skin to be 
 penetrated) ; and this fact is obvious on even a superficial examination 
 of the embryonic forms, say of Cucullanus or Dracunculus on the one 
 hand, and Strongyhis filaria on the other (Fig. 65), and may be estab- 
 lished even by a most superficial research. The impossibility of ob- 
 taining nutriment naturally makes it necesssary in all cases that the 
 duration of such larval stage must be short; and, generally, the 
 shorter the more lively is the locomotion which the embryo exhibits. 
 
 I must of course leave it undetermined whether I have suc- 
 ceeded in the above attempt to develop the phenomena of the 
 parasitic life among the Nematodes in correct and natural sequence, 
 
102 THE ORIGIN OF PARASITES. 
 
 from their earliest manifestation. Owing to the impossibility of 
 checking reasoning by experiment, all such attempts have a more 
 
 
 FIG. 65. Embryos, A. of Curullanu*, and B. of titrongylus Jttaria. 
 
 or less subjective character. It was not my intention to draw 
 up a phylogenetic tree for the parasitic Nematodes, since that 
 could be done only in reference to their relations, and might 
 prove illusory in a very short time. What I aimed at was not 
 more than to prove the possibility of such a relationship be- 
 tween the free-living and parasitic Nematodes as would clearly 
 allow of a derivation of the latter from the former, on the basis 
 of biological knowledge. 1 I will therefore also grant that the 
 connections may with equal, and perhaps even greater, right be 
 sought in other directions than that followed by me. Thus, for 
 instance, one might perhaps interpret the freely moving larviu which 
 I mentioned last as being allied to the Ithabditis-likQ condition of 
 other Nematodes, instead of explaining them to be only a subsequent 
 adaptation, as I endeavoured to do ; and one might, by the hypothesis 
 of one diminished function (merely of locomotion), derive them from 
 other Nematodes, and thus regard them in a certain way as degene- 
 rated Rhabditis-torms. But in fact this is somewhat deceptive, 
 especially when one considers larval forms of certain species of 
 Strongylidae, which, both by their organization and the systematic 
 position of their parents, remind us strongly of the JRhabditis-l&e 
 embryos of Dochmius and other Nematodes. Still, as above men- 
 tioned, these are only possibilities, and hence remain always arbitrary. 
 But thus much is established, that the parasitism of the Nematodes 
 
 1 BUtschli has attempted in a similar way to prove the relations that exist between 
 the free-living and parasitic Nematodes. Bcricht d. Senkenb. naturf. GcaeUach., p. 56, 
 1872. 
 
COMPLETE PARASITISM OF TRICHINA. 
 
 103 
 
 exists in various degrees, and, as a rule, attains its complete develop- 
 ment only at the expense of a free life. 
 
 The most complete case of this parasitism has not, however, 
 hitherto found a place in our exposition. I refer to Trichina, which, 
 as a rule, completes its entire life-history in the body of its host. 
 The embryos, which are born alive, soon bore through the wall 
 
 1 I ! I 
 
 IfSn 
 
 FIG. 66. Tric/iina spiralis. A. Embryo; B. 
 Intermediate form ; C. Sexual form ; 
 (unimpregnated female). 
 
 of the intestine which shelters their parents, and thus reach the 
 muscles, where they develop into a larval form, which, after trans- 
 ference into another suitable host, directly completes its growth into 
 the sexual form (Fig. 66). A lengthened existence in the free state is 
 thus entirely excluded ; even embryonic development and migration 
 occur during the period of parasitic life. It is exceptional, and only 
 
104 
 
 THE ORIGIN OF PARASITES. 
 
 in rare cases, that embryos expelled from the body along with the 
 fseces can effect a transference. 
 
 The Trichina, indeed, furnish the only instance of a parasitism 
 which has lost every relation to the outer world. The Trema- 
 todes and Cestodes, as well as the Acanthocephala, are, without 
 exception, governed by the law that in their young conditions 
 
 FIG. 68. Distomum 
 (natural size) 
 
 FIG. 67. Tcenta mcdiocandlata 
 (natural size). 
 
 they reach the external world either as freely-moving embryos, 
 or at least as eggs, and from thence they return into their hosts, by 
 means either of an active or passive migration. We know of no case, 
 
AFFINITY OF CESTODES TO TREMATODES. 105 
 
 however, in which, among these Helminths, the free life of the larva 
 attains to greater biological independence than I have proved in 
 various ways to be the case among the Nematodes. Where we do 
 meet with a free larval form among them, its function is limited to 
 the search for and invasion of a suitable host (p. 61). Everywhere, 
 during this period of free life, nutrition and growth are in abeyance. 
 
 It is evident, and has indeed been mentioned above, that on account 
 of this fact the proof of the relations to free-living animal forms is 
 made considerably more difficult. On account of an extensive adap- 
 tation to the conditions of parasitic life, the systematic characters of 
 the animals in question are considerably modified, and often rendered 
 wholly unrecognisable. 
 
 Among the groups here mentioned there are two, the Cestodes and 
 Trematodes, which are very nearly related to each other, so nearly 
 indeed, that it is difficult to draw a clear distinction between them. 
 This announcement may seem startling, when merely the external 
 form of a Tcenia (Fig. 67) and of a Distomum (Fig. 68) is taken into 
 consideration, for at first sight there are scarcely two other Helminths 
 which differ so widely from each other in their external appearance. 
 
 In one case, we find a ribbon-like body, perhaps some metres 
 in length, with head and segments; in the other, a body short, 
 simple, and flat ; in the one, suckers on the circumference of the 
 head, in the other, in the middle line of the anterior portion of 
 the body; in the former, an absence of mouth and of intestine, 
 in the latter, a well developed alimentary apparatus. Who, at 
 first sight, would expect to find resemblances among such oppos- 
 ing characters? But the question assumes another aspect, when 
 we recognise that what we call a tape- worm is not a single animal 
 like a caterpillar or millipede, but a whole colony, which furnishes 
 segments in regular succession, immediately behind the so-called 
 " head," which also represents a specialised individual the " Scolex " 
 (p. 37). Not the whole worm, but the single segment (Proglottis) 
 must be compared with the fluke ; and then we shall find, especially 
 in the structure of the sexual apparatus, which constitutes by 
 far the greatest portion of the whole internal organs, that there 
 are so many and such surprising similarities, that the close relation- 
 ship can no longer remain doubtful. Of course there are certain 
 differences between the two forms, especially in respect of the in- 
 testine and of the organs of attachment, but even these lose their 
 importance as soon as we extend our comparison over a large number 
 of species. 
 
 In the first place, it has been shown that among the entopara- 
 sitic Trematodes there are a number of species which, like the 
 
106 THE ORIGIN OF PARASITES. 
 
 Cestodes, have no alimentary canal. 1 In the case of a large free- 
 living animal such a want would, of course, be a very remarkable 
 circumstance, since the possession of mouth and intestine is, according 
 to our present knowledge, a most necessary requisite of such animals. 
 But the relations of parasitic life, which permit of nutriment being 
 taken up through the skin, render the possession of these organs un- 
 necessary, or at least not indispensable (p. 18). Even in Nematodes 
 we see the intestinal canal become atrophied in a few cases. This 
 proves no more than that the parasites in question are so completely 
 adapted to the conditions of their existence, that they have no further 
 need for an intestine, and hence we can only interpret the absence 
 of this organ in the Cestodes as meaning that they are much further 
 removed from the conditions of free life than the Trematodes. 
 
 But the absence of hooks in the proglottides, like the absence of 
 an intestine, results from the relations given above. They do not 
 stand in such need of them as the solitary living Trematodes, since 
 they belong to a community which is sufficiently firmly fastened by 
 means of a hook apparatus, with which the so-called head is provided 
 (Fig. 4) ; the individual segments of the chain have thus a certain 
 share in the hook apparatus situated on the head. 
 
 If further proof of this assertion were required, it might be found 
 in the existence of certain unsegmented Cestodes, which, like Gary- 
 ophyllceus, Amphiptyches, &c., represent in their simple body both head 
 and proglottis, that is, unite in themselves both a hook-apparatus 
 and sexual organs like the Trematodes. That which in the common 
 tape-worm was spread over two generations (head and sexual animal) 
 has in these animals again become united in a single individual : and 
 this has been pointed out above to be a frequent occurrence among 
 these groups which present alternation of generations for it is an 
 alternation of generations which manifests itself in the mode of de- 
 velopment of the tape-worms. 
 
 The above-mentioned facts leave no room for doubt that the Ces- 
 todes are very closely related to the Trematodes, that they represent 
 in a certain sense Trematodes without an intestine, in which the 
 organism has, according to the law of alternation of generations, 
 separated itself into two genetically combined individual forms. 
 That this affords certain advantages of great importance, especially to 
 animals exposed to so many vicissitudes, as is the case with the intes- 
 tinal worms, is apparent, especially when we remember that the young 
 tape-worm (Scolex) is rendered capable, through the alternation of 
 
 1 Such is the case, according to a letter which I have received from Prof. Glaus, in a 
 Trematode allied to Distomum from the intestine of Delphiiius dclphis, as also, according 
 to van Beneden, in Distomum Jillicollc. Dr. Tasehenberg will shortly prove that these 
 examples by no means complete the list of anenteric Trematodes. 
 
AFFINITY OF TREMATODES TO HTRUDINEA. 107 
 
 generations which it undergoes after transference to its definitive host, 
 of multiplying the number of its descendants by the number of the 
 sexual animals which it produces. This fact also proves that the 
 tape-worms are Helminths, which have adapted themselves much more 
 completely to the conditions of parasitism than the Trematodes. 
 
 If tape-worms are in reality to be regarded as creatures which have 
 sprung through a further adaptation to the conditions of parasitic 
 existence, from Trematodes or Trematode-like ancestors, then the ques- 
 tion regarding the origin of these two groups resolves itself into one 
 that is to say, the inquiry concerns itself only with the relations which 
 the Trematodes bear to free-living worms. 
 
 In the discussions of this question only two groups of known 
 animals can be considered here ; these are the leeches and the Plan- 
 arians, both of which show in their external appearance and internal 
 structure a manifold resemblance to the Trematodes. The leeches, 
 by their mode of life, show an analogy with the Trematodes, for it is 
 well known that the greater number of them live as parasites, although 
 they are to some extent predatory (Aulastomum vorax, for instance, 
 feeds chiefly on earth-worms and snails). The smaller and weaker 
 forms of leeches are almost as persistent in their parasitism as the 
 ectoparasitic Trematodes, some of which they also resemble in size 
 and appearance (e.g., Astacobdella, which is parasitic upon the cray-fish, 
 and Udonella parasitic upon Caligus). One might indeed be easily 
 tempted to imagine a direct connection between these two groups. 
 
 But upon closer comparison there are considerable difficulties 
 opposed to this hypothesis. Not only do the leeches possess a dis- 
 tinctly segmented body the segmentation being evident also in their 
 internal structure, especially in the formation of their nervous system 
 and excretory organs but also the mode of their development and the 
 organization of their embryos manifest many and vital differences from 
 the Trematodes, which at present forbid any attempt to connect them. 
 What similarity there is between the two forms is either more ap- 
 parent than real (structure of the intestine and sexual organs), or is 
 only found in points of inferior importance (possession of suctorial 
 discs, absence of body-cavity). It is evidently more in accordance 
 with our present knowledge of the morphological relations of the 
 Hirudinea to regard them as parasitic forms allied to the earth-worms, 
 than to connect them with the Trematodes. 
 
 But if the Hirudinea do not furnish a link to the Trematodes, 
 there remain only the Planarians which can be regarded as their 
 ancestors. These prove in reality to be very closely related to 
 the Trematodes in their general structure, and the formation of their 
 individual organs, In both cases, the short unsegmented parenchyma- 
 
108 
 
 THE OiUGIN OF PARASITES. 
 
 FIG. 69. Ciliated Embryos of A, Ditto- 
 mum hepaticum, and S, of Monostomum ca- 
 pitellatum ; the former with an eye-speck. 
 
 tous body contains a many-branched alimentary canal without anus, 
 and with a powerful pharynx and a strongly developed hermaphrodite 
 sexual apparatus. The same agreement obtains in the structure and 
 
 arrangement of the excretory vessels, 
 the nervous system, and the muscles. 
 Even in respect of the histology 
 there are many similar agreements. 
 Finally, since the embryonic condi- 
 tions also manifest great similarity 
 to each other, there remains a differ- 
 ence between the two groups, only 
 inasmuch as the one consists of free- 
 living animals, the other contains 
 only parasites. The specific peculi- 
 arities, however, of the Planarians, 
 as well as of the Trematodes may 
 be ascribed to this difference ; since 
 the possession of a ciliated epithe- 
 lium and special organs of sense, as 
 we find them in the Planarians, cor- 
 respond with the requirements of a 
 free life, exactly in the same way as 
 the presence of a hook-apparatus does to the conditions of parasitism. 
 The free swimming young forms of the Trematodes even their 
 entozootic species are mostly provided with the ciliated epithelium 
 of the Planarians, and often also with the eye-specks of their free- 
 living relatives (Fig. 69). 
 
 There are forms, even in the fully developed condition, which 
 serve as connecting links between the two groups. As there are 
 numerous species of Trematodes which, instead of inhabiting the 
 internal organs, live upon the external surface of their host, 
 and approach free-living animals in their pigmentation and pos- 
 session of eyes, so also we are acquainted with Planarians, the 
 posterior extremity of whose body presents a discoid organ of 
 attachment (Monocelis caudatiis, Oulian.), or even bears a true 
 sucker (Monocelis protractilis, Greeff), by the help of which they 
 attach themselves to foreign bodies. Leidy erects the Planaridse, with 
 a suctorial disc at the posterior extremity of the body, into a distinct 
 genus (Bdellura), and describes in it a species (Bdellura parasitica) 
 which lives on the gills of Polyphemus occidentalis, and presents an 
 instance of a true parasite. * Apart from the ciliated epithelium, it 
 
 1 Here may also be mentioned Malacobdclla, which was for a long time classed among 
 the Trematodes, and, like the Entozoa, is parasitic in shell-fish, but notwithstanding belongs 
 
AFFINITY OF TREMATODES TO PLANABIANS. 109 
 
 would be difficult to distinguish such forms from ectoparasitic Trema- 
 todes. But this ciliated coating is lost as soon as the parasitism 
 becomes stationary or permanent, and the change of the host takes 
 place only during the larval period. 
 
 After these observations, the relationship of the Trematodes to the 
 free-living Planarians may be taken as established, so that I may omit a 
 comparison of the young forms of these two groups. I will only men- 
 tion that the above described (p. 30) peculiar developmental relations 
 of the embryos of Monostomum mutabile occur also in certain worms 1 
 closely related to the Planarians, perhaps even in the Planarians 
 themselves. Likewise the fact that the embryos of the entozootic 
 Trematodes often leave the egg without a differentiated intestine, and 
 sometimes (namely, when they develop into the so-called " sporocysts," 
 Fig. 49, p. 71) never possess such an organ, will hardly seem peculiar 
 in creatures resembling the Planarians. It has been proved that there 
 are forms among the free-living Planarians which are devoid of a proper 
 intestine (Acoela, Oulian.), its place being occupied by a readily move- 
 able mass of protoplasm, which absorbs the nutriment that passes in 
 through the mouth, as is well known to be the case in the Infusoria. 
 
 The absence of an intestine in the internal parasites is thus not in 
 all cases the result of a retrograde development, but, under certain 
 circumstances, also the sign of an imperfect differentiation ; and this 
 is the case not only in the embryos of the above-mentioned Distomidse, 
 but also in those of the tape-worms, in which it is impossible to find 
 even the rudiment of an intestine. 2 This is a further proof that these 
 latter animals are far more completely adapted to a parasitic life than 
 the other related parasites. This is much more strikingly shown in 
 the Tseniadse, however, than the Bothriocephalidae, by the fact that the 
 former do not even possess the embryonic ciliated coating which is 
 seen in the young forms of the latter (Fig. 70), as in the Trematodes, 3 
 and which, as in these, subserves the function of free locomotion. The 
 
 (as had been supposed to be the case by me in 1848) to the Nemertines, a group closely 
 related to the Planaridse. 
 
 1 In this connection, see the observations concerning the so-called "Desor's Larva," 
 Max Schultze, Zeitschr. f. wiss. ZooL, Bd. iv. } p. 179, 1853; and Krohn, Mutter's Archiv 
 f. Anat. u, Pliysiol., p. 293, 1858, and especially Barrois, " Mdm. sur 1'embryologie des 
 Nemertes,".47m. Sci. nat., se>. 6, t. vi., p. 1, 1877. 
 
 2 Huxley considers this circumstance so important, that it causes him to doubt the 
 origin of the Helminths without intestine from animals with intestine ; and he throws out 
 the suggestion that they may be independent of free forms, and be directly and continu- 
 ously developed forms, that were from the commencement parasites without intestine. 
 See " Anatomy of Invertebrated Animals," pp. 213, 652, 675 : London, 1877. 
 
 3 In many cases also among the Trematodes, and even Distomidae, the embryos are 
 without a ciliated coat. Von Willemoes Suhm classes among the 28 known embryos of 
 Trematodes 10 non-ciliated forms (Zeitschr. f. wlss. ZooL, Bd. xxiii., p. 339, 1873). 
 
no 
 
 THE ORIGIN OF PARASITES. 
 
 embryos of the Tamiadre, like those of the Trichocephalidre and other 
 Nematodes, reach their hosts while yet enclosed in the egg-shell. 
 
 A similar form of parasitism is that of the Acanthocephali, which 
 resemble the tape-worms in having no intestine, and are therefore 
 by many zoologists united with the latter into one systematic group 
 (Anenterati). In favour of such a conception, one might adduce 
 the analogies which obtain between the two groups, and are especially 
 noticeable when the structure and mechanism of the proboscidean hook- 
 apparatus (Fig. 71) of the Tseniadre, with their cylindrical rostellum, and 
 of the Tetrarhynchi are brought into comparison. But all these simi- 
 larities prove scarcely more than a certain agreement in the conditions 
 of life. They represent merely adaptive relationships, and since the 
 
 . 
 
 FIG. 70. Free-swimming embryo of 
 Botltriocephalux latits. 
 
 FIG. 71. Echinorhynfltus sp!rula, natural 
 size (after Westrumb). 
 
 morphological structure in the two groups manifests the greatest 
 differences, they by no means permit the conclusion of a genetic 
 relationship to be drawn. The presence of a muscular body-wall 
 separated from the internal organs not to speak of other peculiarities 
 prohibits their association with the flat-worms. 
 
 It is indeed useless to seek in other directions for forms with 
 which the Acanthocephali naturally agree. For a time it was 
 supposed that they were allied to the Sipunculids, and might be 
 regarded as parasitic forms of this group. But in this case also it was 
 only a superficial similarity which gave rise to this view, the more so 
 
RELATIONS OF THE ACANTHOCEPHALI. Ill 
 
 as it was confined almost exclusively to the external formation of the 
 body. 1 The internal organization of the Sipunculidre shows scarcely 
 any close relation to the Acanthocephali, unless the presence of an 
 unsegmented dermal muscular tube be regarded in this sense. Also 
 the fact that the gulf between the two groups is not bridged over 
 by any intermediate forms, further lessens the probability of a re- 
 lationship between them. We know, however, thanks to recent 
 researches of a parasitic animal closely related to the Sipunculidae, 
 namely, the male of Bonellia, which (p. 10) lives as a parasite in the 
 sexual passages of the female ; but nothing in the animal betrays 
 approximation to the Acanthocephali. The structure reminds one 
 rather of the condition in the Planarians, or the ciliated embryonic 
 condition of other worms. Also the similarity to the peculiar genus 
 EcJiinoderes 2 is limited to certain external characters (the presence 
 of hooks upon a conical head), and does not justify the opinion of a 
 genetic connection. 
 
 But though it must be confessed that no group of animals can be 
 adduced to which the Acanthocephali could be directly traced, this 
 fact does not, of course, in any way involve the conclusion that they 
 have no relation to any other forms. This only may be learned from 
 it, that these relationships, instead of being manifest as in other cases, 
 are of a more hidden nature; in other words, that the Acantho- 
 cephali are related to forms of animals which have succumbed to a 
 deep-seated modification before the typical structure of the parasites 
 in question was developed. The dropping out of the intermediate 
 members, of course, causes the position of these worms to appear very 
 isolated. If, from this point of view, we search for forms which might 
 be considered as the starting-point of the Acanthocephali, then our 
 attention will soon be drawn to the Nematodes, which like them are 
 parasitic. I will base nothing on the fact that there are thread- worms 
 which, being provided with a proboscidiform and armed cephalic ex- 
 tremity, have occasionally been considered as Echinorhynchi. An 
 erroneous interpretation cannot have the force of proof. But this would 
 have been almost impossible, had not so many other similarities ob- 
 tained between the two forms. In fact, both possess an elongated 
 cylindrical body, the walls of which are formed of a strongly developed 
 dermal muscular tube, surrounded by a firm integument. This tube 
 is traversed by longitudinal vessels, and encloses a distinct body- 
 
 1 Schneider also attempts to support the relationship with the Sipunculidse by means 
 of the structure of the muscular apparatus, which in its arrangement differs from the 
 conditions found in the Nematodes, and agrees more with those of the Sipunculidse 
 (Mutter's Archivf. Anat. u. Physiol, p. 592, 1864). 
 
 2 See especially Greeff, Archivf. Naturgcsch., Jahg. xxxv., Bd. i., p. 72, 1869 ; and 
 Pagenstecher, Zeitschr. /. iviss. Zool, Bd. xxv., Suppl., p. 117, 1875. 
 
112 THE ORIGIN OF PAEASITES. 
 
 cavity, which in both cases contains a well developed male or 
 female sexual apparatus, whose differences, although apparent even 
 on a superficial view, are scarcely more marked than those found 
 in the structure of the same apparatus in the Chsetopoda or the 
 Turbellaria. According to the above remarks, the absence of intestine 
 in the Acanthocephali can scarcely be regarded as an important dis- 
 tinction. But the proboscidiform apparatus also, although of compli- 
 cated and peculiar structure, cannot form an objection to the existence 
 of a relationship with the Nematodes, since we are acquainted among 
 the Cestodes both with forms provided with and devoid of a proboscis 
 (e.g., Bothriocephalus). 
 
 In conclusion, we may remember that the Acanthocephali mfani- 
 fest also in respect of their histology many resemblances to the con- 
 ditions which obtain among the Nematodes. Among other things, 
 both agree in the structure of the muscular fibres and the ganglia, in 
 the cuticular character of the connective tissue, in the often colossal 
 size of their cells, and in the complete absence of ciliated epithelium. 
 On consideration of these facts, it becomes evident that the Acantho- 
 cephali must be regarded as peculiarly modified Nematodes. The 
 relations of these two groups may be rightly compared to those which 
 obtain between the tape - worms and Trematodes ; that is to say, 
 the Acanthocephali may be regarded as forms of Nematodes which 
 have adapted themselves to the parasitic conditions of existence, 
 to a higher and more complete degree than the others. The 
 character of the young forms agrees with this conception, and we 
 are led to believe that they are more closely related to the original 
 conditions, because they are (according to my 
 observations) provided with the rudiments of an 
 intestine, 1 in which one can discern, notwith- 
 standing its incomplete differentiation, a pharynx 
 and an intestine. An oral aperture is wanting ; its 
 place is occupied by a grove in the form of a slit, 
 surrounded by a varying number of setae, em- 
 bedded in the retractile cephalic extremity (Fig. 
 72). On comparing this young form with the 
 common embryonic forms of the Nematodes, it 
 would seem as though the above asserted similarity 
 FIG. 72. Embryos wcre on ^ y a slight one ; but this opinion changes 
 
 of Eclimvrhynchus an- ? P 5 
 
 c/ustatus;A. the profile; when we consider the embryos of the genus Gor- 
 B. ventral view. ^^ ^ n w hi c h we mee t w fth relations (see specially 
 the illustrations published by Villot) which in fact differ only very 
 little from those of the embryos of Echinorhynclius. Gordius is a 
 
 1 See Vol. II. 
 
GORDIUS AND ECHINORHYNCHUS. 113 
 
 thread-worm which differs from the real and typical Nematodes in 
 many respects, among which may be mentioned the atrophy of the 
 intestine, and the terminal position of the male and female sexual 
 apertures, characters which approximate it to the Acanthocephalidse. 
 This is, however, only an additional reason for laying greater stress 
 upon it, since we have every reason to consider the Acanthocephalidre 
 as yet more modified forms. 
 
 The changes which lead the embryos of Gordius to their ultimate 
 structure are unfortunately yet unknown to us. This fact is the more 
 to be regretted, as they may acquaint us with relations which would 
 bring the strange and in many ways remarkable metamorphosis of the 
 EchinorJiynchi* nearer to the usual process of development than has 
 hitherto been the case. In the meantime, in considering their re- 
 lationship, we can lay only slight stress upon these peculiarities, for 
 we are well aware that the developmental history often pursues various 
 courses even in closely related animals ; in one case it may be direct, 
 and hasten rapidly to its goal, in another, it may reach its conclusion 
 by a circuitous route, passing through metamorphosis and alterna- 
 tion of generations. The course of development of the Echinorhynchus 
 is merely a metamorphosis a metamorphosis, too, than which nothing 
 more thorough and complete could be imagined, since in its course 
 almost everything that the fully developed worm possesses is formed 
 anew out of the older structures. 
 
 After the foregoing account, the reader may decide for himself 
 whether, and how far, I have succeeded in discovering the relation- 
 ships of the Helminths, and in proving that they have originated 
 from free-living worms by adaptation to a parasitic mode of exist- 
 ence. But even suppose the matters just discussed were proved 
 facts, and not mere possibilities, even then much in the life-history of 
 these animals would remain problematical. We could only conclude 
 from this that a worm is capable of exchanging a free life for a 
 parasitic one, and of adapting itself in structure and mode of life to 
 such altered conditions. Instead of a free creature, the worm be- 
 comes a parasite, which departs, more or less, from its original form 
 according to circumstances. It now attains sexual maturity in the 
 interior of its host, instead of, as formerly, in the free state. It pro- 
 pagates, and generally, in consequence of the favourable circumstances 
 of nutrition, has usually a very numerous progeny, which pass to 
 the exterior, and perhaps for a time live freely, but finally develop 
 into sexually mature parasites. 
 
 This is so in many instances, not only in stationary parasites, but 
 also in many Entozoa, though very seldom ; for, as a rule, the first host 
 
 1 See Vol. II. 
 H 
 
114 THE ORIGIN OF PARASITES. 
 
 does not bring the intestinal worm to complete development, but to a 
 certain more or less advanced stage, after which the parasite attains 
 maturity only after transference into its definitive host. 1 The 
 intestinal worms undergo, for the most part, as has been shown at 
 length above, a change of hosts, and in consequence their life-history 
 and development are spread over two or more hosts. 
 
 Of this change of hosts we have hitherto taken no account in our 
 discussion, and yet it is clear that it is a process which not only com- 
 plicates, in an unexpected manner, the phenomena of parasitism, but 
 also requires an interpretation from a genetic standpoint before we 
 can obtain a complete insight into the nature of parasitic life. 
 
 At the outset only an ambiguous answer can be given to the 
 question of the significance and mode of origin of the so-called " inter- 
 mediate hosts," provided that we do not wish to forsake the point of 
 view we have hitherto occupied. The intermediate hosts have either 
 been interpolated subsequently into the life-history of the parasites, 
 or they were originally true definitive carriers, which formerly brought 
 their intestinal worms to sexual maturity, but have since become 
 merely intermediate, because the history of development of the in- 
 mates has extended itself over a greater number of stages by means 
 of further formation and differentiation. That we have in both cases 
 to do with a far-reaching adaptation needs scarcely to be expressly 
 mentioned. 
 
 If I express myself unconditionally in favour of the second of 
 these possibilities, it is chiefly in consideration of the fact that the fully 
 formed and sexually mature stages of the Entozoa are found, with few 
 exceptions, in the vertebrates that is, in creatures which have 
 relatively only recently originated. The Invertebrata, of course, are 
 not free from Helminths, but all the hundreds and thousands of 
 species which they shelter are, with few exceptions, young forms, 
 which require transference into a vertebrate in order to complete the 
 cycle of their development. If this do not imply that the intestinal 
 worms have arisen along with the Vertebrata, or that they became 
 extinct in their oldest representatives, with the exception of a few 
 remnants and both seem unlikely upon unprejudiced consideration 
 then the only possible conclusion is that the Helminths of the 
 Invertebrata have in course of time changed their character, and have, 
 during their further development in the Vertebrata, become mere larval 
 forms instead of sexually mature animals. In view of these facts, we 
 cannot doubt that the vertebrates afford a much more favourable soil 
 for the development of the Helminths than the invertebrates. We 
 must even admit that numerous forms have originated after the Yerte- 
 
 1 See 1 a and 6, 2 b, and 3, in the short review at the commencement of this chapter. 
 
OKIGIN OF INTERMEDIATE HOSTS. 115 
 
 brata became separated as a distinct phylum ; some, even in relatively 
 recent times, such as the Trichinae and others, whose life-cycle is 
 limited to mammals, most recently of all creatures. In many cases 
 the origin of new Helminths may have gone hand in hand with the 
 transformation, by means of which the hosts have gradually become 
 new species. 
 
 That the change of a sexually mature animal into a mere pre- 
 paratory stage (a larva) the process which we have adopted to 
 elucidate the change of hosts is biologically possible, cannot be 
 doubted in view of the analogy of the so-called abbreviated develop- 
 ment, frequently mentioned above, and whose counterpart it forms. 
 If a series of different developmental phases may contract into a single 
 continuous process, then, conversely, this latter can also spread itself 
 out into a number of such phases. This is a process to which we 
 must attribute a very important role in the formation of species ; for 
 the present larval forms are to be considered, agreeably with the 
 doctrine of descent, as the original sexually mature ancestors of those 
 species which to-day represent their ultimate condition. The sum of 
 the characters by which these latter differ from the larvae represents 
 the gain which the original animal has gradually acquired under the 
 changed relations of life, changes which become, as it were, added on 
 to earlier ones, so that the development is protracted, and sexual 
 maturity, which coincides with the conclusion of development, is 
 delayed. 
 
 The nature of those Entozoa, which are parasitic in invertebrates in 
 a mature condition, lends a yet more definite support to our supposi- 
 tion. They are, of course,, few in number, if we except the entozootic 
 Isopoda and a few others, and confine ourselves to the true Hel- 
 minths ; these belong mostly to the thread-worms. But we may 
 mention also a Trematode living in the fresh-water mussel (Aspido- 
 gaster conchicola), and a Cestode (Archigetes Sieboldi), described re- 
 cently by me, and found in the body-cavity of Scenuris. 
 
 All these forms develop, so far as we know their life-history (p. 70), 
 without an intermediate host, and attain their sexual maturity im- 
 mediately in the first host, as would naturally be the case provided 
 our supposition were correct. 
 
 In addition, the development and metamorphosis of these forms 
 are very simple, so that the respective animals are but little removed 
 from their hypothetical original form, and become sexually mature in 
 a condition which in many respects stands on a par with the young 
 and larval forms of their further advanced relatives. Thus the Nema- 
 todes, sexually mature, found in invertebrates (mostly omnivorous 
 insects and millipedes), follow closely the Khabditidse (Oxyuris) in 
 
116 
 
 LIFE-HISTORY OF PARASITES. 
 
 their development ; that is, they resemble forms to which the para- 
 sitic Nematodes bear relations, which have led us above to regard 
 them as their forerunners, and which are often seen represented in 
 their young forms. An exception must be made in the case of a 
 single very peculiar species (Sphcrrularia), which lives in the body- 
 
 FlG. 74. Aspidoyastcr conchicda. (A.) Embryo, 
 \B. ) Young animal, not yet sexually mature, 
 (after Aubert). 
 
 FIG. IS.Archigetes Siebddi. 
 
 cavity of the hibernating humble-bee, and shows relations of organi- 
 zation which are as yet only incompletely understood. 1 Likewise 
 
 1 See especially Sir John Lubbock, Natur. Hit. Rev., vol. i., p. 44, 1861, and 
 Schneider, " Monogr. d. Nematoden," p. 322, whose opinions regarding the life-history 
 and morphology of this strange worm differ widely from each other. [Recent investigations 
 of Schneider (Zool. Beitrage, Bd. i. , p. 1, 1884) have made us acquainted with the interesting 
 fact that the young Sphctrularia grows outside the body of its host into a sexually mature 
 animal, resembling Anyuillula, without essential change in its organization. I have con- 
 vinced myself of the correctness of this observation, and believe I have obtained proof that 
 these worms copulate while in the free condition, and that only the females find their way 
 into the humble-bees, where they develop into the paradoxical Sphcerularia. If such be 
 the case, Sphcvrularia can no longer be considered an exception to the rule above stated. 
 R. L.] 
 
SEXUAL PARASITES OF INVERTEBRATES. 117 
 
 Archigetes (Fig. 73) is, morphologically speaking, nothing else than a 
 Cysticercoid a tape-worm which concludes its metamorphosis at a 
 stage of development which, in the case of the common Cestodes, 
 represents merely a transitional form inhabiting an intermediate host. 
 Aspidogaster also (Fig. 74) is wrongly classed among the otherwise 
 ectoparasitic Polystornidse, on account of an absence of metamor- 
 phosis, whilst its structure stamps it decidedly as a Trematode allied 
 to Distonmm. Aspidogaster resembles a Redia in its mode of de- 
 velopment and the formation of its intestinal apparatus in so 
 remarkable a manner, that I see no objection to placing it, notwith- 
 standing its sexual maturity, beside the true Distomidse, and so classify- 
 ing it along with them, just as Archigetes is placed with the tape-worms. 
 The presence of a ventral sucker can as little be opposed to this 
 conception as the high development of the excretory system of vessels, 
 since both structures must be regarded merely as the result of an 
 adaptation to the animal's mode of life, which cannot be taken into 
 consideration in determining morphological relationships. 
 
 The Redise and the Sporocysts (Fig. 49), which have sprung 
 from them by a retrograde formation of the intestine, 1 are, in 
 accordance with the above discussion, to be regarded as the oldest 
 Distomidse, in the same way as the Cysticercoids are the original 
 tape-worms. This agrees with the fact that the Redise are more closely 
 related to the ectoparasitic Trematodes (specially by the structure 
 of the intestine) than are the fully formed Distomidse, and hence 
 may be more easily and readily supposed to be derived from the 
 former. It is, moreover, sufficiently known that the Redise do not 
 change directly into the mature Distomidse, but develop them in their 
 body-cavity out of so-called " germ " cells, which are of the nature of 
 eggs, and separate themselves from the body-wall (Fig. 75). The 
 metamorphosis is divided over two generations, which spring from 
 each other; it thus becomes an alternation of generations, a common 
 phenomenon, as has been shown above. The production of the new 
 brood may perhaps in this case be directly connected with the former 
 
 1 [This supposition has found an unexpected confirmation in the discovery of the 
 Orthonectida (see Giard, Jaurn. de I'Anat. et Phys., t. xv., p. 449, 1879, and Metschnikoff , 
 Zcitschr. /. wiss. Zool., Bd. xxxv., p. 282, 1881) ; or rather through the establishment of 
 the fact that these simple animals, parasitic on Ophiuroids and Turbellarians, are to be 
 regarded morphologically as sexually mature Trematode -embryos, devoid of an alimentary 
 canal (Leuckart, Archiv /. Naturgesch., Jahrg. xlviii., p. 96, 1879). Hence the Ortho- 
 nectida stand at the lowest stage of that series of developmental stages represented by 
 the Trematoda. Aspidogaster, therefore, which we have regarded as a sexually mature 
 Redia, stands higher in the series than the Orthonectida. What influence these facts have 
 upon our views of the gradual progress of parasitic life how beautifully and naturally 
 they come into accord with the views expressed in text hardly needs any further com- 
 ment. R. L.] 
 
118 
 
 LIFE-HISTORY OF PAKASITES. 
 
 existence of sexual generation ; in fact, it may in a sense be regarded 
 as the last trace of this process, especially as the germ-cells possess 
 an unmistakeable morphological similarity to ova. 1 The importance 
 which this alternation of generations has for the preservation and dis- 
 tribution of these parasites is evident. Where formerly there was 
 only one parasite there will now originate a number many dozens, 
 or perhaps even more all readily capable, under favourable con- 
 ditions, of commencing new parasitic life. 2 
 
 The newly formed Distoniidae, however, do not grow into sexually 
 mature animals within or beside their parents, but, as a rule at least, 
 
 FIG. 75. Redise, with brood of Distomes in the interior. (A.) From Paludina 
 impura (young and old) ; (B.) From Lymnceus (young and old). 
 
 forsake the host as a Cercaria, and swim about in the free state for a 
 time by means of an appendage which is not unlike the caudal bladder 
 of Archigetcs, and then migrate into a new host, generally once more 
 an invertebrate animal (p. 72). The Cercaria thus undergoes a change 
 of host, which does not immediately transfer it to a vertebrate, as is 
 usually the case, but at first to an invertebrate again, such as a snail or a 
 water insect. In the present Distomida?, also, these two hosts are both 
 
 1 This conception receives a new confirmation from the life-history of A ttantonema, 
 alluded to above (p. 98). 
 
 2 Such a proliferation in the intermediate host we find in a few Cestodes, and especi- 
 ally in Echinococcus; but in this case the young brood originates through budding, and 
 remains conn- cted with its mother-animal in the interior of the body for life. 
 
PROGRESS OF PARASITISM IN THE DISTOMID^E. 119 
 
 intermediate hosts, but we may take it for granted that such was not 
 the case from its commencement. On the contrary, these second inter- 
 mediate hosts brought their Trematodes to sexual maturity in the same 
 way as was formerly the case, according to our supposition, with the 
 Kedise. Since the caudal appendage, by means of which the Cercarise 
 swim about, is lost when they force their way into a new host, so the 
 developmental condition of these sexual animals must in the main 
 have been like the present one. 
 
 The eritozootic Trematodes are accordingly Helminths, in which 
 the change of hosts had already come about at a time when the 
 vertebrates, which are now almost exclusively concerned in it, had 
 not yet come into existence. 
 
 The supposition that the Cercarise originally attained sexual 
 maturity in their hosts, and only later developed retrogressively into 
 more intermediate forms, finds some support in the fact that these 
 animals even now, under certain circumstances, become sexually 
 mature, and produce ova in their intermediate hosts. On a former 
 occasion (p. 73, note) some cases of this kind were cited, and others 
 are continually forthcoming. These sexually mature Helminths are 
 not separate species, possessing no other sexual condition ; they are 
 rather nothing more than certain specially privileged individuals 
 belonging to species which, under other conditions, are accustomed to 
 attain their maturity only after transference into a vertebrate. 
 
 It is, moreover, a common phenomenon that the Distomidae not 
 only commence the formation of their sexual organs in the interme- 
 diate hosts, but bring them to a state of complete functional capacity. 
 This phenomenon we meet also in other intestinal worms, although 
 individual species present great variations in this respect, so that 
 many are undifferentiated sexually even when passing into their 
 definitive host. With respect to the latter, I may mention Cucullanus 
 and Spiroptera, whilst others, like Hedruris and all the Echinorhynchi., 
 assume all their external and internal peculiarities in their interme- 
 diate hosts, which is certainly a case of persistence of an earlier 
 state. Of course such differences are not without influence upon 
 the length of time occupied by the development ; instead, perhaps, of 
 weeks and months being necessary, as usual, the worm of the latter 
 kind requires only a few days, after leaving its temporary host, in 
 order to attain full maturity, and to acquire the ability to propagate 
 its species by sexual means. 
 
CHAPTER VI 
 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 PARASITIC DISEASES. 
 
 FKOM what has already been said of the life-history of parasites, and 
 especially of the Entozoa, it is evident that they influence in a most 
 important way the health and even the life of their hosts. But the 
 existence and amount of this influence was firmly established only by 
 the discoveries of recent decades. From this time a rational theory 
 of parasitic diseases, and a true insight into the deep significance of 
 this important branch of medical science, must date. Not that the 
 idea of parasitic diseases was something absolutely new; on the 
 contrary, from the earliest times men knew and feared the injurious 
 effects of these unbidden guests, and feared them perhaps even more 
 than they knew them. 
 
 In order to form a correct estimate of the pathological significance 
 of parasites, it is necessary to cast a glance at the literature upon the 
 question of the seventeenth and eighteenth centuries. 1 
 
 There was then no grievous and dangerous malady which parasites, 
 and especially intestinal worms, were not thought capable of exciting. 
 Dysentery, scurvy, hydrophobia, and even the dangerous epidemics of 
 the Middle Ages, such as plague and small-pox, were all described as 
 parasitic diseases. With each disease they associated a particular 
 parasite, just as we now sometimes speak of the cholera-Bacillus, and 
 other similar creatures, as the transmitters of certain specific diseases. 
 They supposed, further, that these originators of disease lived either 
 in the alimentary canal, or under the skin, or in the blood, and thence, 
 according to their nature, infected the whole organism in diverse ways. 
 Nor was this opinion held by individuals only, but by many, and 
 partially even by the most famous representatives of the pathology 
 of the time (Leeuwenhoek, Hartsoeker, Andry, and others). 
 
 The possibility of such extravagant opinions is now the subject of 
 incredulous wonder. To understand them it is necessary to realise 
 the condition of medical science at that time. On the one side there 
 was inaccuracy of diagnosis, and almost entire ignorance of pathological 
 
 1 I specially recommend Andry, " Traite sur la generation des vers dans le corps de 
 1'homme," Paris, 1700, of which a new edition and German translation have since appeared. 
 
EAKLY VIEWS ON PARASITIC DISEASES. 121 
 
 anatomy; on the other, the natural desire to reduce the different 
 diseases to definite etiological entities. Men then hit upon parasites, 1 
 as they did later upon magnetism and electricity, in part only because 
 they knew so little about them. 
 
 It occurred to them the more naturally to refer these diseases to 
 parasites when they observed the exit of intestinal worms and conse- 
 quent recovery; and also because, since the time of the Arabian 
 physicians, the parasitism of a mite had been recognised as the cause 
 of the widely distributed itch (see Fig. 6). In the eyes of many patho- 
 logists, the last-named fact served as direct proof of the correctness of 
 a theory from which they anticipated the weightiest conclusions as to 
 the nature of diseases. 
 
 But these hopes were vain. Although helminthological knowledge 
 was gradually more and more extended and consolidated, the idea of 
 the " Morli animati " found no new support. Men attempted in vain 
 to place beyond doubt the existence of a Contagium vivum in the 
 above-mentioned diseases. They only formed the conviction that the 
 earlier physicians, with their guesses at the existence of certain para- 
 sites, had been much too generous. The so-called "heart-worms" 
 were recognised as blood-clots, the " umbilical worms " as mere 
 fancies. The existence of the itch-mite even was doubtful, since 
 a number of experienced physicians and naturalists had sought after 
 it in vain. Observations concerning the presence of intestinal worms 
 in animals also increased, in which, in spite of this parasitism, no 
 signs of illness were noticed. 
 
 Under such circumstances, the earlier opinions became in the 
 latter half of the last century more and more discredited. 
 
 The Entozoa were still, it is true, considered on the whole as in- 
 jurious guests, which might seriously affect the health, and sometimes 
 even endanger the life of their host. But their specific relations to 
 certain diseases gradually ceased to be traced ; and there were many 
 who even denied that intestinal worms had any hurtful effects on their 
 host whatever ; some even considered their effects to be advantageous. 
 Men like Goze and Abildgaard maintained among other views that 
 intestinal worms aided digestion, by absorbing the mucus and ex- 
 citing peristaltic contractions. Jordens even called them the good 
 angels and unfailing helpers of children. 2 It was also supposed (e.g., 
 by Gaultier) that their movements and the resulting conditions ex- 
 erted a favourable influence on the development of the lungs and 
 viscera. 
 
 1 These speculations went so far, that this question, for example, was discussed (and 
 answered mostly in the affirmative) " An mors naturalis sit substantia verminosa ?" 
 - " Entomologie und Helminthologie des inenschlichen Korpers :" Hof, 1801. 
 
122 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 The belief in the absolute injuriousness of parasites, already shaken 
 by these considerations and doubts, received a still ruder shock, as 
 their wide distribution and frequent occurrence in certain animals 
 became known. Men began not only to deny the existence of speci- 
 fic worm-diseases, but to think themselves justified in maintaining 
 that it was exceptional for the parasitism to cause any disturbance of 
 health. It is true, however, that such opinions were held for the 
 most part by naturalists and helminthologists. The physicians for 
 the most part still held to the old opinions. Wherever there was 
 any doubt as to the nature and origin of a disease, worms were blamed ; 
 and " worm-irritation/' " worm-fever," and other worm-diseases were 
 very common terms both in theory and practice. And if by chance, or 
 in consequence of medical treatment, a worm left the patient, they con- 
 sidered the diagnosis verified, and the cause of the disease established 
 beyond a doubt. 
 
 The professional helminthologists, headed by Eudolphi and 
 Bremser, although, as we have said, decidedly opposing these views, 
 could not deny that certain pathological conditions, especially those of 
 the digestive apparatus, were generally connected with the presence of 
 worms. They were, however, disinclined to believe that these condi- 
 tions were directly due to worms, but sought, in accordance with their 
 theory of the spontaneous generation of Helminths, to show that there 
 were certain conditions productive of worms. They spoke of a " pre- 
 disposition to worm production " referable to definite pathological pro- 
 cesses, of a " Diathesis verminosa" which they sometimes even called 
 " verminatio," a worm disease without worms ! Thus Bremser, 1 the 
 famous Viennese helminthologist, says, " By a worm disease I mean 
 any disturbance or interruption in the functions of the primary or 
 secondary digestive and nutritive organs, whereby substances are 
 formed and collected in the alimentary canal, which under favourable 
 circumstances may, but do not necessarily, produce worms : I mean, 
 in short, the material factors of worm production. So that worms in 
 the alimentary canal are not an original disease, and indeed can only 
 rarely be regarded as a disease at all, but are much more frequently 
 the sign of the diseased state of the organs in question, or of some in- 
 terruption in the co-operation of these organs, from which state many 
 results may arise without the presence of worms." 
 
 After what has been already said concerning the life-history and 
 origin of the Entozoa, it is unnecessary to criticise these opinions 
 minutely. We may now regard it as completely established that 
 parasites do not originate from a diseased condition, but from germs 
 intruding or introduced, and they especially originate where these 
 
 1 " Lebende Wunner im lebenden Korper," p. 119. 
 
PARASITES A REAL CAUSE OF DISEASE. 123 
 
 germs find the conditions of their development fulfilled. Just in pro- 
 portion to the number of germs introduced, and to the adaptation of 
 the environment to their wants, will the number of parasites increase 
 in the individual case. 
 
 We might perhaps suppose that the developmental conditions of 
 parasites involved a certain pathological state, and might also assume 
 that parasites could not be developed except in unhealthy organisms ; 
 but in the impossibility of all proof this would only be blind adher- 
 ence to a dogma. It is true that the same has been asserted in 
 regard to the spores of fungi, and even in regard to bark-beetles 
 (Bostriclms) and vine-insects (Phylloxera), but here also the assumption 
 of a previously existing pathological state seems unwarrantable, having 
 neither proof nor probability. 
 
 What leads me most decidedly to this conclusion is the ease 
 with which even the healthiest individuals may be experimentally in- 
 fected with Entozoa. Of course, the experiment does not succeed 
 with every kind of parasite, but only, as was before explained, with 
 those which find suitable environment. Even then there may be a 
 few cases in which the expected result fails. But our former observa- 
 tions have prepared us for such experiences. For the development of 
 a parasite requires the presence not only of certain specific factors, but 
 also of many individual ones. It might even be granted that the health, 
 and especially the nature of the organism to be infected, are not without 
 effect on the imported brood (in the case above mentioned (p. 85), in 
 which, after three weeks, the heads of Tcenia ccenurus showed hardly 
 any traces of further change, the animal under investigation had been 
 used some time before for an experiment with Trichina), but we have 
 never found the slightest ground for believing that the development 
 of the invading Helminth is promoted or even conditioned by any un- 
 healthiness of the animal experimented upon. 1 
 
 Meanwhile, it is safe to assume that wherever there is a real con- 
 nection between the unhealthiness of a host and the indwelling para- 
 sites, it is the latter who are the efficient causes. 
 
 It is, however, not only on a priori grounds that we are warranted 
 in maintaining that parasites may cause even very dangerous diseases. 
 Experimental helminthology has securely established this position. I 
 
 1 Statistics, which alone can decide in this case, show, on the contrary, that certain ill- 
 nesses e.y., chronic, and especially intestinal catarrhs tend to remove parasites from the 
 diseased organ, or even to prevent their occurrence. Thus Gribbohm ( " Zur Statistik 
 menschl. Entozoen," Kieler Inauguraldissert. , p. 8, 1877), in chronic intestinal catarrh, 
 mostly in consequence of phthisical processes, found in 05 bodies only 16 (24*6 per 
 cent.), and in chronic catarrh of the large intestine in 18 bodies only 3 (167 per cent.) 
 cases of the stomachic Nematodes (Ascaris, Oxyuris, Trichocephalus), which are other- 
 wise so very frequently present (on an average in 49'8 per cent, of the cases examined). 
 
124 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 refer especially to the experiments made with Tcenia ccenurus 1 - and 
 Trichina spiralis, which may well dispel all doubt on the subject. If 
 favourably situated, a brood of these parasites acts like poison, and a 
 large dose is sure to kill the animal. 
 
 Through these experiments, not only has a foundation of fact been 
 laid for the study of parasitic diseases, but an exact method of treat- 
 ment has been attained. While little progress has as yet been made 
 in this direction, we have nevertheless established many new and 
 practically important facts. 
 
 In speaking of parasitic diseases, we mean the various disturb- 
 ances of health occasioned by these creatures, in contradistinction to 
 the views of those who speak as if there were only one "worm- 
 disease " a specific hdminthiasis. 
 
 Parasites act in very different ways, 2 according to their size and 
 mode of life, as also according to the nature of the inhabited organism. 
 Intestinal parasites produce different symptoms from brain parasites, 
 and the effects of these are different, according as they are situated in 
 the cortical layers of the hemispheres, or in the crura cerebri. In the 
 same way, Dochmius duodenalis acts differently from Oxyuris or 
 Trichina. The effects of many parasites never fail as, for example, 
 in the case of Cysticercus in the eye and Strongylus in the kidney ; 
 and in the case of others, accidental causes determine whether or not, 
 and in what degree, these effects shall show themselves. Besides the 
 situation of the parasite and the individuality of the host, the number 
 of imported germs in this connection is specially important, and to 
 this, indeed, the effects produced and the dangers incurred are ever 
 proportionate. Thus, it can be easily proved that the frightful 
 symptoms of trichinosis occur only when the parasites live in masses 
 in the alimentary canal, and thence invade the muscles 3 in still 
 
 1 Especially instructive on this subject is the result of a feeding experiment which 
 was made simultaneously in May 1854 by van Beneden in Lou vain, Eschricht in Copen- 
 hagen, Gurlt in Berlin, and by myself in Giessen, with specimens of Tcenia ccenuru* sent 
 us by KUchenmeister (then in Bautzen). The animals became ill in all the places at 
 exactly the same time, and exhibited exactly the same symptoms. Compare Haubner in 
 Gurlt's Magazine, loc. cit., Leuckart, " Blasenbandwiirmer," p. 47, or van Beneden, 
 Comptes rmdus, t.xxxix., p. 46, 1854. 
 
 8 We may take this opportunity of referring to the classical work of Davaine, 
 " Traite des entozoaires et des maladies vermineuses de 1'homme et des animaux domes- 
 tiques " Paris, 1860, 2d ed. 1877 which contains an almost complete collection of ex- 
 periments concerning worm-diseases up to date, and is full of interesting particulars. The 
 part of this work treating of natural history is not so good even in the second edition, 
 and contains many errors and anachronisms. 
 
 8 The number of muscle Trichina in an individual case has been estimated at from 
 60,000,000 to 100,000,000 a number which, on the supposition that half of the Trichina' 
 are females, and produce on an average 150U embryos, would correspond to from 100,000 
 to 120,000 sexually mature animal*. 
 
LOSS OF NUTRIMENT BY THE HOST. 125 
 
 larger masses, and that if only a moderate number be introduced, 
 hardly any disturbance of health will take place. 
 
 But perhaps the overwhelming number of parasites by which 
 man is liable to be attacked will be best realised when we state that, 
 in cases of the so-called " Cochin-China diarrhoea," the number of 
 Hhabditis stercoralis which have been known to be evacuated in indi- 
 vidual cases, within twenty-four hours, amounts to several hundred 
 thousand or even to a million. * 
 
 Three points have to be noticed in regard to the way in which 
 parasites affect their host. In the first place, they grow and breed at 
 the expense of their host, from whom they thus abstract nutritive 
 material. Secondly, they produce alterations in space as they press 
 upon the surrounding tissues or obstruct the channels in which 
 they live. Lastly, their movements, according to circumstances, 
 may give rise to pain, to inflammation, varying in degree and in 
 termination, or even to perforation and dissolution, all which 
 symptoms are, however, sometimes merely the result .of continuous 
 pressure. 
 
 The first of these three kinds of influence, although perhaps the 
 one which occurs most frequently, is seldom of much pathological 
 importance. There must be unusual influences at work, if the loss 
 caused by the abstraction of nutritive material by the parasite for its 
 metabolism, growth, and propagation is at all appreciable to the 
 host, provided that he belong to the larger animals, and much exceed 
 his parasites in size and nutritive requirements. 
 
 A Boihriowphaliis latus, seven metres in length, weighs about 27'5 
 grms. According to Eschricht, it throws off yearly a number of pieces, 
 which measure altogether about 15 to 20 metres, and may represent a 
 weight of about 140 grms. Even on the supposition that the animal, 
 which of course undergoes continuous metabolism, abstracts three or 
 four times that quantity from its host, 2 and that the nutritive 
 material consumed by all the parasites amounts to several pounds 
 yearly, it is easy to see that so moderate a quantity is of hardly any 
 account compared with the yearly consumption of the host. It is 
 
 1 Normand, " Mem. sur la diarrtioe dite de Cochin-Chine," Paris, 1877, and Davaine, 
 loc. cit., 2ded., p. 968. 
 
 2 It does not require much proof to show that Heller's method of determining the 
 host's loss of nutritive material simply by the bodily weight of the parasites is erroneous. 
 (Art. " Darmschmarotzer " in " v. Ziemssen's Handb. d. sp. Path. u. Ther.," Bd. vii., 
 Th. 2, p. 567; Eng. transl., "Cyclop. Pract. Med.," vol. vii., p. 678, London, 1877.) 
 Moreover, there are some tape-worms whose growth is so rapid that Heller's method 
 also would give extraordinary results. The tape-worm of the sheep, for example, which 
 grows to the length of a hundred metres, has been found fifty-one metres long in lambs 
 four weeks old. Goze, " Versuch einer Naturgesch., u.s.w.," p. 371. 
 
126 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 much the same in the case of the Tcenice, and even of Twnia sayinata, 
 which throws off, let us say, eleven proglottides daily, with an 
 average weight of 1*5 grms., and thus loses in the course of the year 
 about 550 grms. of organic matter. If the number of parasites be 
 greater, the association is of course more unfavourable. A female 
 thread-worm, for example, produces, as we saw before, 42 grms. of egg- 
 substance yearly ; and taking into account what it requires for meta- 
 bolism, must deprive its host during this time of at least 100 grms. 
 Thus if, as sometimes occurs, there were 100 of them (there have been 
 cases in which 1000 have been found at the same time in the in- 
 testine), they would cause a loss of 833 grms. monthly, which, under 
 some circumstances, and especially in childhood, must have a very 
 appreciable effect. Similarly, the 100,000 specimens of EhaMitis 
 stercoralis (1 mm. long, 04 mm. in diameter) which are often 
 evacuated daily by patients suffering from Cochin-China diarrhoea, 
 represent by their mass alone without 1 taking into account material 
 used in metabolism a weight of about 200 grms. And if it be con- 
 sidered further that the number of the evacuated worms may increase 
 tenfold, it becomes easy to understand how a severe marasmus may 
 ensue, even after a short illness. 
 
 I do not, however, cite these instances in support of the view 
 that the disturbances of the nutritive functions, and their manifold 
 external consequences, which the physicians were so willing to in- 
 terpret as symptoms of helminthiasis, are always to be regarded as 
 the direct consequences of the amount of nutritive material ab- 
 stracted by parasites. Even if it be certain that the disease is con- 
 nected with parasites, it is quite possible that the relation between 
 disease and parasite is of an indirect nature, and brought about by 
 the state of the infected organ. 2 Further, the continuance of any 
 disease, however slight and partial at first, will affect the general con- 
 ditions of the nutritive organs. 
 
 Nor is the nature of the materials which serve as nourishment to 
 the parasites an unimportant factor in considering the effects of the 
 association. Thus a blood-sucking parasite, cceteris paribus, causes a 
 greater loss than one which feeds on epithelial cells. To this is due 
 
 1 [As above mentioned (p. 46), these Rhabditidae are the offspring of Ancjuttlula 
 intestinalis, which had been met with in the intestine by earlier observers, but whose 
 genetic relation had remained unrecognised. Grassi and Perona have recently reported 
 that they have found AnguilluLa intestinalis in patients suffering from catarrhal gastro- 
 enteritis in Milan (Archivio scienze medic., t. iii., No. 4, 1879). R. L.] 
 
 2 A very good example is afforded by the Trichina?. In their wandering into the 
 muscular tissue they not only destroy fibres, but, by paralyzing the muscles used in masti- 
 cation and swallowing, they affect the introduction of nutriment to such a degree that 
 within a very short time the patient experiences considerable atrophy. 
 
MECHANICAL DISTURBANCE BY PARASITES. 127 
 
 the great clinical importance of Dochmius duodenalis (Anchylosto- 
 mum, Dub.) (Fig. 10), which occurs in masses in man in many tropical 
 and sub-tropical countries, and in the north of Italy, and is generally 
 so full of blood that at first sight the intestine of the patient appears 
 to be covered with leeches. As a rule, the presence of this worm soon 
 produces an anaemic condition. 1 This disease, with many others re- 
 sulting from it, is so common in Egypt, that nearly a quarter of the 
 native population suffer from it (hence " Chlorosis JSgyptiaca "), and 
 many perish for want of proper treatment, which ought of course, 
 in the first place, to be directed towards the removal of these danger- 
 ous guests. In this case we have, of course, to consider not only 
 the loss of blood which the parasites cause in filling their digestive 
 apparatus, but that which results from the bleeding of wounds caused 
 by their bites, which, according to Griesinger, 2 is often very con- 
 siderable. It is in this way that even leeches may become dangerous, 
 or even fatal, to man. 
 
 At this point it may also be mentioned that a very considerable 
 loss of blood may be caused by the haematuria produced by the 
 wandering of embryos, as in the case of Filaria Bancrofti (F. sanguinis 
 hominis) and of Distomum hcematobium. 
 
 But, on the whole, the disturbances resulting from the loss of 
 strength, and interruption of the nutritive supplies, are considerably 
 less than those which are occasioned by the growth and multiplication 
 of the Helminths. 
 
 As soon as the worms exceed a certain size, they begin, like other 
 foreign bodies, to exert a pressure on their surroundings, which in- 
 creases with their size and with the inability of the surrounding struc- 
 tures to resist it. The influence of this pressure is, of course, most 
 frequently felt in the case of the larger parasites, and especially 
 in the case of those which have taken up their abode in narrow 
 channels or in parenchymatous organs. The parts which are most 
 immediately exposed to the pressure begin to lose their character 
 and normal appearance at the points of contact with the foreign 
 bodies. The canals mnst widen when the size of the inmates exceeds 
 their normal diameter. They form sinuses, and, if the circumstances 
 permit, even change into closed sacs, which become thicker and 
 thicker through hypertrophy of the connective tissue, until they can 
 
 1 In individual cases years may elapse before the disease breaks out in full vigour. 
 The case of a workman in Vienna, who six years before had been a soldier in garrison in 
 the north of Italy, led Henschl to suppose that Dochmius duodenalis, like the D. trigono- 
 ccphalus of the dog, lives at first on epithelial cells, and only after they are exhausted 
 betakes itself to the vascular connective tissue of the intestinal villi (Mittheil. d. Vereins d. 
 Aerzte in Niederostcrreich., 1875). 
 
 * Vierordt's Archiv f. physiol. Hcilkunde, Bd. xiii., p. 554, 1855. 
 
128 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 hardly be distinguished from the cysts of the parenchyma-worms, 
 which have been described (p. 19). The soft adjacent tissue begins 
 at the same time to disappear, 1 and is finally completely destroyed, 
 after more or less remarkable histological changes. We know, for 
 instance, that the substance of the brain is gradually destroyed by 
 the growth of the bladder-worm developing within it, and that the 
 liver atrophies more and more in consequence of the ever-increasing 
 pressure of Echinococcus, or of Distomum hepaticum, which inhabits 
 the bile ducts. 2 
 
 If the pressure of the growing parasites restrict the supply of 
 blood to the infected organ, or in any other way affect its supply of 
 nutriment, the destructive work will of course advance even more 
 rapidly. In such cases the whole of the organ disappears, leaving 
 hardly any traces of its existence. Thus, in animals whose kidneys 
 are infected by Eustrongylus gigas the organ is ultimately only repre- 
 sented by insignificant sickle-shaped thickening (Fig. 76) surrounding 
 the pelvis, which has been distended by the worm into a sac-like 
 form. 3 
 
 Further, even parasites of smaller size may, under certain circum- 
 stances, achieve the same results. The tiny embryos of the Trichincc, 
 for instance* soon cause disintegration of the sarcous elements of the 
 muscular fibres which they perforate, so that the latter are transformed 
 into granular sheaths. At first these sheaths have quite the same 
 shape as the normal sarcolernma- sheaths ; but afterwards, as the worms 
 grow, an enlargement is formed around their resting-place, and this, 
 after the disappearance of its ends and other changes, becomes a 
 " TVic/traa-capsule " (Fig. 77). 4 
 
 The eggs of parasites may produce the same effects as the worms 
 themselves, if deposited in the interior of narrow channels, or in the 
 parenchyma of the organs, as in the case of Distomum (Bilharzia) 
 hcematoHum. The venous branches underlying the mucous membrane 
 of the ureter in which this worm deposits its ova cause, through the 
 
 1 Gb'ze tells (" Verauch einer Naturgesch., u. s. w.," p. 234) of "a very lean and 
 wretched looking " rat, of which the liver was so much riddled with Cysticerci that, " on 
 account of the great number of bladders, hardly any of the tissue could be seen. " Another 
 very similar case is also given, loc. cit. p. 243. 
 
 2 In this way the bile ducts of the rabbits are changed into more or less closed cysta, 
 through the influence of the continuously developing and multiplying Psorospermiae. A 
 similar result may be observed in the LieberkUhnian glands of frogs, when infested by 
 Nematodes and other parasites. According to Waldenburg (Mailer's Arckiv f. Anat. u. 
 Physiol., p. 195, 1862), the blood-vessels of the frog occasionally become worm-cysts, 
 through aneurismal distention and sacculation. 
 
 3 Hence earlier observers thought the seat of the worm was in the interior of the 
 kidney. 
 
 * See Vol. II. ; also Leuckart, " Untersuchungen uber Trichina spiralis," 2d Ed., p. 53. 
 
PATHOLOGICAL EFFECTS OF PRESSURE. 
 
 129 
 
 pressure of the foreign bodies which they contain, a more or less con- 
 siderable hypertrophy in the surrounding tissue, and ultimately be- 
 
 FIG. 76. Kidney of Nasua socialis, with 
 Ewtrongylus in the distended pelvis. 
 
 FIG. 77. Muscle- Trichlrtce, seven weeks 
 old, in the distended sarcolemma- 
 sheaths. 
 
 come so much altered, that haemorrhage ensues, and they discharge 
 their contents into the urinary passages. Similarly an active multi- 
 plication of cells has been observed to take place within the space where 
 ova have been deposited by the Strongylidse of the lung, 1 and round 
 about the so-called " Psorospermiae " (Coccidium, Leuckart), which have 
 wandered into the epithelium. But the cells which are inhabited by 
 the Psorospermise themselves are destroyed by the growth of the latter. 
 
 Such changes have, of course, an effect upon the functions of 
 the infected organs. More or less serious disturbances arise, which 
 affect the general health in various ways, according to their inten- 
 sity, and the physiological importance of the invaded organ. 
 
 The parasitism of Distomum Ticematobium is followed by haema- 
 turia, and parasites in the brain give rise to imbecility, paralysis, 
 madness, or convulsions, according to their situation. 2 Similarly, the 
 
 1 Bellinger, " Zur Kenntniss der desquamativen und kasigen Pneumonic," Archiv fur 
 exper. Pathologic u. Pharm., Bd. i., 1873. 
 
 2 A very familiar example of this is afforded by sheep suffering from the disease called 
 " staggers," caused by Coenurus in the brain. (See Numan, " Over den Veelkop-Blaas- 
 vorm der Hersenen," Verhandl. koninTd. Nederl. Inst. Wetensch. [3], Bd. iii., p. 225, 
 ] 850). The pressure exerted by the Coenurus is often so great that, if the worm be in 
 a peripheral position, even the bones become absorbed, and the neighbouring parts of the, 
 skull become quite flexible. 
 
 I 
 
130 
 
 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 FIG. 78. Ureter, with ex- 
 crescences due to the presence 
 of Uietomum. 
 
 Echinococcus of the liver and the Strongylus of the kidney affect tissue 
 metabolism by suppressing the biliary and urinary secretions ; and 
 the Trichinae, by extensive destruction of 
 muscular tissue, occasion more or less com- 
 plete paralysis. This paralysis disappears 
 some time after the infection, on account 
 of a new formation of the muscular tissue, 
 but no such renewal takes place after the 
 destruction of liver or brain tissue, so that 
 there the functional deviations are permanent, 
 and often increase to such a degree that death 
 is inevitable. It is true that in such cases the 
 death of the host is not always the direct con- 
 sequence of the first operations of the parasites, 
 but often results from secondary disturbances ; 
 and among these, besides the cachexial and 
 dropsical conditions often arising in the course 
 of time from chronic ailments, the slow 
 inflammations and dissolutions brought about 
 by the irregular circulation, caused by the 
 pressure on the larger blood-vessels, ought specially to be noted. 
 
 Fortunately cases of this description are rare. Most of the paren- 
 chyma-worms exert a less dangerous influence, and many, such as the 
 Cysticercus cellulosce of the muscles, cause hardly any disturbance. 
 The result always depends upon circumstances, or, in other words, 
 in such a case as the present, upon the amount of pressure exerted and 
 the physiological importance of the affected organ. Thus the specific 
 nature of the parasite is quite irrelevant, so that Cysticercus cellulosce, 
 for example, which we have just described as harmless when inhabiting 
 the muscles, becomes a most dangerous parasite under certain circum- 
 stances and in certain situations, as in the brain or in the eye. 
 
 In wide spaces, where the parasites multiply into larger masses, 
 their influence consists not so much in pressure as in a more or less 
 complete obstruction of the passages. The influence of this obstruction 
 on the health again depends principally on the relative importance 
 of the organ in the economy of the organism. Thus the occurrence 
 of Cysticercus in the anterior chamber of the eye, or in the vitreous 
 humour, causes blindness. Similarly the aggregation of masses of 
 worms (Stronrjylus s. Ryngamm trachealis) in the windpipe of birds, 
 and especially of our common fowls, often causes suffocation ; and the 
 intertwining of tape-worms and thread-worms in the human intestines 
 produces conditions which have a great resemblance to intussusception 
 of the intestine, or to strangulated hernia. If the interruption be not 
 
WORM-ANEURISMS. 
 
 131 
 
 so complete, the conditions produced naturally differ ; but even when 
 less serious, they often become fatal to the host through long con- 
 tinuance. 
 
 Perhaps it is well at this stage to note the so-called " worm-aneur- 
 isms," which are of such frequent occurrence in the mesenteric arteries 
 (especially the anterior) of the horse 
 that they can hardly be sought for 
 in vain (according to Bollinger, only 
 in 6 to 10 per cent.). There can 
 be no doubt that these formations 
 are caused by the parasitism of 
 Strongylus s. Sclerostomum equinum, 
 which, when quite small (p. 64), 
 enters the intestinal canal of the 
 horse from outside, but soon migrates 
 thence into the circulatory system, 
 and there gives rise to the formation 
 of aneurismal sacs. The manner 
 in which these aneurisms (Fig. 79) 
 are gradually developed cannot be 
 determined in the absence of the 
 necessary data, but the general sup- 
 position is, that as soon as the worms 
 reach the blood-vessels, they begin 
 
 to bore into the arterial coats, FIG. 79. Worm aneurism of the horse. 
 
 and thereby cause a swelling and 
 
 loosening of the walls, so that the lumen of the vessel is con- 
 stricted, and the aneurismal enlargement produced. 1 It is true that 
 afterwards the worms, which have now attained a length of 18 mm., 
 are found chiefly among the masses of albumen in the aneurismal 
 sac, but this situation is probably a secondary one. In some cases 
 new aneurisms are formed in other parts by the wandering thither of 
 the larger worms. That the existence of these aneurisms must 
 often be followed by other diseases is very evident, from the fact that 
 the anterior mesenteric artery in which they are usually situated is 
 the source of blood for a long portion of the intestine, not less 
 than 26 to 27 metres in length. It has indeed been proved by the 
 researches of Bolliuger 2 that the so-called colic of horses, which is 
 
 1 The supposition that the worms give rise to the aneurisms by means of their oral 
 armature, rests upon complete ignorance of the circumstances of the case, since this oral 
 armature is developed only shortly before the arrival of the parasites in the intestine 
 that is to say, when the pathological changes of the artery have long before been com- 
 pleted. See Vol. II. 
 
 3 Bollinger, " Die Kolik der Pferde :" MUnchen, 1870. 
 
132 THE EFFECTS OF PARASITES OX THEIR HOSTS. 
 
 so frequently fatal, is referable in most cases to embolic and throm- 
 botic processes produced by worm-aneurisms. 
 
 Echinococcus may also give rise to emboli, especially when it per- 
 forates any of the larger venous branches, and empties its contents 
 into them. The intruding bladders then generally obstruct the pul- 
 monary artery, so that death rapidly ensues. 
 
 We have hitherto been considering only those influences of 
 parasites on their hosts which are associated with their presence and 
 growth. Very similar symptoms may occur under corresponding 
 circumstances without the intervention of parasites ; for instance, by 
 the growth of tumours. Parasites, however, not only grow, but, with 
 few exceptions, move, and this mobility, which distinguishes them so 
 strikingly from neoplastic formations, becomes another source of 
 manifold mischief to the harbouring organism. 
 
 Having already noted how the effects of the parasites differ 
 according to their situation, size, and stage of development, it is 
 easy to see at once that the disturbances caused by this mobility 
 must be very various. It is evident, for instance, that the effects 
 produced on the host must be very different when the parasites move 
 about within a spacious abode, from those observed when they leave 
 it, and wander through the body. The effects of these movements and 
 wanderings also depend largely on the number and size of the animals, 
 and upon the slowness or rapidity with which they are accomplished. 
 We shall therefore next consider the modifications produced in the 
 organism by the wanderings of the parasite within the body of the host. 
 
 The case of the embryos first demands discussion. They are the 
 most frequent wanderers of all, and, on account of their microscopic 
 size, the most hidden ; so that, without knowledge 
 of their previous introduction, it is difficult to prove 
 them to be the causes of disease. Such being the 
 case, it is easy to see that their influence upon the 
 host can be estimated in the first place only from 
 the results of experiment. According to these, 
 
 FIG. 80. Embryo , , P , , 
 
 of Tcenia. however, the effects have been found to be very 
 
 far from trivial supposing, of course, that the 
 number of wandering embryos is not inconsiderable. 
 
 For the purpose of introducing bladder-worms into Mammalia, I 
 have been accustomed to feed several animals, and especially rabbits ; l 
 and in such cases it has often happened that the animal died in the 
 course of the first few days, or even of the first twenty-four hours, 
 without any obvious external cause. Since in such cases large quan- 
 tities of the eggs of the tape-worm had been administered among 
 
 1 "Blasenbandwiirmer," p. 45. 
 
PARASITES AS MOVING FOREIGN BODIES. 133 
 
 the food, it is likely that death was caused by the wanderings of 
 the embryos. In examining the carcase, the capillaries of the viscera 
 were found considerably injected, especially in the lungs and liver, 
 and sometimes even ecchymosis had resulted. The blood is also some- 
 what thin, but there are no other symptoms of any specific disease. 
 Whether it may be supposed that the embryos (Fig. 80) have caused 
 a capillary embolism in these organs by their wandering en masse 
 into the circulatory system, I cannot decide, although I have suc- 
 ceeded in finding single embryos in the blood of the portal vein. 
 
 Similar cases have been observed by other investigators, 1 and one 
 which Leisering describes, of a lamb fed with Tcenia marginata 
 (e Cysticerco tenuicolli), may be given here. 2 The principal changes 
 in this animal, which died on the fifth day after feeding, were to be 
 seen in the liver, which was congested throughout its whole extent, 
 and traversed by enlargements of the portal capillaries, distended with 
 blood, in which hundreds of small but yet visible tape- worm em- 
 bryos were to be observed. Icterus and extravasations were also 
 noticed, the latter even in the lungs. 
 
 It cannot be doubted that these were the results of the infection, 
 although perhaps the direct cause of death cannot be established with 
 certainty. 
 
 In cases in which the animals under experiment manage to 
 survive the immediate consequences of the infection, and especially 
 in cattle fed with Tcenia saginata, a state is often produced, which 
 in pathological and pathologico-anatomical respects has the greatest 
 resemblance to miliary tuberculosis, and hence has been called by 
 me " acute Cestodic tuberculosis." 3 
 
 The Cestodes are not, however, the only parasites which influence 
 their hosts by the wandering of their embryos. The movements of 
 chose of Trichinae have also an influence ; for the painful sensation of 
 muscular exhaustion, which is felt even in the first days of trichinosis, 
 and rapidly increases in intensity, the inflammation and cedematous 
 swelling of the affected parts, and the restlessness and incipient fever, 
 are all undoubtedly due in great measure to the condition of irritation 
 produced by the wandering embryos. It must, however, be borne in 
 mind, in considering the symptoms accompanying trichinosis, that 
 this disease is the product of a whole series of helminthological con- 
 ditions which run their course side by side in the same host, and 
 
 1 See especially Raum, " Beitrage zur Entwickelungsgeschichte der Cysticercen :" 
 Dorpat Inaug. Dissert., 1883. 
 
 2 Bericht uber das Veterinarwcsen Sachsens, p. 22, 1857-58. 
 
 3 Hosier, ' ' Helniinthologische Studien und Beobachtungen," Berlin, pp. 1 et seq , 
 1864. 
 
134 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 crowd themselves into so short a space of time that it is difficult to 
 determine the effects of the individual factors. After a. more copious 
 infection in the case of pigs and rabbits, a more or less conspicuous 
 reddening of the peritoneal covering of the intestine and the ab- 
 dominal walls may often be observed within the second week, and 
 sometimes even a matting together of the viscera, or a serous effusion 
 into the body-cavity. All these phenomena, although not hitherto 
 observed in man, can only be produced by embryonic wanderings. 
 Virchow is of opinion that the typhoid conditions which accompany 
 trichinosis may also be explained as the direct consequences of the 
 wandering, but perhaps it would be nearer the truth to refer them to 
 the absorption of the waste products, which are produced in masses by 
 the destruction of the muscular tissue. It appears to me very doubt- 
 ful whether the Trichina-embryos have any influence, as is supposed, 1 
 in virtue of certain inherent chemical properties. 
 
 Filaria Medinensis has also sometimes been accredited with 
 poisonous properties, in order to explain the dangerous results which 
 follow the tearing out of the worm ; but it has been shown by the 
 researches of Bottcher 2 that these symptoms are caused merely by 
 the wandering of the embryos in countless numbers into the sur- 
 rounding tissues, and that they are mainly of an inflammatory nature. 
 
 Similarly the embryos of Stronyylus filaria hatched in the lungs 
 of sheep and other ruminants frequently occasion a more or less ex- 
 tensive inflammation, which only ends favourably if the parasite 
 obtain an exit. Very different from such general inflammations are 
 the changes caused by the invasion of the embryos of Ollulanus* 
 which occur in the neighbourhood of each individual worm, and again 
 present all the appearances of a miliary tuberculosis, and are no less 
 dangerous than the Cestodic tuberculosis just mentioned. 
 
 Further, it is not so much the wanderings that act as causes of 
 disease, as the irritations and injuries produced by them. This is most 
 strikingly proved by the history of the so-called Filaria sanyuinis (p. 
 50), which sometimes circulates in millions in the blood of its host, 
 yet only causes disturbances when it gives rise to haemorrhage in 
 making its exit into the cellular tissue, or through the kidney, where 
 it perforates the capillary tuft of the Malpighian body. The haema- 
 turia or chyluria which is caused in this way, and also that resulting 
 from the operations of Distomum, if of long continuance, are followed 
 by anoemic conditions, but this is generally the only expression of the 
 helminthiasis. 
 
 1 Friedreich, Deutsckes Arckiv f. klin. Med., p. 265, 1872. Huber is of the same 
 opinion in regard to Ascaris lumbricoides, Ibid. p. 450, 1870. 
 8 Sitzunysb. der Dorpater NuturforscJiergesellsch., p. 275, 1871. 
 ' See Bugnion and Stirling at the places mentioned on p. 47. 
 
EFFECTS OF WANDERING EMBRYOS. 
 
 135 
 
 It is only in rare cases, according to Lewis, that the Hsernatozoa 
 give rise to more or less serious disturbances in other organs through 
 ruptures or capillary embolism. Gruby and Delafond have observed 
 epileptic fits in dogs infected with these parasites. 1 
 
 When the embryos have finished their wandering, and have settled 
 down and begin to grow, new phenomena appear in place of the 
 former ones, and are of greater or less importance according to circum- 
 stances. They have generally the character of local inflammatory 
 affections, the causes of which are naturally found in the combination 
 of the commencing pressure with the still slowly progressing motion. 2 
 The serious extent to which these inflammations may increase is 
 shown not only by the instance we have given of acute Cestodic tuber- 
 culosis in the ox, but also by the constancy with which our experi- 
 ments with Ccenurus produced in three weeks an inflammation in the 
 brain of the sheep, which was usually fatal. 3 When the skull is opened 
 in such cases, streaks of caseous exudation, about an inch in length, 
 are seen on the surface of the brain (Fig. 81), marking out the path 
 of the parasites and identified by the character of their surroundings 
 as the centres of the inflammatory processes (Haubner, Leuckart, 
 van Beneden). 
 
 FIG. 81. Brain of a lamb with tracks of Crenurus. 
 
 These local phenomena are of course not equally dangerous in all 
 organs. I have frequently seen the livers of rabbits which had been 
 fed with Tcenia serrata crossed and riddled by hundreds of young 
 Cysticerci (Fig. 82, see also p. 70), and yet I do not remember a single 
 case of death resulting from these disturbances. 4 As soon as the 
 worms have slowly wandered out of the liver, that is to say in the 
 
 1 Comptes rendiis, t. xxxiv., p. 9, 1852. 
 
 a There is no doubt that the continuous pressure of the growing worm often of itself 
 gives rise to inflammatory processes ; so that it is sometimes impossible sharply to 
 distinguish the effects of simple pressure from those caused by the motion of the parasites. 
 
 3 This inflammation of the brain is somewhat incorrectly called " staggers " by some 
 investigators, but the characteristic symptoms of the latter disease do not appear until 
 some months after infection. 
 
 * Compare with this the plates in my work " Blasenbandwurmer," p. 124, Part i., 
 Figs. 1-3. 
 
136 THE EFFECTS OF PARASITES OX THEIR HOSTS. 
 
 third or fourth week after they have been administered to the animal, 
 the passages which they have made close up. The former congested 
 condition then ceases, the exuded material which, along with the 
 worms, had blocked the passages is reabsorbed, and a healthy appear- 
 ance returns. Only the persisting scars betray the former state of the 
 organ. 
 
 I have found it to be the same in the case of Cysticercus tenui- 
 collis, except that, as this is of larger size at the time of its exit, it may 
 under similar circumstances produce more serious effects. In livers 
 
 FIG. 83. Exit of a young 
 Cyaticercua tenuiroUis from the 
 liver. 
 
 FIG. 82. A piece of the liver of the rabbit with 
 perforations caused by bladder- worm (Cysticercu* 
 pisiformi*). 
 
 which had just been left by these parasites, I have seen holes so long 
 that the finger could be inserted nearly half-an-inch. The healthy 
 state of my animals is explained by the fact that the number of para- 
 sites was not very large, never indeed above twelve. The emigration 
 of a greater number produces not seldom, however, fatal effects. 
 
 Much more dangerous are the consequences of the repeated wander- 
 ings of Pentostomum denticulatum (see p. 77) from the liver and lungs. 
 In order to understand this, it is only necessary to see the rapid and 
 powerful leech-like motions of the animal and its armature, consisting of 
 circles of hard bristles and the powerful hooks (Fig. 56). After a 
 copious infection, the liver and lungs are perforated in all directions, 
 and their surfaces are covered with holes (Fig. 84), each of which 
 forms the centre of a more or less extensive inflammatory circle. 
 This is especially the case in the lungs, which are often greatly dis- 
 tended by infiltration of blood and exuded fluids. When the Penta- 
 stoma migrate in larger numbers into the cavity of the body, these 
 symptoms are usually accompanied by peritonitis, which frequently 
 terminates fatally. x Even cases of natural infection may be followed 
 by fatal results, as is proved by the instance which Weinland gives of 
 
 A Leuckart, "Bau und Entwicklungsgesch. von Pentastomum tsenioides," p. 14, 
 Leipzig, 1865. 
 
WANDEHING OF CYSTICERCUS AND PENTASTOMUM. 
 
 137 
 
 an Antilope bubalis which succumbed to Pentastomum denticulatum.* 
 Still we have not yet observed any case of Pentastomum becoming 
 dangerous to man. This is probably due to the fact that as the usual 
 mode of transference is the smelling and licking of the hands by dogs, it 
 is imported singly or in very small numbers. Pentastomum constrictum 
 (Fig. 85 A), which infests man in the tropical regions of Africa, seems 
 on the other hand to have a much more intense influence on its host, for 
 
 FIG. 84. Lung of a rabbit infected 
 with Pentastomum. 
 
 FIG. 85. Pentastomum constrictum; A, 
 twice natural size; B, liver (after Aitken); 
 (?, in the lung. 
 
 according to the information furnished by Aitken 2 in regard to a few 
 cases of this kind, the exit of this parasite from the liver and lungs 
 frequently causes death. 3 It must, of course, be remembered that 
 while the length of P. denticulatum is hardly a centimetre that of P. 
 constrictum is nearly seven. 
 
 We have hitherto considered only those wanderings which occur 
 constantly and regularly in certain parasites, and sooner or later in 
 their developmental life. The number of cases cited would have been 
 greater if we had not turned our attention exclusively to the higher 
 animals. Otherwise, we should have mentioned the almost always 
 fatal wanderings of the parasitic larvae of various insects and Filarice 
 (Gordius, Mermis). 4 ' But without these, the account which has been 
 
 1 Der zoologische Garten, p. 2, 1860. 
 
 2 On the occurrence of Pentastomum constrictum in the human body as a cause of pain- 
 ful disease and death : Aitken, " The Science and Practice of Medicine," 4th ed., 1866. 
 
 3 Wedl (Sitzungsb. d. k. Akad. Wiss. Wien, Bd. xlviii., p. 408, 1863) mentions a 
 similar case of a lioness which contained a large-sized Pentastomum (P. moniliformel) in 
 its liver and spleen. 
 
 4 Of the other cases belonging to this class, I shall only cite an observation made by 
 Busch ( " Beobachtungen uber Anatomic und Entwicklung wirbelloser Seethiere," p. 98, 
 Berlin, 1851) regarding a small asexual Nematode, which perforates the tissues of the 
 
138 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 given is sufficient to establish the pathological importance of these 
 phenomena. 
 
 Besides the constant and regular wanderings of the larvae, there 
 are similar movements associated with the full-grown animals, but 
 these are, as a rule, only occasional and fortuitous. Among them we 
 class those of Ascaris into the body -cavity, which, of course, pre- 
 suppose perforation of the alimentary canal. 
 
 The possibility of such perforations has been much questioned, 
 both in earlier and more recent times, because the thread-worms are 
 without any kind of boring apparatus. It has also been attempted to 
 explain the numerous cases of this kind mentioned in literature by 
 the supposition that the worms play only a secondary part, since they 
 have been observed, perhaps after the death of the host, to make use 
 in their movements of passages caused by ulcers perforating the in- 
 testine. In proof of the correctness of this hypothesis the character of 
 the perforation has been cited, which seems to be the result rather of 
 a gradual erosion than of a mechanical force. 
 
 Although it is difficult to decide the question with certainty, I 
 think that the denial of the presence of these perforations is quite 
 unfounded. 1 That a boring apparatus is by no means necessary for 
 the perforation of tissues and organs has been decided by modern 
 investigations, and is indeed sufficiently proved by the instances which 
 we have collected of wandering Cysticerci. When we consider the 
 size of these thread-worms, it is, however, evident that they cannot 
 perforate the walls of the intestine with the same ease as the embryos 
 of Trichina. If the boring of the latter be described as an " acute " 
 process, that of Ascaris might be termed " chronic," since it is 
 accomplished by means of a continuous pressure of the head against 
 the wall, a process perhaps resulting not directly in a perforation, but, 
 in the first place, only in certain structural changes in the tissue, 
 which then in turn make the perforation possible. 
 
 In some cases the perforation is not confined to the wall of the 
 intestine. At the umbilicus, and in the inguinal regions, where the 
 abdominal wall yields more easily to pressure, not only the intestine 
 but also the body-wall is perforated. In consequence of the pressure 
 exerted by the parasite, the so-called " worm -abscesses " arise, and 
 inflammation of the connective tissue, which is eventually followed by 
 ulceration, exactly as in the case of the perforations due to Filaria 
 Medinensis. 
 
 Sagittce indiscriminately in all directions. " The poor Sagittal," he says, " of course 
 suffer terribly when the invaders begin their wanderings, and generally die in a tetanic 
 condition, with the hooks stretched out stiffly from the head, and the body bent rigidly 
 backwards." 
 
 1 See VoL II. 
 
WANDERINGS OF ECHINORHYNCHUS AND ITCH-MITES. 139 
 
 It is self-evident that the consequences of such boring out of or 
 into the body-cavity must be much more deep-seated and dangerous 
 than those which result from the mere wandering of an embryo. The 
 size and very appreciable movements of the parasite usually produce 
 in man a very intense peritonitis, which has a specially rapid and 
 fatal course in those cases in which other foreign substances have 
 passed through the walls of the intestine along with the worms. 
 
 Thread-worms, however, are not the only intestinal worms which 
 are capable of such migrations. These are even more frequently 
 undertaken by the Acanthocephali, which, with their powerful hooks 
 studding the sides of a retractile proboscis, are specially adapted for 
 such work. Even the Echinorhynchus gigas of the pig, although 
 several millimetres in diameter, can by means of its boring ap- 
 paratus perforate the walls of the intestine. We know also of similar 
 wanderings, even among the tape-worms not only in the case of Tcenia 
 solium, but also of other species not provided with hooks. Thus Tcenia 
 plicata not unfrequently passes from the alimentary tract of the hare 
 or rabbit to the body-cavity, without, however, exciting the usual 
 serious symptoms, since these hosts are but slightly liable to peri- 
 tonitis. Goze found in one case 1 " a small aperture closed by thick- 
 ened margins, by which the worms had made their exit, and which 
 could only be observed internally on the villous surface." He further 
 cites the case of a diver infested with Ligula, some of which had 
 penetrated the intestinal walls. 2 In its larval state the Ligula, as 
 is well known, inhabits the body-cavity of white-fish, especially of the 
 bream, and towards the end of August it often breaks through the 
 body -wall "ventrally, laterally, or dorsally, or even sometimes 
 on the head or near the tail. The point where the perforation has 
 taken place is somewhat swollen, the skin becomes thin, and the 
 blood-covered wound which is left is longitudinal, like that of an 
 artery." 3 Steenstrup observed a similar phenomenon in the Schisto- 
 cephalus of the stickleback, but in this case the injury generally 
 proved fatal.* 
 
 In contrast to these only occasional wanderers, there are also 
 adult parasites which are continually moving. Chief among these is 
 the itch-mite (Sarcoptes scabiei), which burrows in all directions ill 
 the epidermis (Figs. 86 and 87), and by the perforation of the papillae 
 of the cutis causes the painful eruptions which were for many 
 centuries considered as a special disease the itch. 
 
 1 " Versuch einer Naturgesch., u.s.w.," p. 367. 
 
 2 Ibid., p. 25 and p. 185. 
 
 3 Bloch, " Abhandl. u. s. w.," p. 2. 
 
 * See the observations cited on page 25, and also v. Baer, " Ueber Linnes im 
 WasRer gefundene Bandwttrmer," Verhandl. naturf. Freunde Berlin, Bd. i., p. 388, 1829. 
 
140 
 
 THE EFFECTS OF PARASITES OX THEIR HOSTS. 
 
 The species of Filaria which infest the connective tissue of their 
 host are similar in habit to the itch-mites. They have been usually, 
 but erroneously, regarded as quiescent Entozoa, while in reality they 
 are in constant, though slow, motion. And since many nerves 
 and blood-vessels ramify in this connective tissue, it is on a priori 
 grounds probable that these parasites are the cause of many patho- 
 logical phenomena. 1 These will of course vary widely in detail, 
 according to special conditions, but will especially depend on the 
 nature of the organ attacked and the character of the wandering 
 parasite. Thus Filaria Medinensis moving among the muscles gives 
 
 FIG. 86. Sarcoptcs scabiei. 
 
 FIG. 87. Crust of Scabies norvegica, with 
 mites, their borings, eggs, and ex- 
 creta. 
 
 rise usually only to a more or less violent pain, while Filaria loa 2 
 under the conjunction of the eye causes a chronic inflammation, and 
 Filaria Bancrofti, the parent of the Filaria sanguinis (p. 50), discovered 
 by Lewis, inhabiting the sub- epidermal tissue, especially in the in- 
 guinal region, causes sclerotic and lymphatic changes, which have a 
 
 1 Eisig observed a Filaria in the kangaroo, which had bored through the pericardium, 
 and thereby induced a fatal pericarditis. Zeitschr. f. wiss. Zool., p. 99, Bd. xx., 1870. 
 
 8 Through the kindness of Dr. Falkenstein, a member of the German-African ex- 
 pedition, I have had the opportunity of examining a specimen of Filaria loa, and have 
 convinced myself that it is by no means identical with F. Medinensis, but differs widely 
 from that form. The embryos enclosed in thin egg-shells bear a close resemblance to 
 F. sanguinis, but are smaller (0'21 mm.). 
 
IRRITATION DUE TO INTESTINAL WORMS. 141 
 
 certain resemblance to elephantiasis, and have been often regarded 
 as such. 1 
 
 Under such circumstances, it is not surprising to learn that worms 
 by their movements frequently cause disturbance, and often very 
 serious disturbance, in the intestine and other viscera. They excite 
 irritation, which in delicate lining membranes naturally leads to 
 catarrhal and inflammatory states proportionate in intensity to the 
 number and activity of the parasites. 
 
 A striking proof of the correctness of this statement is furnished 
 by the Trichince, which immediately after their introduction give rise 
 to a series of pathological phenomena in the intestine, 2 which, in 
 cases where the parasite is abundant, are so intense that the patient 
 sometimes appears as if attacked by cholera. In rabbits and other 
 small animals death not unfrequently supervenes at this stage. On 
 dissection the intestine is seen to be strongly injected, and the mucous 
 membrane is covered by a thick layer of dead epithelial cells, forming, 
 as it were, a false membrane. In the same way it has been found 
 that the so-called " Cochin-China diarrhoea " (which we had the first 
 opportunity of stiidying closely only a few years ago, through the 
 French soldiers who suffered from it) is determined by a small parasitic 
 thread- worm (Anguillula intestinalis), and its Ehabditiform embryos, 
 which in incredible numbers infest the intestine throughout its whole 
 length, from the stomach downwards, and even fill the ducts of the 
 associated glands. Many thousands of these worms are voided at 
 each stool, while the Trichince, on the contrary, which live between 
 the villi, are but rarely expelled. The voided worms are, however, 
 continuously replaced, and hence a state of anaemia soon ensues ; and 
 it is this which, in spite of the continual diarrhoea, keeps the intes- 
 tine from exhibiting signs of congestion. One of the common thread- 
 worms, the so-called " maw- worm " (Oxyuris vermicularis), also occurs 
 sometimes in great numbers, and then it not unfrequently happens 
 that mucus and even bloody diarrhcetic stools result. 
 
 Nor do thread-worms only occasion such intestinal phenomena 
 when they occur in great numbers, but tape-worms may do so likewise. 
 In proof of this assertion, I may refer to the fact that the intestine of 
 the dog, so generally infested by Tcenia ecliinococcus or T. cucumerina, 
 exhibits, as far as the worms extend, a loosened and reddened mucous 
 
 1 Here we might also cite the case of Stephanurus dentatus ( = Sclerostomum pinguicola), 
 which occurs very abundantly in swine in North America and Australia. It inhabits the 
 fatty masses near the kidneys, and riddles them in all directions, producing cavities filled 
 with pus (see p. 46). The affected swine suffer pretty constantly from paraplegia. 
 
 2 The existence of these intestinal affections was for a while emphatically disputed by 
 Virchow, Knoch, Zenker, and others, until the epidemics at Hettstadt, and especially 
 at Htdersleben, established my observations beyond cavil. 
 
142 THE EFFECTS OF PARASITES OX THEIR HOSTS. 
 
 membrane ; and these structural changes cannot be without correlative 
 influence on the intestines. I have further established by experiment 
 that tape- worms may under some circumstances prove fatal. I fed a dog 
 with about 150 pieces of immature Tcenia ccenurus, each piece about a 
 span long, and forming altogether a bolus about the size of a goose's 
 egg. This I thrust into the animal's pharynx, beyond the root of 
 the tongue, in the hope that these worms would at least partially 
 develop further in their new host. This did not happen, for eighteen 
 hours after the feeding the powerful dog was a carcase. On exa- 
 mination, the stomach and duodenum were found to be filled with 
 a bloody fluid. The walls were very strongly injected, covered 
 with abundant ecchymoses, and partly with a loose layer of altered 
 epithelial cells. The same phenomena, in a less conspicuous degree, 
 could be traced to about the middle of the small intestine. The 
 tape-worms were entirely digested, but traces of them were dis- 
 coverable here and there in the small intestine ; yet I do not doubt 
 that they were to blame for the death of the dog, and would hazard 
 the suggestion that this was due to the rapid and violent movements 
 of the worms in their endeavour to escape the fatal action of the 
 digestive juices. At any rate, the common supposition that tape- 
 worms are among the slowest and most indolent of organisms is 
 certainly erroneous, as any one may satisfy himself by observing them 
 in their natural environment, the warm intestine, or even in a 
 hatching apparatus. 
 
 But the presence of a great number of intestinal worms is by no 
 means a necessary antecedent to such pathological changes. Even a 
 single tape-worm or Ascaris can determine a more or less intense in- 
 testinal irritation, provided only that it be habitually characterised by 
 a somewhat vigorous motion. I have frequently observed a reddening 
 and loosening of the mucous membrane, like that we have cited as 
 produced by Tcenia echinococcus and T. cucumerina, in cases where 
 only a single large tape-worm or thread-worm was present, and the 
 pathological condition was so strictly limited to the area occupied by 
 the parasite that there could be no doubt as to the causal relation. l 
 Since the dissection was made immediately after death, the result 
 could be no post mortem phenomenon, but could only be referred to 
 the movements of the living worm. 
 
 A state of intense inflammation is sometimes excited by parasitic 
 
 1 Here might be quoted the following observation of Gb'ze (see loc. cit., p. 71) : 
 "My child suddenly died on the llth February 1778, and on post mortem exam- 
 ination on the following day there was found in the intestine, not far from the stomach, 
 a large thread-worm, which had caused a red inflammatory spot at the place where it 
 had lain." 
 
IRRITATION DUE TO INSECT-LARVAE. 
 
 143 
 
 insect larvae. 1 The symptoms of such states vary according to 
 the condition and individuality of the patient, but the most frequent 
 are disturbances of some sort in the digestive function, or perhaps the 
 colic-like pains consequent upon these. The presence of larvse of 
 Anthomyia sometimes results in symptoms not unlike those of cholera. 
 In many cases the phenomena are further complicated by the irrita- 
 tion of the sympathetic and reflex systems of 
 nerves, and thus arise convulsions sometimes 
 local, sometimes general St. Yitus' dance, and 
 similar troubles. Many exaggerated statements 
 may have been made upon this matter, but we 
 have no right on that account to deny the exis- 
 tence of a relation which numerous observations 
 have made in the highest degree probable, and 
 which involves no inconsistency with anything 
 that we know of the nature of these diseases. 2 
 
 What has been said here of intestinal worms 
 is also essentially true of the inmates of other 
 organs. Congestion and inflammation, with 
 their manifold secondary consequences, are ever 
 the first results of the irritation caused by the 
 various parasites. FIG. 88. Larva of A ntho- 
 
 A most familiar example is furnished by the myia cuniculari8 ' 
 species of Strongylus which often occur in great numbers in the 
 bronchi of ungulates (S. micrurus and S. rufescens in the ox, 
 S. filaria in the sheep, S. paradoxes in the pig). These excite 
 inflammation, which spreads rapidly from the affected bronchi 
 to the associated pulmonary tissue, and often ends fatally. Fila- 
 roides mustelarum (= Spiroptera nasicola, Leuckart), living in the 
 frontal sinuses, causes the absorption of the walls outwards to 
 
 1 Of the numerous relevant observations I will only cite one : Meschede, " Fall von 
 plotzlicher schwerer Erkrankung durch verschluckte Fliegenmaden." Virchow's Archiv 
 f.pathol. Anat., Bd. xxvi., p. 300, 1866. 
 
 2 I may take this opportunity of citing the " odd observation " which Goze (loc. cit., p. 
 27, note) made on a young dog, hardly one year old, which suffered from Tcenia cucumerina. 
 " He was often seized with cramp, caused probably by the number of the worms, and lay 
 with his head and back bent, and the belly uppermost. He bent often to the side, and 
 rolled himself on the sand, but during the whole period of two months that I watched 
 him I never heard him bark once. I then administered a drastic purgative, which led to 
 the expulsion of a whole bowl of tape-worms, with and without ' heads.' He was restored 
 to health, and began to bark next day. Are there not instances of children infested with 
 worms remaining deaf and dumb for years ? I recall at least the title of a disserta- 
 tion ' De aphonia ex vermibus.'" Similarly Leisering remarks, on the strength of his 
 own observation, that dogs much infested with Tcenia echinococcus not unfrequently suffer 
 from a disease exactly like hydrophobia in its external characters (Bericht Veterinarwcsen 
 Sachsens, Jahrg. x., p. 87, 1864). 
 
144 
 
 THE EFFECTS OF PARASITES OX THEIR HOSTS. 
 
 the periosteum, and thus riddles the skull. 1 Similarly, Pentas- 
 tomum tcenioides, parasitic in the nasal cavity of the dog, occasions 
 after some time (according to Chabert) distinct caries. In recently 
 infected animals an injection and loosening of the Schneiderian mem- 
 brane is all that can be observed. The effect of Pentastomum upon 
 the lungs is much more serious. I have already mentioned how, in a 
 snake (Naja haje) which I examined, it was evident even to the naked 
 eye that death had resulted from pneumonia caused by Pentastomum. 
 There were numerous inflamed regions in the lungs as large as the 
 palm of the hand, and bearing in their centre a Pentastomum firmly 
 fixed by its booklets. 
 
 Even the horseleech (Hcemopis vorax), in tropical countries, and 
 especially in North Africa, is sometimes the cause of chronic in- 
 flammation in aggravated cases of laryngeal consumption, which 
 occurs when the animal is inadvertently swallowed by man or beast 
 when drinking, and settles in the throat or 
 larynx. Still more acute and serious are the 
 attacks made by the larvae of Musca (Lucilia) 
 hominivorax on the throat and nasal cavities 
 of their unfortunate host. Vercamer, a Belgian 
 army surgeon, reports of a soldier in Mexico 
 that in a short time these animals had, with 
 their oral hooks, eroded the glottis, and so 
 riddled and torn the pillars of the fauces and 
 the soft palate, that they looked " as if they 
 had been stamped by a punch." (van Bene- 
 den.) Even in our own country the physician 
 has often the opportunity of observing the 
 mischief wrought by insect larva?, especially 
 Musca vomitoria (Fig. 89) and Sarcophaga car- 
 naria, parasitic in cases of neglected wounds or 
 blennorrhoea. The abscesses caused in tropical 
 countries, and especially in America, by the 
 gad-fly and chigoe, are worth mentioning as 
 analogous phenomena. 
 
 Perhaps we should also mention here the repeatedly observed case 
 of horses, in which the skin, covered with a herpetic eruption, was 
 literally inhabited by larval Nematodes. 2 Another problematical 
 
 1 See Weijenberg, Archives nterlandaises sci. exact, et not., t. iii., p. 428, 1868. 
 
 8 See cases cited by Rivolta, II medico veterinario Torino, p. 300, 1868 ; or Hering's 
 Repertor. f. ThicrkeUk., Jahrg. xxix., p. 373, and Sommer, Oesterr. Viertdjahrsschrift f. 
 Vcterinarkundc, Bd. xxxiv., p. 183. 
 
 FIG. 89. Larva of Musca 
 vomitoria. (Nat. size and 
 enlarged. ) 
 
DIAGNOSIS OF PARASITIC DISEASES. 145 
 
 case is reported by O'Neill * from the West Coast of Africa, where a 
 skin disease resembling itch occurs among the negroes, and is also 
 attributed to the presence of young Nematodes. I have myself had 
 the opportunity of confirming the existence of such parasites on the 
 skin of a diseased fox, but am still doubtful whether the disease can 
 be called parasitic; and I have been confirmed in this doubt by 
 finding, among the scabs of the eczematous skin of a dog, numerous 
 flea-larvae, which could hardly have produced the eruption, but had 
 probably only taken advantage of it as an abundant source of food. 
 
 Glancing over the various pathological states induced in manifold 
 ways by our unbidden guests, we survey a long catalogue of affections 
 of most varied nature and importance. It is but rarely, however, 
 that they show a combination of features so specific and characteristic 
 that one can at once and with probability decide as to their nature 
 and etiology. On the contrary, the results of parasitism might, in the 
 majority of cases, be referred quite as well to entirely different 
 causes. 
 
 DIAGNOSIS. 
 
 Such being the case, it is evident that a sure diagnosis of helminthic 
 diseases necessitates, in the majority of cases, an objective proof of the 
 existence of the parasites. 
 
 This proof may be furnished in various ways, according to the oc- 
 currence and nature of the parasites. It is most readily forthcoming, 
 if we omit the Epizoa from consideration, in the case of those which 
 inhabit the alimentary canal, or other organs opening to the exterior, 
 not only because the animals frequently pass out of themselves, or are 
 expelled by proper treatment, but also because, with few exceptions, 
 they are sexually mature, and produce eggs in such immense quan- 
 tities that their detection in the excreta by the aid of the microscope 
 is a matter of very little difficulty. The importance of the examina- 
 tion of human excrement has been already emphasised on all hands, 
 especially by Davaine, 2 Lambl, 3 and Vix, 4 and even earlier by 
 Malmsten and others. 
 
 Among the Helminths infesting man there are (including Dochmius) 
 nine species which have to be considered in such examinations : 
 
 Three Cestodes 
 
 Tcenia saginata (Fig. 90, H). 
 
 solium (/). 
 Bothrioceplialus latus (K). 
 
 1 Lancet, Feb. 1878. 8 Prager Vierteljahrsschrift, Bd. i., p. 1, 1859. 
 
 2 M6m. soc. biol, t. iv., p. 188, 1857. * AUgemeine Zeitschr. f. Psychiatric, p. 114, 1860. 
 
 K 
 
146 
 
 THE EFFECTS OF PARASITES OX THEIR HOSTS. 
 
 Two Trematodes 1 
 
 Distomum hepaticum (F). 
 lanceolatum (). 
 
 Four Nematocles 
 
 Ascaris lumbricoides (A). 
 Oxyuris vermicularis (, (7). 
 Trichocephalus dispar (D). 
 Dochmius duodenalis (E]. 
 
 They all produce eggs of such characteristic form and size (see 
 figure), that one can, almost by a mere superficial inspection, refer 
 them to their parent animal. The eggs of the two species of Tcenia 
 
 FIG. 90. Eggs of worms found in the alimentary canal of man. ( x 400.) 
 A, Ascaris lumbricoides; B,C, Oxyuris vermicularis ; D, Trichocephalus dispar ; 
 E, Dochmius duodenalig; F, Distomum hepaticum ; G, Distomum lanceolatum ; H, 
 Tcenia solium; I, Tcenia saginala; K, Eothriocephalus latus. 
 
 are the most difficult to distinguish. They differ almost solely in 
 that those of T. solium are somewhat more spherical, and on the 
 whole smaller, than those of T. saginata. The eggs of Distomum 
 hepaticum are the largest, and indeed gigantic, attaining a size of 
 0135 mm. long by 0*083 mm. broad. They are nearly twice as long 
 as the eggs of Bothriocephalus latus and Ascaris lumbricoides, and 
 
 1 These both live in the gall-ducts, out of which the eggs are only accidentally trans- 
 ferred to the alimentary canal. 
 
MICROSCOPIC EXAMINATION OF EXCRETA. 147 
 
 thrice as long as the others. Like the eggs of Distomum lanceolatum 
 and Bothriocephalus, they bear a small, usually inconspicuous, lid at 
 one end. The eggs of the two species of Tcenia are provided with an 
 extremely thick shell, the more conspicuous since it has a brown 
 colour and distinct radial markings, caused by a covering of closely 
 packed little rods. The eggs of Ascaris lumbricoides and Trichocephalus 
 dispar are also thick-shelled, and the former are further enveloped in 
 an albuminous sheath, usually coloured with bile pigment, while the 
 latter are perforated at the poles and provided with an albuminous plug. 
 The contents of the eggs also vary, being sometimes, indeed usually, 
 unaltered, but sometimes in process of yelk-division (Dochmius), or even 
 already exhibiting an embryo, as in Tcenia solum, T. saginata, and 
 Oxyuris. In the last instance the embryo is only partially developed. 
 We can to a certain extent infer the proportionate number of the 
 different parent parasites from the quantity of eggs expelled from the 
 host, but in so doing we must remember that the fertility of the 
 various forms is by no means equal. And further, the eggs will be 
 more easily and more abundantly found the nearer the parasite is to 
 the anus, for then they will not be indifferently mixed through the 
 faeces, but will be found especially in the outer portion and mucous 
 surroundings. The eggs of Oxyuris are most easily demonstrated. 
 This statement is consistent with the result of Vix, who among 
 his patients affected with Oxyuris never found a single case where 
 the eggs were not to be observed in countless numbers in the first 
 microscopic preparation, or even first field of vision. Vix recom- 
 mends further the examination not of the faeces, but only of the 
 mucus, which can be easily removed from the anus or higher portion 
 of the rectum with the handle of a scalpel or catheter. This method 
 might suffice for Oxyuris, but is less likely to succeed in the case 
 of other parasites which infest higher portions of the alimentary 
 canal, and whose eggs are chiefly found in the faeces themselves. 
 Therefore, in suspected cases of helminthiasis, the faeces ought not 
 to be left unexamined, even when the examination of the mucus yields 
 no positive result. 
 
 We need not further discuss the methods of examination, since 
 these will partly suggest themselves in the course of what is certainly 
 not a very pleasant task. 
 
 It ought, however, to be specially noted that in some established 
 cases of Tcenia the eggs are sought for in vain. This is readily in- 
 telligible when we remember what we have previously (p. 65) men- 
 tioned, that the eggs of these animals are not liberated within the 
 alimentary canal, but reach the exterior still enclosed in the proglottides. 
 The eggs which, in spite of this, are found here and there in the faeces, 
 
148 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 arise from an accidental rupture of the joint, often readily consequent 
 on the contraction of a distended uterus. One does not expect to find 
 eggs of Trichinae on such examination, since, as is well known, the 
 embryos of these worms become free within the body of the parent, 
 and immediately bore througli the walls of the intestine. But, on the 
 other hand, one sometimes finds the mother- Trichinae themselves, 
 though on the whole much less frequently than, judging from the 
 analogy of Ithabditis stercoralis, one would expect from their usually 
 very abundant occurrence in the alimentary canal of the host. To 
 understand this we must remember that the Trichince are enabled by 
 their long, thin form to adhere closely to the intestinal villi, and, thus 
 protected, to escape the pressure of the faeces. 
 
 Balantidium (Paramcecium) coli is, like Rhabditis stercoralis, also 
 to be found in great abundance in the faeces and intestinal mucus both 
 of man and of the pig. In similar fashion evidently we may expect 
 to diagnose Strongylus gigas, Filaria sanguinis, and Distomum hcema- 
 tdbium from the urinary deposits, the species of Strongylus infesting 
 the air passages from the sputum, and Pentastomum tcenioides from 
 the nasal mucus ; and all this has been at least partially established 
 by experiment. 
 
 The inmates of the various organs which open to the exterior are 
 not, however, the only parasites whose presence admits of objective 
 proof. Thus by the simple examination of the tongue, especially of 
 the under surface, it is sometimes possible to affirm the presence both 
 of Trichince 1 and of Cysticercus. 2 Similarly we can, by the use of the 
 opthalmoscope, not only recognise the same inmates in the eye, but 
 determine their position with the greatest accuracy. 3 When the sus- 
 picion of trichinosis is not fully confirmed by the usual methods, we 
 have only to remove a small piece of flesh from the deltoid, or from 
 any other easily accessible muscle, and subject it to microscopic ex- 
 amination. 
 
 Filaria Medinensis presents no peculiar difficulty in diagnosis, 
 especially in the later stages, when the head of the worm has bored 
 through the skin, and when the living brood passes to the exterior 
 along with the secretion of the perforated part. The diagnosis of 
 Cysticerus in the intermuscular connective tissue is less certain, for 
 
 1 This is only possible when the Trichina-c&pB\\\ea are already calcified that is to say, 
 when the infection had occurred some considerable time previously. 
 
 8 Even Aristotle recommends the examination of the tongue in pigs for the diagnosis 
 of bladder-worm disease (" Hist, anim.," lib. viii., cap. 21, N. 3, "A^Xat 5'etVtV ai x a ^^ ffa <-' 
 l> re "yip TTJS "yXcimjs ry, Karqi, i~x ovfft MaXtora ras x<zXdas." 
 
 8 See especially the observations of v. Graff e, Journal f. Ophthalmdoyie, p. 308, 1857. 
 According to a later report ( Verhandl. d. med. Gesettsch. Berlin, p. 96, 1871), v. Graffe 
 has observed more than a hundred cases of bladder-worm in the eye. 
 
ACTION OF ANTHELMINTICS. 149 
 
 the cysts which may be felt through the skin might be mistaken for 
 abscesses or other tumours. In many cases, however, a sufficient and 
 reliable diagnosis may be based on the manner of occurrence and dis- 
 tribution, but only the results of excision and puncture can finally 
 establish the diagnosis, and this corroboration ought never to be dis- 
 pensed with if the detection of the evil is of any use, as, for example, 
 in the case of contemporaneously occurring mental diseases. 
 
 Among the remaining parenchyma-worms it is sometimes possible 
 to distinguish Echinococcus, and that not only when, as occasionally 
 happens, it empties its contents through the lungs or kidneys, or the 
 alimentary canal, but also when it remains quiescent in the form of 
 a closed cyst. A diagnosis may then be established by means of 
 auscultation and percussion. We are thus not only informed of the 
 existence of an encysted tremulous swelling, but by means of the 
 so-called " hydatid sound " are enabled to identify it as a specific 
 formation, and to distinguish it from other dropsical swellings. 
 
 CURE AND PREVENTION. 
 
 After the detection of a parasitic disease there must follow, not 
 only a treatment of the various symptoms, but a realisation of the 
 indicatio causalis ; that is to say, the removal of the parasites whose 
 presence has induced the pathological state. 
 
 The means taken by the physician to attain this end will, of 
 course, vary greatly, according to circumstances, and will not in every 
 instance lead with equal ease to the desired result. In general, the 
 more accessible the organ which the parasite infests, the more hope- 
 fully may success be looked for. 
 
 The simplest problem is evidently the removal of the Epizoa, 
 either directly by mechanical means, or, more thoroughly and con- 
 veniently, by killing them with suitable preparations (mercury, 
 ethereal oils, petroleum, &c.). In general, the inmates of the ali- 
 mentary canal stand next as regards facility of expulsion, although 
 the varied structure of the organs of attachment occasions consider- 
 able differences in matters of detail. These worms are treated with 
 the so-called " anthelmintics," in which our pharmacopeia so richly 
 abounds. Their action is primarily directed either against the worms 
 themselves or upon the walls of the alimentary canal. The majority 
 of specific worm-cures belong to the first class. They operate by 
 killing or stupefying, or in some way unpleasantly affecting, the 
 worms, so as to induce them to wander outwards, while the second 
 class are successful by increasing the peristaltic movements, or by 
 altering the secretions. 
 
150 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 We restrict ourselves here to mere hints, for our knowledge of the 
 real nature of the operations of these anthelmintic remedies is still 
 uncertain and fragmentary. The experiments of Kiichenmeister who 
 (following Eedi's example) brought Ascaris and other intestinal worms 
 into direct contact with certain substances have done, as yet, but 
 little to enlighten us upon this dark subject, though they deserve full 
 recognition as the first attempts made to settle the question in a 
 rational manner. 
 
 In the other vegetative organs, worms can generally be treated 
 only indirectly, by applications which increase the functional activity 
 of the structure affected, and especially increase its secretions. Suc- 
 cess can only be doubtful, though the hope is that the worms will be 
 carried to the exterior with the copiously flowing secretion. It is of 
 course presupposed that the parasites are not of any considerable 
 size ; for, in such a case, an alteration in the functional activity of 
 the surrounding organ could at most induce the inmate to make a 
 spontaneous emigration. 
 
 As to worms occurring in the parenchyma, the healing art can 
 only avail when they occur in superficial organs, and then only opera- 
 tively. Thus, the well-known Filaria Medinensis may be gradually 
 wound out from the sub-epidermal tissue, and the bladder-worm may be 
 extracted from the eye (as has lately been done repeatedly, especially by 
 von Graffe) like cataract. We know, too, of numerous instances where 
 Echinococcus has been removed from the liver and other internal 
 organs by a fortunate operation, such as opening the cyst by means of 
 caustic paste, by the application of electricity after previous puncture, 
 by injection of tincture of iodine or other irritant reagents. On the 
 whole, however, we are comparatively powerless against such para- 
 sites. And the same may be said with regard to the brood of young 
 worms whose wanderings in the body, after boring through the wall 
 of the intestine, we have hardly any means of preventing. Against 
 these prophylaxis is our only security, and on this we may here lay 
 the greatest emphasis, and claim for it more attention than it has yet 
 received. 
 
 But before we can comply with the conditions of the prophylactic 
 method, we must, above all things, know the ways and means by which 
 parasites and their germs are introduced. We must, in other words, 
 study the life-history of the several parasites, for this alone can put us 
 in possession of the desired information. In this connection hel- 
 minthology has still a mighty task before it, for as yet there are but 
 few human Entozoa whose history and fate are perfectly determined. 
 We do not wish to conceal the difficulty of the problem ; it will yet 
 be long before we can boast of a perfect solution. But the end is- 
 
STATISTICS OF OCCURRENCE OF HELMINTHS. 151 
 
 well worth striving for, since it means nothing else than the health 
 and weal of many thousands. This is no exaggeration ; we have 
 already noted the devastation which the Dochmius intestinalis makes 
 among the Fellahs of Egypt, and we know of similar occurrences in 
 other places. According to the report of Schleissner and Thorstensen, 
 a seventh part of the population of Iceland suffer from Echinococcus * 
 and in tropical countries of the old and new world diseases caused by 
 worms are among the most frequent and widely distributed, e.g., tape- 
 worm, dracontiasis, hsematuria, chlorosis, and dysentery. 
 
 ETIOLOGY. 
 
 Our positive results as to the transference of human worm 
 parasites are still unfortunately very far from complete; we must 
 therefore content ourselves to a large extent with suggestions and 
 deductive conclusions. The following remarks, therefore, make no 
 pretension to exhaust the subject, but they nevertheless contain almost 
 all that we are as yet warranted in maintaining. 
 
 We may first summarise in a sentence the chief result of our 
 previous study of parasitic worms, viz., that the great majority of 
 these creatures inhabit different animals in their different stages. If 
 we apply this sentence to those infesting man, we see at once the 
 probability of the conclusion, that we derive a large proportion, and in 
 all likelihood by far the largest proportion, of our parasites from other 
 animals* Specially, then, must those animals be considered with 
 which we come into contact in any way, and, above all, those domestic 
 animals which are used as food. 
 
 1 Echinococcus is widely distributed in Asia and Australia, and is, according to 
 Schleissner, the most frequent of all diseases in Iceland. In 2600 cases of illness men- 
 tioned in the medical reports, 328 were afflicted with Echinococcus in the liver ; and out 
 of 327 private patients, 57. According to Krabbe, these results are not accurate, and by 
 no means applicable to every district of Iceland. (Archiv f. Naturgesch., Jahrg. xxxi., 
 Bd. i., p. 114, 1865.) According to a calculation of Finsen's for the northern part of the 
 island, Krabbe would conclude that only -^ or ^ of the population can be proved to be 
 suffering from Echinococcus. But even this is a very large number. 
 
 2 A complete statistical account of the human Entozoa even of civilised Europe is still 
 a desideratum. An effort has recently been made in this direction, on the basis of clinical 
 dissections, K. Muller, " Statistik menschl. Entozoen : " Erlangen, 1872, based on the 
 results of the autopsies in Erlangen and Dresden ; and H. Gribbohm, " Zur Statistik der 
 menschlichen Entozoen :" Kiel, 1877. From these results we learn that among us Tricho- 
 ccphalus, Oxyuris, and Ascaris are by far the most common Helminths. In Erlangen 
 there were found, among 1755 bodies, 227 with Ascaris (12'9 p. c.), 213 with Oxyuris 
 (12-13 p. c.), 195 with Trichocephalu* (11 '11 p, c.). Among these 138 post mortem exami- 
 nations of insane patients from the asylum are not included, in whom round- worms were 
 always found, sometimes only one species, sometimes several. In Dresden (out of 1939 
 post mortem sections) the numbers were much smaller, Ascaris in 9'1 p. c., Oxyuris in 2'1 
 
152 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 The correctness of this conclusion is indubitably established by 
 experience and by experiment. Other animals furnish us, then, with 
 the largest contingent of our parasitic guests, but they transmit them 
 in very different stages. The parasites which we derive from the 
 animals used in food are adult forms, like the common tape-worm 
 and Trichina. We receive them, however, in a larval state, the tape- 
 worm in the form of the bladder-worm, the Trichina in its encap- 
 suled form among the muscles. Both these common forms are most 
 commonly derived from the pig, while Tcenia saginata is derived from 
 the ox. On the other hand, our household animals mostly furnish us 
 with the eggs or embryos of their parasites, which then attain in us 
 their larval stage. Among the latter class of animals the dog is pre- 
 eminent as the chief bearer of parasites. From him we derive Pen- 
 tastomum denticulatum, Cysticercus tenuicollis, 1 and especially Echino- 
 coccus, which arise when the ripe eggs of his Pentastomum tcenioides, 
 Tcenia marginata, and Tcenia echinococcus respectively are in some 
 way or other smuggled into us. 
 
 The manner of infection varies according to circumstances, and is 
 largely determined by chance. It would be useless toil to recount all 
 the conceivable possibilities, but a few must be noted. The eggs of 
 
 p. c., Trichocephalus in 2'5 p. c. Gribbohm reports for Kiel (out of 1117 examinations), 
 Ascarit in 18 '3 p. c., Oxyuris in 23 '3 p. c., and Trichocephalus in 32*2 p. c. ; and 
 estimates the sum total of sufferers from parasites in all to be 43 '5 p. c. ; and after de- 
 ducting children under half-year, at 49 P 8 (in women, 53 '8 p. c., in children half a year to 
 15 years old 50 p. c., in men 467 p. c. ). The other parasites have only a small per- 
 centage in comparison to the round- worms. Out of 1117 cases Pentastomum denticulatum 
 was found in 12 ; Cysticercus cettulosce 6 times ; Echinococcus, 3 times ; Tcenia saginata, 
 twice ; Tcenia solium and Trichina each once. I add further that among the 3694 post 
 mortem sections reported by Muller there occurred 17 cases of Tcenia solium ; 5 of T. 
 saginata ; 36 of Cysticercus cellulose?, 9 of Echinococcus. (In Gottingen, Forster found, 
 among 639 bodies, 3 with Echinococcus, and 4 with Cysticercus.) According to Daconta 
 (Zeitschrift fur Epidemiologie, Th. i.) there is one tape-worm patient in Thiiringen for 
 every 3315 inhabitants ; in the medical districts of Eisenach, Apolda, Jena, and Weimar, 
 however, there is one for every 486. For the town of Hanover even 2 p. c. of tape-worm 
 patients have been computed. Cruse found in Dorpat Bothriocephalus latus, at 482 post 
 mortem dissections, in 6 p. c. (Dor-pater med. Zeitung, Bd. ii., p. 315), Ascaris lumbricoides 
 in 9'9 p. c. In comparison with these statements, I remark that Krabbe saw in Copen- 
 hagen and the surrounding district, among 500 dogs, 336, that is 67 p. c., infected with 
 Helminths. Atcaris marginata was found in 24 p. c. ; Tcenia marginata in 14 p. c. ; T. 
 cucumerina in 48 p. c. The rest of the Helminths occurred much less often Tcenia 
 cosnurus in 1 p. c. ; T. serrata in 0'2 p. c. ; T. echinococcus in 0'4 p. c. ; Bothriocephalus 
 sp. in 0'2 p. c. ; Dochmius trigonocephalus in 2 p. c. (" Recherches helminthologiques, " 
 p. 3 : Copenhagen, 1866). It was different in Iceland, where Krabbe found, in 100 dogs, 
 Tcenia marginata 75 times ; T. ccenurus 18 times ; T. echinococcus 28 times ; the T. 
 cucumerina 57 times ; T. lagopodis 21 times ; Bothriocephalus 5 times ; and Ascaris 
 marginata only twice. There were only 7 dogs free from parasites in Iceland. Ibid., 
 p. 21. 
 
 1 Krabbe considers the occurrence of Cysticercus tcnuicottis in man as doubtful, 
 Ugeskrift fur Laeger, Bd. xxxvii., No. 5, 1862. 
 
POSSIBILITY OF SELF-INFECTION. 153 
 
 Pentastomum tcenioidcs, reaching the exterior in the nasal mucus, are 
 transferred to us usually when the dog caresses us or licks our hands. 
 They may also find access directly to our food, such as bread and 
 salad, or may be deposited on vessels which we use in eating and 
 drinking. In the same way, and especially by dirty dishes or food, 
 are the eggs and embryos of the dog's tape- worm imported into us, 
 and this is all the easier since the eggs are not voided singly from their 
 host, but enclosed by the joints, which not only have a power of spon- 
 taneous motion, but may, in virtue of the glutinous surface of their 
 body, be carried about in many ways. The eggs of these animals also 
 frequently reach us through the medium of water used for drinking 
 or washing purposes. 
 
 One must not, however, think that the existence of a parasitic 
 larval stage necessarily presupposes an importation from another 
 animal. It sometimes happens that man infects himself. This is 
 indeed constant in the case of Trichina, the embryos of which are, as 
 we know, born free in the intestinal canal of their host, whence they 
 wander without further change into the muscles, there to become the 
 well-known encapsuled worms. Man may also infect himself with 
 embryos of Tcenia solium, if he transfer the ripe joints or the eggs 
 alone into his stomach. I think it impossible, however, that any such 
 self-infection could take place directly in the intestine. This has 
 already been affirmed by Kiichenmeister, but the liberation of the 
 embryo presupposes a removal of the egg- capsule, and, so far as we 
 know, this never occurs before the eggs have passed through the 
 stomach. Experiment further contradicts Kiichenmeister's supposition. 
 In two cases where I succeeded in introducing eggs of Tcenia serrata 
 into the intestine of a young rabbit, by means of a fine syringe intro- 
 duced through an opening in the abdominal wall, the animal re- 
 mained free from bladder- worms. 1 If Kiichenmeister's view were 
 correct, then every one who suffers from tape-worm ought also to 
 suffer from bladder-worm, which, as is well known, is not the case. 
 But if, as often happens, we do find bladder-worms in those who suffer 
 or have suffered from tape-worm, that is because, when a tape-worm 
 is present, the introduction of joints or eggs is obviously an easier 
 matter than when they have to be brought from another man, not to 
 speak of other obvious possibilities, of which I mention merely these 
 that a patient harbouring a tape-worm may in vomiting easily run 
 a risk of transferring some part, or it may be only a few joints, of the 
 worm into his stomach ; and further, that in sleep, when the joints, 
 
 1 This experiment, through which Kiichenmeister still ( ' ' Parasiten, " 2d ed., p. 115, 
 note) looks for the final decision of this question, has been long made by me, indeed 
 fifteen years ago ! 
 
154 THE EFFECTS OF PARASITES OX THEIR HOSTS. 
 
 as not unfrequently happens, issue forth individually and creep about 
 on the body, it may happen that, simply by a wipe of the hand or 
 some other means, they are unconsciously transferred through the 
 mouth to the stomach. 
 
 Encapsuled Trichinae and bladder-worms are not, however, by any 
 means the only Entozoa which man derives from himself. The sup- 
 position of Kuchenmeister, that the Echinococcus also belonged to the 
 number of the " Autochthones " has, however, proved erroneous, for 
 the sufficient reason that the tape-worm, of which it is the immature 
 stage, does not occur in man. 1 On the other hand, we have in 
 Oxyuris vermicularis* a parasite whose transmission very commonly 
 takes place by self-infection. The eggs which under favourable cir- 
 cumstances e.g., a temperature 37'5 C. produce in a few hours a 
 mature embryo, and which are found strewed about in the neigh- 
 bourhood of the infested individual, and often in quantities even on 
 his body, are transferred in various ways, but usually by the hands, 
 to the intestine, and there the embryos escape and rapidly attain 
 sexual maturity. This extreme liability to self-infection, and the 
 continual reproduction of the parasites, are the causes of the persis- 
 tency of 0,r?/ims-disease and of the difficulty of a perfect cure, which 
 is indeed so great that it suggested the possibility of there being eggs 
 which developed directly in the intestine of the host to sexually 
 mature forms. 
 
 Trichocephalus dispar resembles Oxyuris. Davaine believes, 
 however what is not firmly established that the eggs even of 
 Ascaris lumbricoides may, with enclosed embryos, be accidentally 
 introduced into man. The transference is, however, not so direct as 
 in the case of Oxyuris, for between the laying of the eggs and their 
 transference a period of many months usually elapses, during which 
 the eggs have, of course, most diverse fortunes. Nor is it necessary 
 that the eggs be derived from man, for both these worms are found in 
 the pig, though they are then not unfrequently classed as distinct 
 species (Trichocephahis crenatus and Ascaris suillce). 
 
 From these results, we see that we cannot possibly regard our 
 domestic animals as solely responsible for the introduction of the 
 eggs of parasitic worms. We are ourselves partly to blame ; we in- 
 fect our own bodies, and sometimes also those of our fellow-men, just 
 
 1 The opposite opinion rests on a confusion of Tcenia nana, v. Sieb., which is a human 
 parasite, with T. echinococcus, v. Sieb. (7*. nana, van Beneden). The way in which 
 Kuchenmeister uses this confusion (" Parasiten," 2d ed., p. 163, note) as a reproach 
 against me is so strange that I cannot refrain from asking the reader to peruse my harm- 
 less remarks, which have given that author occasion to raise his voice against zoologists 
 (see p. 341 of the first German edition). 
 
 ' See Vol. II. 
 
TRANSFERENCE BETWEEN MAN AND BEAST. 
 
 155 
 
 as do animals with which we are associated. The foregoing remarks 
 have had reference specially to the Entozoa, but these are far from 
 being the only parasites which we derive from our association with 
 other men and animals. It is in fact still more true of the Epizoa, 
 whose transference takes place exclusively in this way. Lice, fleas, 
 mites, find their way to us only through more or less direct contact 
 with other organisms, and may be transferred in all forms, not only as 
 eggs, but also, and that more commonly, in their adult state. 
 
 It is in the highest degree improbable that Entozoa are ever trans- 
 mitted as adult organisms. Klichenmeister has indeed maintained 
 this in regard to Oxyuris, and affirms that it may pass from a man 
 
 FIG. 91. Flesh of pig with bladder- 
 worms (nat. size). 
 
 FIG. 92. Flesh of pig with Trichina:. 
 (x45.) 
 
 to his bedfellow. The supposition has at first sight much probability, 
 for these worms at certain periods, and especially in the evening, 
 issue spontaneously from the anus, and wander round about. I have 
 even seen a patient in whose case the Oxyuris had during a night- 
 sweat ascended as high as the shoulder. 1 But since the transference 
 could only take place per anum, that presupposes circumstances 
 
 1 Michelson describes a case (Berliner Uin. Wochenschrift, No. 33, 1877) in which the 
 Oxyuridcs had occupied the diseased groin of a boy for a dwelling and breeding place. 
 Compare also the observations previously cited (p. 144) as to the occurrence of Nematodes 
 on diseased skin. 
 
156 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 which only exceptionally occur. Further, our deeper insight into 
 the life and developmental history of Oxyuris has rendered Kiichen- 
 meister's supposition, which was never directly proved, somewhat 
 obsolete and gratuitous. 
 
 Although the number of the parasites which we thus derive by 
 external contact from man and beast is by no means a small one, yet 
 it is very considerably exceeded by that contingent which we acquire 
 along with our food and drink. The ox, whose flesh we eat, harbours, 
 as we know, a whole host of young worms (Figs. 91 and 92), which 
 only become mature in the human intestine. From the pig we 
 derive Trichina and Tcenia solium, from the ox Tcenia saginata, just 
 as the cat gets its tape- worm (Tcenia crassicollis) from the mouse, and 
 the mouse its Spiroptera from the meal-worm (Tenebrio molitor). In 
 regard, then, to the helminthological relations of animals, this is the 
 first and most general law, as we have already remarked (p. 80), that 
 the carnivorous animal derives a great part of its Entozoa from its food. 
 But besides the animals actually eaten as food, those also contribute 
 their Entozoa which are accidentally swallowed or carried in some 
 way into the alimentary canal. This mode of introduction (p. 80) 
 obtains among the Herbivora; and of course it is not man only, 
 with his almost equally vegetarian and carnivorous diet, that is 
 subject to these parasites, but even the Carnivora, which avoid vege- 
 table food, are not safe from their accidental importation. 
 
 We shall discuss in the first place the transmission of parasites by 
 the use of flesh as food. 
 
 When flesh is eaten raw, as is the custom in Abyssinia and else- 
 where, the possibility of transference requires no special proof. The 
 worms thus swallowed develop as surely and constantly as in animals 
 under experiment, provided only that they find in their new host 
 the conditions essential for their further development, and that they 
 are not injured by the mechanical processes of eating. It is thus 
 sufficiently evident why Tccnia saginata is found in young and old 
 among the Abyssinians who eat raw beef, and why Europeans are 
 also rapidly infested when they begin to live d V Abyssinienne. 
 
 It is obviously otherwise among civilised peoples, where it is 
 customary to cook the flesh used as food. The danger of infection 
 with the young worms is by this means to some extent lessened, 
 though the protection thereby afforded is only a limited one. 
 
 We may first of all note that, in spite of the general prevalence of 
 the custom of cooking food, there are yet bye-ways open for the intro- 
 duction of parasites. Raw meat is prescribed by the physician in many 
 diseases as a specially nutritious food. During the preparation of 
 certain kinds of food (especially sausages and meat-balls) the raw 
 
INFECTION BY MEANS OF FOOD. 157 
 
 flesh is tasted by the butcher, cook, or housewife, in order to estimate 
 the proper quantity of salt and pepper. Further, in this state it forms 
 the favourite food of many persons, and even whole classes e.g., the 
 workmen in the manufacturing districts of North Germany. It may 
 also happen that we derive parasites from sausage or ham which has 
 come into contact with infected pieces of flesh or with living worms in 
 the butcher's shop. The bladder- worm of the pig, or its ' head/ is often 
 accidentally introduced in this fashion, especially since the butchers, 
 knowing the law against measly flesh, take the greatest care always 
 to cut away and remove the parasites when they appear on the surface. 
 Where the custom of private slaughtering prevails, as in the middle- 
 class families of North Germany, the parasites may be found in the 
 kitchen or store-room, and thus arise many possibilities of trans- 
 ference and importation. One may, of course, urge that a bladder- 
 worm could hardly be overlooked, or inadvertently swallowed, but 
 the ' head ' is enough for the development of the tape- worm, and 
 being easily separable, could not in this state be distinguished from 
 a little lump of fat without close examination. 
 
 Cooking even boiling and roasting is not a constant or sufficient 
 protection against infection. It has indeed been asserted and observed 
 that living intestinal worms (usually Ligula* but sometimes also the 
 so-called Filaria piscium 2 ) are occasionally found in boiled or baked 
 fish. Experiments were made by Pallas 3 and by Bloch, 4 in order to 
 test the truth of this. The worms were cooked some alone and some 
 within their hosts, which are usually small. The results were, however, 
 only doubtful, but it is impossible any longer to doubt the correctness 
 of the statement. By my experiments in 1860, published in the first 
 edition of this work, I proved that trichinous flesh is by no means 
 thoroughly disinfected by the usual treatment, and as little by salting 
 as by smoking. This statement, which therefore applies to salt pork, 
 smoked sausage, and ham alike, has been corroborated both by obser- 
 vation and experiment, 5 and thoroughly overthrows any faith in the 
 
 1 See a case cited by Rosenstein ("Kinderkrankheiten,'' 3d ed., p. 445, 1774) of such 
 a worm found living in a cooked bream. 
 
 2 Such a case was related to me by my since deceased friend Dr. Kriiger, in Brunswick. 
 A tolerably large cod-fish, which was cooked and brought to table, contained in its flesh 
 many dozen living Filarice. 
 
 3 Neue nord. Beitrdge, Bd. i., p. 98, 1781. 
 
 4 " Abhandl. von der Erzeugung der Eingew. Warmer," p. 3 : Berlin, 1782. 
 
 6 Compare Klichenmeister, Haubner, and Leisering, Bericht uber das Veterindr- 
 wesen Sachsens, p. 188, 1862; Rupprecht, "Die Trichinenkrankheit," p. 112, 1864; 
 Furstenberg, Wochenblatt der Annalen der Landwirthschaft, No. 30, p. 274, 1864; 
 Kiihn, Mittheilungen des landw. Institutes, p. 1-84, Halle, 1865 ; Perroncito, " Sulla 
 tenacita di vita del Cisticerco," Annali Accad. Agricdtur di Torino, vol. xix., 1876, and 
 vol. xx., 1877. 
 
158 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 harrnlessness of the flesh we use as food. One must not of course 
 think that heat and smoke (pyroligneous acid) and salt are without 
 any effect on the parasites lurking in the flesh. On the contrary, 
 one is at once convinced that these various influences are wholly, 
 though to different degrees, hurtful to the worms; but this also is 
 certain, that the action must attain a certain intensity and last a 
 certain time before the worms die. Trichina does not perish till 
 acted on by a temperature of from 62 to 69 C., but the temperature 
 which usually prevails in the interior of the flesh during boiling or 
 roasting is often somewhat below this, and in the case of large masses 
 or rapid cooking, is so very far from it that the interior remains 
 bloody. In such cases neither the developmental power nor the life 
 of the inmate could be very seriously affected. Much the same may 
 be said of other (cold) methods of smoking ; we know of many and 
 serious illnesses which have resulted from the parasites derived from 
 ham or brain-sausage. The danger of partaking of such kinds of 
 food is greater, since Trichina sometimes remains living for months 
 in masses of flesh so preserved. 
 
 I may further take this opportunity of noting that Trichina 
 has a special and uncommon power of resisting external influences. 
 It can not only remain living for weeks in the summer time in 
 putrefying muscle, but is, to a most remarkable extent, insensitive to 
 cold or frost. During the coldest part of January (at about 20 to 
 25 C.) 1 left a portion of trichinous flesh for three days and three 
 nights in the open air, and after thawing it in cold water, gave it 
 to a rabbit. I hardly looked for any result, and was most astonished, 
 after an interval of three weeks, to find the animal emaciated and 
 paralysed. Death ensued eight days later, and I then convinced my- 
 self that it was throughout infested with Trichinae. 
 
 Such considerations make it probable that the facts established in 
 the case of Trichinae cannot be directly applied to other worms. In- 
 deed, Cysticerci are killed by a temperature of 50 C., 1 and therefore 
 much sooner than the Trichinae. Their possible length of life in pre- 
 served foods is also shorter, rarely exceeding four or five weeks. But 
 there is here also sufficient possibility of infection, which is indeed 
 easy enough in the case of Tcenia saginata, since beef is often eaten 
 in a half-raw state, even after cooking. 
 
 To allay the apprehensions of our reader, we must not forget to men- 
 tion that infection through the medium of boiled or roasted flesh is on 
 the whole rare,since in the great majority of cases the parasites are killed 
 by the ordinary culinary treatment. This is as true of Trichina as of 
 
 1 This is the result of Perroncito's experiments, which agree with some which I have 
 lately made. Lewis fixed the necessary temperature at 62 '5 C., Pellizari even at 67 '5 C. 
 
DOMESTIC ANIMALS AS SOURCES OF PARASITES. 159 
 
 bladder- worms, as statistical results clearly prove. Thus, according to 
 official reports, there are above 30,000 swine eaten yearly in Leipsic, 
 out of which, according to the results of the Brunswick investigations 
 (which furnish as yet the most favourable fraction one trichinous 
 pig in 5000), there ought to be at least six infested with Trichina. 
 If the parasites were not rendered harmless by cooking, we ought 
 obviously to expect six epidemics of Trichina yearly, while in reality, 
 apart from a few isolated cases, there have been only two observed 
 since 1860 a severe one in the winter of 1877, and another less 
 serious. In Sweden, where in many districts 1 per cent, of the swine 
 are trichinous, the disease is only known as a sporadic malady, and 
 as such only rarely. 1 
 
 We have spoken mainly of the pig and the ox, since these animals 
 furnish the largest proportion of the food used by civilised peoples, 
 and, so far as we know, are the most common sources of parasites. 
 But we are also aware that other kinds of flesh may also infect us 
 with parasites. Thus the goat harbours the cystic stage of Tcenia 
 saginata, though not so frequently as the ox; the sheep and deer 
 sometimes contain the bladder- worms of Tcenia solium. Further, we 
 may find Trichina in the flesh of martens, foxes, rats, and hamsters 
 which are here and there used as food. The assertion of Herbst, that 
 pigeons and other birds were also infested with encapsuled Trichina, 
 is based on an error, for we are not yet acquainted with any bird 
 capable of infecting man with worms. It is otherwise with fishes, for 
 we have obtained convincing proofs through the observations and ex- 
 periments of Braun, 2 in Dorpat, that the pike (although it remains 
 questionable whether this is the only fish that does so) yields young 
 stages of Bothriocephalus latus to human beings. It is to be assumed 
 that Bothriocephalus cordatus of Greenland is also derived from the 
 flesh of some marine fish which harbours its young stage. It is found 
 not only in man but in dogs, which are fed by the Esquimaux, for the 
 most part, on raw or dried fish. At any rate, it must be some in- 
 habitant of the water which harbours the young stage of the human 
 Bothriocephalus, as we infer with every certainty from the cili- 
 ated coating, by means of which the embryos are able to swim 
 about. 3 
 
 The introduction of the germs of Helminths can also easily take 
 place through small terrestrial or aquatic invertebrates. Chance 
 
 1 See Vol. II. 
 
 2 Braun, " Zur Entwicklungsgeschichte des breiten Bandwurmes : *' Wiir/burg, 1883. 
 8 The assertion of Knoch ( Virchow's Arckivf. pathol. Anat, Bd. xxiv., p. 243 et seq., 1862) 
 
 that Bothriocephalus is developed without an intermediate host, was suspicious in the highest 
 degree, even before Braun adduced arguments against it. (See under " Bothriocephalidae," 
 
100 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 must, of course, determine many of the methods of infection. We 
 should as little think of eating a living snail as a bladder-worm. But 
 such an animal is easily hidden among salad and vegetables, which 
 we eat raw ; and this is specially likely when they have grown in 
 damp places, as is the case with water-cresses. Similarly, when eating 
 roots, fallen fruit, &c., we may easily swallow worms, insects, and other 
 small animals, without noticing it, and be infected with parasitic 
 germs of various kinds ; and where such creatures are eaten as food or 
 as tit-bits, as happens especially among savage peoples, other methods 
 of infection are obviously open. 
 
 We know, of course, as yet but few instances which prove a 
 transmission accomplished in this way. Infection with Tcenia cucu- 
 merina must be referred to this class. This parasite occurs not un- 
 frequently in children, and is transmitted through the dog-louse 
 (Trichodectes), in which the worm passes its immature stages ; 1 but 
 this mode of transmission is probably rare and local. 
 
 Under some circumstances, drinking water is the medium of in- 
 fection. This is especially the case when the water is derived from 
 ponds or reservoirs inhabited by numerous small organisms, or abound- 
 ing in organic remains. Small Crustacea (Cyclops) swallowed along 
 with the water transmit the Guinea-worm, which, according to Fed- 
 schenko, 2 passes its early life in these animals. And besides trans- 
 mitters of parasites, we find here and there in such water free-living 
 immature stages of such worms as Dochmius trigonocephalus, which 
 are carried with the water into the intestine, and there settle down. 3 
 
 The older physicians were wont to emphasise the use of fruit and raw 
 vegetables as the means of introducing certain forms of worms, and this 
 is, in a certain sense, as we now know, perfectly justifiable ; but only 
 in a certain sense, for we know with absolute certainty of no instance, 
 either among men or animals, where vegetable food furnishes in itself 
 either a transmitter of parasites or a parasitic germ ; yet the possi- 
 
 postea. ) The same may be said of the old conjecture, that the common custom of watering 
 celery beds, &c. with the liquid contents of dung-heaps resulted in the importation of the 
 eggs of BothriocepJicdus, which at once developed into tape-worms in the intestine, especi- 
 ally as the eggs of Helminths found in dung-heaps can hardly ever be in a condition capable 
 of germination. Otherwise, it might be supposed that infection with bladder-worms (not, 
 as is sometimes said, with tape-worms) was sometimes brought about in this way by the 
 eggs of Tcenia solium. 
 
 1 See VoL I., also Melnikoff, Archivf. Naturgesck., Jahrg. xxxv., Bd. L, p. 62, 1869. 
 
 a See Vol. II. 
 
 3 See Vol. II. I may add that Perona and Grassi (" Sullo sviluppo dell' Anchylo- 
 stoma duodenale," Pavia, 1878) have meanwhile proved, by their researches into the 
 immature state of Dochmius duodenalis what VVucherer also (Gazeta medico, di Bahia, No. 
 65, 1869) had previously shown, viz., that the life-history of Dochmius triyonocephalus was 
 similar to that of this worm. 
 
INFECTION BY MEANS OF WATER. 161 
 
 bility of such being the case must in nowise be overlooked. 1 We 
 are, of course, dealing only with the ordinary course of events, for 
 vegetables are as liable as flesh to an accidental association with 
 either adult or embryonic parasites. We have, indeed, every reason 
 to suppose that along with raw vegetable food certain thread-worms 
 (especially Tricliocephalus and Oxyuris) very commonly find their way 
 into man in the form of eggs, containing embryos. 
 
 It seems very doubtful whether there be any internal worms 
 which bore their way into man, like the itch-mite or female chigoe. 
 The only example which could be cited of such a mode of infection 
 was the Guinea-worm, and in regard to this form also the theory has 
 been disproved by the above-mentioned observations of Fedschenko. 
 
 The itch-mites and chigoes behave like those parasitic insect- 
 larvae which occur in superficial organs, like the larvae of (Estrus in 
 the sub-epidermal connective tissue, or the larvae of Musca, found in 
 the ear passages, or in the nasal cavity, &c. The latter differ, indeed, 
 in this that it is the free-living mother which places them in these 
 various situations. 2 When the grubs are found living in the intestine, 
 the introduction of eggs or larvae has taken place mostly by means 
 of cold meat, cheese, &c., just as we saw to be the case with the in- 
 testinal worms ; or in some instances the eggs may have come directly 
 from the mother, having been laid on the lips or tongue during sleep. 
 
 Cases of parasites actively forcing an entrance into man are then 
 rare and restricted to a few forms. The true parasites the parasites 
 fear ifyyfiv exhibit no instance of it, and thus we may conclude 
 that the accidental introduction of eggs and immature stages is, after 
 all, ly far the most frequent and most constant source of the human 
 Entozoa. 
 
 Every one exposed to one or other of these modes of introduction, 
 runs the risk of being infected with worms of various kinds, accord- 
 ing to circumstances. 
 
 OCCURRENCE AND DISTRIBUTION. 
 
 One often hears of a certain liability to helminthiasis varying 
 with age, sex, and even nationality. 
 
 1 The statement of Ercolani, that the Anguillula and Rhabditis of plants become 
 genuine parasites after their transference into the intestine of animals, rests upon a 
 delusion. [On the other hand, the fact that the introduction of Distomum hepaticum is 
 effected from water-plants or marsh -plants, on which its Cercarise are encapsuled, has 
 been made extremely probable through the investigations of Thomas and myself. R. L.] 
 
 2 As a rule, these insects are only induced to lay their eggs by some evil-smelling 
 excretion. On this point see v. Frantzius, Virchow's Archiv f. pathoL Anat., Bd. xliii., 
 p. 98, 1868. 
 
 L 
 
162 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 I have, indeed, expressly stated (p. 85) that certain individual 
 characteristics, such as age, exercise a distinct influence on the de- 
 velopment of the imported germ ; but at the same time I believe that 
 the majority of cases cited in support of the theory of a definite 
 liability, will admit of another interpretation. When, for example, 
 we find that children are more frequently infested by thread-worms, 
 or by Tcenia cucumerina, than adults, and that they are but rarely 
 subject to the common tape-worm, that does not denote, in my 
 opinion, that children 1 have a greater disposition to the first-men- 
 tioned worms, but only that they have, in the natural conditions of 
 their life, much more opportunity to infect themselves with the larval 
 stages of these parasites. I need only urge in support of my con- 
 tention that children eat or suck all sorts of things without choice or 
 distinction, and have therefore abundant opportunity to infect them- 
 selves with various transmitters of parasites, with which they would 
 not, under ordinary circumstances, come into contact. 
 
 In the same way we may explain the very abundant occurrence of 
 parasites which Vix has lately shown to be attendant on those mental 
 diseases which are characterised by voracity. The "dirt-eating," 
 which Vix would regard as a consequence of the helininthiasis, seems 
 more probably the cause of it. 
 
 Nor is it, of course, a sign of a special " predisposition " that the 
 female sex suffers more frequently (in the proportion of two to one 
 according to Wawruch) from Tcenia saginata and T. solium, since the 
 household duties of women expose them to a much greater danger of 
 infection by cystic worms. If not, we must consistently credit cooks 
 and butchers with a similar disposition to tape-worm, and even to 
 sporadic trichinosis, since they are of all persons most troubled by 
 these parasites. 2 It is the trade which explains the frequency, just 
 
 1 According to Gribbohm (loc cit., p. 7), the per-centage of children below ten suffering 
 from Ascaris is 24*6, as compared with an average of 18*3. Similarly, as regards Ojri/uri*, 
 the per-centage is 31 "6, as opposed to the average 23 '3 ; and in the case of Trichorcpkalus, 
 33 '3, as compared with 32*2. The total number of children below twenty infested with 
 intestinal Nematodes is not less than 62 per cent, while the average for all ages is 
 only 43 '5. The number of the cases used as a basis of calculation (Gribbohm bases his 
 conclusions on 1117 post mortem examinations) is, of course, much too small to give certain 
 results. In this way, we can understand how Muller, depending on the statistical results 
 of the Dresden and Erlangen Hospital (" Zur Statistik der menschlichen Entozoen," 
 Erlangen Dissert., 1874), contradicts the commonly received opinion, by stating that 
 Ascaris and Oxyurls are not, on the whole, more frequent among children than among 
 older persons. We may further note that Tcenia cucumerina has only been observed in 
 children and never in adults. 
 
 8 This observation dates from the beginning of this century, and seems to have been 
 first made by Fontassin. Wawruch, to whom we owe the most extensive information as 
 to the statistics of the tape-worm, found that of 206 patients more than a quarter belonged 
 to the above occupations. 
 
INFLUENCE OF SEX AND OCCUPATION. 163 
 
 as it is abstinence and not nationality which protects the Europeans 
 in Abyssinia from tape-worm (p. 156). 
 
 In judging such cases, we must, above all, remember that the fre- 
 quency of the occurrence of intestinal worms is determined primarily by 
 the opportunities for the transmission of the emtoyos or larval forms. 
 Customs, habits, occupation, and mode of life deserve the first con- 
 sideration, and have a much greater influence on the occurrence and 
 distribution of parasites than age, sex, or nationality can ever have. 
 After what we have said, it may indeed appear as if the etiological 
 import of the latter factors were after all only apparent, or at least 
 dependent on the numerous inter-relations between them and the 
 true causes. 
 
 What we have emphasised above explains why the appearance of 
 certain forms of helminthiasis is often in striking dependence on condi- 
 tions of time and space. 
 
 In the first connection we have as yet but little material as far as 
 man is concerned, and what we have is uncertain, in so far as many 
 parasites have a somewhat long life, and do not at once attract 
 attention. We may, however, advance thus much, the thread-worm 
 is said to be most common in autumn, 1 as we might indeed expect 
 from its rapid growth already mentioned, whilst Tcenia solium, on 
 the other hand, according to the results of professional helmin- 
 thologists, calls for treatment more frequently in summer, which leads 
 us to regard the infection as having taken place in winter, since the 
 tape-worm requires several months before it makes itself noticeable 
 by the expulsion of proglottides. Indeed, one can hardly doubt that 
 it is in the winter months that the increased consumption of flesh, 
 and the custom of killing animals used for food at home, afford 
 specially favourable opportunities for infection with bladder-worms. 
 For similar reasons Trichina, with only a brief period of incubation, 
 is far more frequently observed in winter than in summer. 
 
 The evidence furnished by the worm diseases of our domestic 
 animals is still more convincing. These occur in most obvious de- 
 pendence on certain periodically recurrent causes. The sheep-cough 
 (Strongylusfilaria), which attacks our flocks in late autumn, may with 
 certainty be said to arise from the meadow pastures, just like the 
 Coenurus, which appears mostly at Christmas, or like Echinorhynchus 
 yigas, which only appears in those swine which have been fed in the 
 open air. Even our geese are infested with worms (especially with 
 Tcenia lanceolata) only while they are seeking their food through 
 
 1 According to Gribbolim, the maxiimun of cases of Ascaris occurs in February (loc. 
 cit., p. 9). In the same way, Oxyuris is most prevalent in January, and Trichocephalui 
 in April. There are fewest cases in August, October, and November. 
 
164 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 field and pasture, and afterwards lose them during the subsequent 
 fattening. x 
 
 It is also a well-known fact that liver-rot (Distomum hepaticum) 
 and verminous inflammation of the lungs (Strongylus) are much com- 
 moner among our horned cattle in some years than others. We even 
 know of epidemics of this kind which have in many districts almost 
 destroyed the cattle for a long time. Wet seasons especially have 
 this pernicious result, since long-continued rainy weather assists the 
 transportation of the young brood or of the intermediate host, and 
 greatly increases the possibility of infection. 
 
 Even among human parasites there is one, on the occurrence 
 of which a damp season has an undeniable influence. This is the 
 Filaria Medinensis of the tropics, the periodically varying degree 
 of whose occurrence has long excited the attention of observers. The 
 register of the native general hospital in Bombay shows, according to 
 Carter, 2 that during the years 1851 and 1858 the maximum of sixty- 
 three cases occurred in August, the minimum of twelve in February, 
 and forty-four in the month of May. The results of observations in a 
 military hospital ought to be still more reliable, since the soldiers 
 would at once seek relief on the discovery of the trouble. And these 
 results are so far different, that e.g., in Sattara, a garrison town 100 
 miles from Bombay three-fourths of all the cases were treated be- 
 tween March and June. According to the observations of seven years, 
 the maximum occurs in May (125 cases) and in June (102), and the 
 minimum in January (11). We may therefore conclude that it is in 
 the two months at the end of the dry season and beginning of the 
 wet that the disease most frequently manifests itself. From many 
 cases of infected sailors who have spent only a short time in a place 
 it has been determined that the Guinea-worm requires ten or twelve 
 months for its perfect development, and we can therefore further con- 
 clude that it is during the rainy season that this parasite finds 
 entrance. 3 
 
 The local and endemic occurrence of parasites must be discussed 
 from the same point of view. We should expect, a priori, that the 
 frequency of helminthiasis would be in inverse ratio to culture and 
 civilisation. Filthy and careless habits, the frequent eating of raw 
 
 1 Bloch has already recognised this fact (" Abhandl. liber die Erzeugung der Eingew. 
 Wurmer," p. 10, 1782), and has correctly found its reason in the altered nourishment. In 
 other cases the parasites acquired in youth, during a particular time, continue on into 
 later life. Thus, for instance, the Pdystomum of the bladder and the Opalinw of the 
 rectum in frogs, both date from the time of the larval condition. See Zeller, Zeitschr. f. 
 wits. Zool., Bd. xxvii., p. 238, 1876, and BcL xxix., p. 352, 1877. 
 
 3 Ann. and Mag. Nat. Hist., ser. 3, vol. iv., p. 110, 1859. 
 
 8 For further details see Vol. II. 
 
INFLUENCE OF TIME AND LOCALITY. 165 
 
 food, and especially of raw flesh, insects, and snails, the close associa- 
 tion of man and beast, and, in short, all the external characteristics of 
 savage life, are, as we have seen, most important causes of parasitic 
 diseases, and facts, so far as we know them, bear this out. Nowhere 
 are intestinal worms more frequent than among savage peoples, especi- 
 ally in the tropics, as has been long ago sufficiently established, and 
 lately confirmed by travellers and physicians, especially in the case of 
 Africa. In Abyssinia, for example, every inhabitant, male or female, 
 is infested with intestinal worms from his fourth or fifth year. Similar 
 results might be given in regard to the American slaves, the Esqui- 
 maux, and the Buratis, among the lower class population of the East 
 Indies. Of course the same parasites do not prevail throughout. The 
 negroes of the West Indies are specially plagued with Ascaris; the 
 Abyssinians most commonly harbour Tcenia, due, as has been sup- 
 posed since the time of Bruce, to their general use of raw meat. Since 
 the flesh of swine is avoided by the Abyssinians, it is of course not 
 Tcenia solium, but Tcenia saginata, which occurs. The latter is associ- 
 ated with the ox almost throughout the world, while the former, like 
 Trichina, is specially prevalent in those lands where swine are generally 
 bred. 1 A difference may even be observed in neighbouring districts 
 like North and South Germany. In Berlin Tcenia solium, and accord- 
 ingly its related Cysticercus cellulosce, are not at all rare in man, but 
 both so uncommon in Vienna that physicians sought long in vain for 
 the latter, and not being in a position to distinguish Tcenia saginata 
 from Tcenia solium, regarded the reports of the Berlin physicians as 
 to the frequent occurrence of bladder-worms in the eye with uncon- 
 cealed distrust. We can similarly understand how the famous hel- 
 minthologist Bremser, living in Vienna, was never convinced of the 
 existence of a circle of booklets in the human tape-worm till Eudolphi 
 sent him the head of a Tcenia solium from Berlin. Where the use of 
 flesh decreases, the supply of certain Helminths becomes less copious, 
 the worms themselves being less numerous ; but the difference may 
 
 1 In Denmark Krabbe found Tcenia solium only 53 times in 100 cases of tape-worms, 
 T. saginata 37 times, T, cucumerina once, and Bothriocephalus 9 times. The proportions 
 were similar in Giessen, where out of 57 tape-worm patients only 12 were infected with 
 Tcenia saginata. On the other hand, among 35 tape-worms observed in Florence by 
 Marchi, there was only a single Tcenia solium. But these proportions vary according to 
 circumstances. Thus Krabbe writes to me that since 1869, up to which time the above 
 numbers held true, T. saginata has become relatively more frequent in Copenhagen and 
 its surroundings. Out of 78 new cases since that time, there were only 16 of Tcenia 
 solium, but not less than 46 of T. saginata, 4 of T. cucumerina, 10 of Bothriocephalus. 
 Krabbe looked for the cause of this partly in the Trichina-panic, which had considerably 
 restricted the use of raw swine's flesh, partly in the greatly increased use of raw beef in 
 illnesses. And in Northern Germany, according to my personal experience, the occurrence 
 of Tcenia solium has in a decennium become much less frequent. 
 
166 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 be annulled by greater negligence in the preparation of the food. This 
 is especially true of trichinosis, which is hardly less frequent in the 
 villages and among the lower classes than it is in towns and among 
 the well-to-do, although the number of tape-worms, especially when 
 compared with that of thread-worms, is considerably less in the former 
 than in the latter. 
 
 It is impossible, without special knowledge of the various life- 
 histories, to bring the local conditions of parasites into relation with 
 the customs and manner of life of the inhabitants. We must, there- 
 fore, leave many of these problems as yet undetermined, e.g., where 
 the 63 per cent, (according to Bilharz and Meckel) of Fellahs and 
 Copts derive the Distomum hcematdbium from which they suffer, or 
 why Filaria sanyuinis is so frequent in tropical countries. 
 
 On the other hand, we can at once understand the similar distri- 
 bution of Dochmius duodenalis when we remember that this worm 
 passes its youth freely in water, and that stagnant or slowly flowing 
 water is oftener used for drinking in tropical than in colder zones. 
 Similarly we are probably justified in referring the frequency of 
 Uchinococcus among the Icelanders, and other pastoral peoples, to their 
 close and constant contact with numerous dogs, 1 and to the generally 
 associated want of cleanliness. This disease seems to have been in 
 former centuries much more frequent in Germany than it is now, 
 when custom demands that dogs be kept at a greater distance, and 
 when the dog-tax has also very considerably lessened the number of 
 those animals. 2 
 
 We have spoken as yet only of the local occurrence of helmin- 
 thiasis, without special regard to its geographical distribution. The 
 latter is, in many respects, independent of custom and mode of life. 
 It is determined, on the whole, less by man than by the distribution 
 of the intermediate hosts, and by the temperature of the region. 
 
 The importance of warmth as a factor in the distribution of worms 
 may be inferred from what we have already seen (p. 73), that a 
 certain temperature is requisite for the development of the embryo. 
 When this temperature is not attained, or does not last long enough 
 to be efficient, the worm cannot continue to exist. Thus, Ascaris lum~ 
 bricoides is wanting in those tracts where the temperature does not 
 
 1 On this point consult Krabbe ("Recherches helminthol.," p. 60), who also mentions 
 that in Iceland there is one dog for every eleven inhabitants, while in Germany there is 
 only one for every fifty, and that besides Tcenia echinococcus is much commoner in Icelandic 
 than in German dogs (see p. 152, note). 
 
 * When (1883) the dog-tax in the Grand Duchy of Baden was lowered from 3 florins to 
 1-1^ fl. yearly, the number of dogs increased to one for every twenty-eight inhabitants, 
 while before, with at a tax of 3 fl., and now with a 4 fl., there was only one to every forty- 
 nine. 
 
INFLUENCE OF CLIMATE. 167 
 
 rise above 20 C., or only attains it for a short time. It is all but 
 unknown in Iceland (according to Krabbe), although distributed 
 throughout the Temperate and Torrid Zones. Trichocephalus has a more 
 restricted distribution, since its eggs require still greater warmth. If 
 the temperature required for hatching were in itself decisive, Oxyuris 
 (with a requisite temperature of 38 C.) ought hardly to be found outside 
 the tropical countries, while in fact it is extraordinarily abundant in 
 the far north, and more widely distributed there than elsewhere 
 (Ohlrick). This cosmopolitan distribution is explained when we 
 consider that the aboye-mentioned high temperature is only needed 
 for a few hours to develop the embryos. The warm skin of man 
 affords the requisite conditions of development equally well among 
 the Esquimaux as among the natives of tropical climes. The Oxyuris 
 patient thus bears the means of infection on his own person trans- 
 mission to the mouth is a simple matter the easier, the less the 
 attention paid to the cleanliness of the body and clothing. 1 
 
 We hardly need to discuss how the distribution of Helminths is 
 affected by the habits of the intermediate hosts. Where they are 
 absent there can obviously be no parasite. 2 Parasite and intermediate 
 host are in their occurrence as closely bound up with one another, as 
 Herbivora and the plants upon which they feed. 
 
 We cannot doubt that in the course of time, when our knowledge 
 of the life-history of human intestinal worms is more complete, we 
 shall be able by the discovery of the intermediate hosts to explain the 
 causes of the more or less restricted distribution of some of these 
 parasites. It is especially in regard to the as yet but little known 
 tropical Entozoa that we look for further progress in this direc- 
 tion. The only tropical worm whose intermediate host we know 
 is Filaria Medinensis, which passes its larval life in animals 
 (Cyclops) which are among the most frequent inhabitants of our 
 fresh water. This seems hardly to justify the hope expressed above, 
 but we must remember that, besides the factors emphasised above, 
 many chances of the most diverse kind influence the occurrence of 
 parasites. 
 
 It not unfrequently happens that even when the conditions 
 of occurrence are present, the species occur in one place abun- 
 dantly, but are entirely absent even in the near neighbour- 
 
 1 It is therefore not so surprising that Oxyuris occasionally occurs in sucklings. Grib- 
 bohm saw them in infants five weeks old, but Ascaris and Trichocephalus only in the 
 eleventh month (loc. cit. t p. 6). In contradiction to this statement, however, we read in 
 Goze : " We find instances of large thread -worms voided by infants hardly a month old, 
 who have tasted only their mother's or nurse's milk " (loc. clt., p. 66). 
 
 2 Thus, e.g., Taznia serrata, so common in Germany, is not found in Iceland, where 
 there are no hares or rabbits (Krabbe). 
 
168 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 hood. 1 Just as for free-living animals, so for parasites, there are 
 within the area of distribution certain more or less restricted haunts, 
 in which the creatures occur either exclusively or at least much 
 more frequently. Where any intestinal worm has once established 
 itself in virtue of a fortunate combination of favourable conditions, 
 there it remains for long, indeed till the conditions change, for the 
 possibilities of infection increase in proportion to the number of the 
 parasites. 2 In this way there arise what have been called " foci 
 of infection," especially in our time in the case of Trichina, but also 
 of tape-worms and other parasites. By such " foci," helminth iasis 
 may be spread over an ever-increasing area. Thus Filaria Medinensis 
 has been carried by slaves from the west coast of Africa to Tropical 
 America, and has thus obtained a wide distribution. Since the 
 intermediate host of this parasite is one of our commonest animals, 
 the worm is therefore in no way restricted to Asia or warmer climates, 
 and its acclimatisation in our own country is by no means an im- 
 possibility. 
 
 When opportunities of infection multiply in any way, then there 
 arise, even among men, decided worm-epidemics. Knox tells of a 
 formidable tape- worm epidemic which broke out in October 1819 
 among the English soldiers engaged in the Kaffir war, after they had 
 been feeding for a lengthy period on the flesh of overdriven and un- 
 healthy oxen. 8 Similarly, in the year 1820, a fourth part of the 
 Egyptian army serving under Mohamed Bey in Kordofan suddenly 
 fell victims to Guinea- worms after they had remained healthy for two 
 years. 4 And according to Bartholin and Kiichenmeister the "fiery 
 serpents " of the Old Testament were most probably Guinea-worms. 
 
 The epidemics of Trichina which occur every year in North 
 Germany are so well known that it seems almost unnecessary to 
 devote special attention to them. An epidemic appearance of Ascaris 
 has also been described in former times. But what they then 
 called worm- epidemics were mostly dysenteric troubles, in the course 
 
 1 [For an instance of this in the case of Distomum, see Thomas, Quart. Journ. Micr. 
 Sci. y N. S., vol. xxiii, p. 99, 1883. W. E. H.] 
 
 2 In the Punjaub, where Tcenia saginata is in certain sections of the population 
 almost as frequent as in Abyssinia, in 1869, according to official reports, not fewer 
 than 5 '55 p.c. (in 1868 even 6 '12 p.c.) of the oxen slaughtered at the military stations 
 were infected, and badly so, with cystic worms. (See Lancet, p. 860, Dec. 1872.) The 
 natural occurrence of Cysticercus in cattle is exceedingly rare with us. Similarly T. 
 marginata, T. coenurus, and T, echinococcus in dogs, are in Iceland 4, 18, and 47 times 
 commoner than in Denmark (Krabbe), and the same proportion holds for the related cystic 
 stages. 
 
 3 Froriep's Notizen, Bd. i., p. 122, 1822. Friedberger observed a disease due to tape- 
 worms among pheasants, Zeitschr. f. Veterinarwiss., p. 97, 1877. 
 
 * Clot, " Aper?u sur le ver dragonneau," Marseilles, p. 30, 1830. 
 
RATIONAL PROPHYLAXIS. 169 
 
 of which thread-worms were often seen to be voided. It is, however, 
 doubtful whether these worms were directly concerned in the disease, 
 though it is in no way improbable that thread-worms should under 
 abnormal circumstances be introduced in extraordinary numbers. 1 
 
 The foregoing discussion has shown us the ways and means 
 by which man becomes infested with intestinal worms or with 
 their larvae. It may also serve to anticipate a rational prophy- 
 laxis, or to suggest the lines along which this must be sought. The 
 first law of this prophylaxis is simply, shield yourself from even/ cir- 
 cumstance ly which parasites could le introduced; but the difficulty 
 of following this out in detail is as great as the law is short ; we can- 
 not protect ourselves against unknown and unseen foes such as we 
 have here to deal with. Helminthiasis will never disappear ; never- 
 theless a rational prophylaxis can limit its propagation and restrict its 
 distribution, and in so doing confer a great benefit on health and life. 
 
 This prophylaxis depends above all things on cleanliness, especi- 
 ally in the kitchen and house. Eaw foods cannot be too carefully 
 inspected, whether they be of vegetable or animal nature. Flesh 
 must be kept away from the preparation of other food (bread) and from 
 the dishes and other vessels used. Cooking ought to be characterised 
 by due carefulness ; sausage and ham bought in small quantities from 
 the butcher ought to be subjected to close scrutiny. Still more should 
 flesh which is eaten raw be carefully examined. Water, and especially 
 drinking water, should be clear and pure. Dogs and other domestic 
 animals should be kept out of the kitchen and dining-room. Contact 
 with them should be as far as possible restricted, and should be at 
 once wholly suspended when they in any way show suspicious 
 symptoms of helminthiasis. The food of dogs and pigs should consist 
 preferably of cooked stuffs, and never (as in slaughter-houses and 
 skinning sheds) of the remains of slaughtered or of dead animals. 
 Rats, which infect the pigs with Trichina, ought to be kept away 
 from the styes. Excrement should be deposited in inaccessible places, 
 and any tape-worms present (especially Tcenia solium) removed as 
 speedily as possible. 
 
 Precautions such as these should be taken against the worms pre- 
 valent in Europe. Other rules apply to the Epizoa, and especially 
 concern contact with other men, e.g., in the use of beds, linen, and 
 clothes. 
 
 All this is in the first place applicable only to individuals and 
 families. When similar dangers threaten to affect the community, 
 
 1 Gbze mentions (" Versuch. einer Naturgesch., u. s. w.," p. 23, note 2) the case of a 
 family in Brunswick, in which all the members, from father to child, and even the two 
 maids (two workmen alone excepted), were infected with Ascaris. 
 
170 THE EFFECTS OF PARASITES ON THEIR HOSTS. 
 
 more thorough-going measures must be taken in regard to water- 
 supply, dung-hills, and drains, as well as in regard to slaughter-houses 
 and the treatment of the flesh. What has already been provided 
 for by sanitary regulations is by no means sufficient nor in keeping 
 with the progress of science. We shall refer only to the regulations 
 about measly flesh, which in many places allow it to be sold raw, if 
 the bladder-worms are " not numerous," though never in the form of 
 sausage or similar preparations, though it is just this last process which 
 renders the cystic worms somewhat harmless. The measures taken 
 against Trichina also admit of manifold improvement. It is above 
 all necessary to popularise the facts known about parasites and their 
 origin, and even to make this a subject of instruction in schools. 
 
SECTION II. 
 
 SYSTEMATIC ACCOUNT 
 
 OF THE 
 
 PAEASITES INFESTING MAN. 
 
INTRODUCTION. 
 
 THE number of parasites as yet observed in man, including some 
 doubtful species and merely temporary visitors, amounts to nearly 
 sixty. We know no other creature which harbours so large a 
 number, but it is open to question whether this may not be simply 
 due to the fact that special attention has been devoted to man and 
 human parasites. On the other hand, we can hardly suppose that 
 the whole list of human parasites is yet known to us. From the 
 results of the last few years, we are led to the conclusion that there is 
 still, especially beyond the bounds of Europe, a crowd of unknown 
 human parasites. Nor is our knowledge of European species yet ex- 
 haustive ; we know of many doubtful forms, and have been enabled 
 in our own day to render the catalogue more complete. 
 
 Of course the parasites infesting man have not by any means equal 
 importance from a medical point of view. Besides dangerous or even 
 fatal forms, we find others which usually exert hardly any influence 
 whatever on the health of their host. The study of their distribution 
 reveals also similar differences. Some though on the whole only a 
 few are exclusively restricted to man ; J others infest other animals 
 also, and many of these occur indeed more frequently in other than 
 human hosts, which they may perhaps have visited only once by 
 chance ; and further, we know that some of our parasitic visitors 
 (larvae of insects) generally prefer free life to parasitism. 
 
 Most parasites infest the human body only in their adult and 
 sexually mature state ; but to this statement also there are exceptions. 
 Some species, such as Tcenia solium and Trichina spiralis, are found 
 in man in two stages, while others are only parasitic in their larval 
 or intermediate form, e.g., Tcenia echinococcus, as a cystic worm. 
 
 As regards the special parts of the organism which are infested, 
 we find that in man the skin and the intestine are, as usual, most 
 exposed to the assaults of parasites. By far the greater number of 
 parasitic species concentrate themselves in these two organs, and 
 only a fourth of the whole number are found throughout the rest of 
 the body. Yet there is hardly any part of the body which is without 
 
 1 With the increasing completeness of our knowledge of helrninthology, the number of 
 these parasites is becoming ever smaller. Thus I have lately found in the gorilla, not 
 only Ascaris lumbricoides, but also Dochmius duodcnalis, which had previously only been 
 found in man. 
 
174 INTRODUCTION. 
 
 its parasitic guest, which may be either a definite and peculiar form, 
 or one which occasionally visits other organs, and which may perhaps 
 only occasionally wander from them. Of this we shall, in the course 
 of our systematic study, find abundant illustration, and it is at this 
 stage only necessary to observe that the distribution of parasites 
 within the human body is very diverse and unequal. While some 
 species are confined to definite, and perhaps strictly limited areas, 
 others wander to the most various organs, and some (e.g., Echinococcus) 
 hardly seem to avoid any part of the body. 
 
 As regards their systematic position, the parasites of man belong 
 to three different divisions of the animal kingdom the Protozoa, the 
 Vermes, and the Arthropoda. The Vermes furnish the largest con- 
 tingent, the Protozoa the smallest but both only internal parasites 
 while the parasitic Arthropoda are almost wholly external. 
 
SUB-KINGDOM I. PROTOZOA. 
 
 THE organisms which, following von Siebold, we here include under 
 the name " Protozoa," form a division of the animal kingdom whose 
 members, in part at least, can only be distinguished with difficulty, 
 if indeed at all, from the lowest plants. x 
 
 The most essential characteristic of these Protozoa lies in their 
 minuteness and in the simplicity of their structure, two characters 
 which to a certain extent involve each other. For the most part 
 invisible to the naked eye, and but rarely attaining the diameter of a 
 millimetre or more, they possess a body devoid of anything deserving 
 the name of organs, and often discharge their vital functions as simple 
 minute masses of animal substance, without any differentiation what- 
 ever. 
 
 As early as 1845 von Siebold endeavoured to compare the structure 
 of the Protozoa with that of the ordinary cell, or, in other words, to 
 define the Protozoa as unicellular animals ; 2 and this assumption has 
 been fully justified in regard to the vast majority of these organisms. 
 It is, however, true that we have in the course of time discovered some 
 Protozoa in which as yet a nucleus has been sought for in vain (the so- 
 called "Monera"), and others which might perhaps be more correctly 
 termed cell-aggregates, as evidenced by the possession of numerous 
 nuclei, were it not that in all these cases the component cells are so 
 
 1 It is not my intention to enter further into the relations between plants and animals. 
 This much, however, must be noted, that in the simplest animal and vegetable organisms we 
 find neither in structure nor in function any of those fundamental differences which usually 
 separate the higher representatives of the two kingdoms. From this it does not, how- 
 ever, in any way follow that we are bound to separate off these simple organisms from the 
 others, and make a special intermediate kingdom of them, as Hogg and Haeckel have 
 lately done (Protoctista, Hogg Protista, Haeckel). By the creation of this heterogeneous 
 intermediate kingdom, which includes forms so widely separated as the Infusoria and 
 Fungi, the difficulty of determining the boundaries is not diminished, but doubled ; instead 
 of there being only one uncertain boundary line, there are two. [With respect to this 
 point, it may be urged that a scientific classification is not merely an arrangement for 
 practical convenience, but rather a method of expressing our views as to the relations of 
 organisms. If, in conformity with the evolution theory, we hold that plants and animals 
 sprang from a common stem, then " Protista " must have once existed, and if so, they 
 ought to find a place in our scheme. The question whether it is easier to draw one 
 boundary line or two seems quite beside the mark. \V. E. H.] 
 
 2 " Lehrbuch d. vergl. Anat. d. wirbellosen Thiere:" Leipzig, 1845; and Zeitschr. f. 
 wiss. Zool, Bd. i., p. 270. 
 
176 PROTOZOA. 
 
 slightly separated that the structure of the whole organism is hardly 
 perceptibly modified. While in other animals tissues arise fitted 
 according to their properties for the discharge of various functions, the 
 Protozoa possess only a body-substance more or less homogeneous in 
 nature and similar in functional capacity. 
 
 Since we have learnt to recognise in the cells of an organism not 
 only the ultimate anatomical elements, but also the physiological units 
 of all vital processes, and are, in other words, convinced that the 
 single cell lives and represents an organism (elementary organism, 
 according to Brlicke), it cannot any longer seem strange that there are 
 plants and animals which consist only of a single cell, or at least of 
 something equivalent, and which nevertheless perform essentially the 
 same vital processes as higher organisms, built up, perhaps, of millions 
 of cells. 
 
 An animal of this kind possesses neither muscles nor nerves, and 
 has yet the capacity of motion and of sensation; it receives and 
 digests food without an alimentary canal, secretes without glands, and 
 reproduces its kind without sexual organs. All the functions which 
 in the higher organisms are severally discharged by diverse and de- 
 finite groups of cells and cell-derivatives, are here perfectly discharged 
 by a single cell, which constitutes the body of the animal. 
 
 This body is not, however, always of perfectly homogeneous char- 
 acter; for in spite of their general simplicity, the Protozoa often 
 exhibit a certain histological and physiological differentiation similar 
 to that which we observe in the individual cells of higher organisms. 
 
 Not only is the outer surface of the living protoplasm often hardened 
 to form a cuticle, which permits of ingestion and excretion only endos- 
 matically, but the protoplasm itself exhibits a differentiation into a 
 firmer outer portion, more or less exclusively the seat of motion (and 
 sensation), and a more fluid inner portion, which discharges the func- 
 tions of digestion and absorption. Like the protoplasmic contents of 
 the muscle cells, the contractile outer sheath can even acquire a 
 fibrillar consistency, by which it becomes fitted for even more energetic 
 discharge of its functions ; and through the contractility of the outer 
 portion, vacuoles, which originate there, become established as pulsat- 
 ing vesicles. Here and there, too, in the body-substance, holes and 
 openings appear, which, breaking through the cuticle and ectosarc, 
 represent the mouth and anus, much in the same way as similar 
 arrangements occur in the cells of higher animals (e.g., the so-called 
 " goblet-cells") for like purposes. In many cases (among the Infusoria) 
 further differences may be based even on the varied form and fate of 
 the nucleus. 
 
 Thus we see that even among the Protozoa numerous and striking 
 
UNICELLULAR ORGANISMS. 177 
 
 modifications of structure are beginning to appear. In many cases this 
 differentiation induces a sort of superficial resemblance to more highly 
 specialised organisms, such as worms and other multicellular creatures, 
 which, in opposition to the Protozoa, have been lately called "Metazoa." 
 "We can thus understand how it was that a famous investigator once 
 attempted to interpret the organization of the Infusoria (which are, 
 however, conspicuously Protozoa) entirely in accordance with the 
 analogy of higher, and indeed of the highest animals. 1 
 
 This attempt, indeed, was made at a time when there was not only 
 no knowledge of the structure of the single cell, nor true insight into 
 the histology of the animal body, but when the Infusoria were almost 
 the only Protozoa known. Through the discovery and study of other 
 forms (especially through the labours of Stein, Johannes Mliller, Lieber- 
 klihn, Haeckel, and Hertwig), a belief in a "perfect organization" of 
 the Protozoa has become impossible, for the vast majority of them are 
 destitute of that differentiation which distinguishes the Infusoria, 
 and exhibit characters which stamp them indisputably as unicellular 
 
 anisms. 
 
 If we are rightly to express the morphological nature of the Pro- 
 tozoa, we cannot of course support the old idea of Schwann, according 
 to which the cell was " a hollow nucleated vesicle, surrounded by a 
 transparent structureless wall," in which the contents are of only 
 subordinate importance. While it is true that the cell membrane is, 
 in virtue of its properties of firmness, porosity, &c., of most funda- 
 mental physiological importance in the economy of the cell, yet, on 
 the other hand, it is equally certain thanks especially to the investi- 
 gations and generalisations of Max Schultze that it is by no means 
 the essential part of the cell. It is indeed not to the surrounding 
 membrane, but to the living protoplasm to the formerly undervalued 
 cell-contents that the characteristic capacities of the cell are to be 
 referred. Movement and irritability, assimilation and growth in a 
 word, all the vital phenomena of the organism are dependent on the 
 properties of this protoplasm. 
 
 We cannot retain the slightest doubt on this point when we re- 
 member that there are cells, both among higher and lower organisms, 
 which never become enclosed in a membrane at all, or only at a late stage, 
 but which in their naked membraneless state exhibit the phenomena 
 of life even more conspicuously than the normal membrane-clad cells. 
 
 In these naked cells one can observe, under certain circumstances, 
 and especially in their normal conditions, a peculiar movement. The 
 protoplasm gathers itself at certain convenient points in the form of 
 processes, which grow out under the eye of the observer into lobular or 
 
 8 Ehrenberg, " Die Infusionsthierchen als vollkommne Organismen :" Leipzig, 1838. 
 
 M 
 
178 PROTOZOA. 
 
 finger-like prolongations, which sometimes branch, and, after a time, 
 are again drawn in. With this change of form there has also been a 
 change of position, the cell creeps along by means of its processes, 
 moving slowly, but in a definite direction. Solid particles are thus 
 enclosed by the soft protoplasmic mass, and, if their nature admit of 
 it, may be dissolved or altered. We can even feed the cells in the 
 same manner as Infusoria with particles of .pigment, and watch these 
 as they remain for a while within the body substance. 
 
 It is not difficult to understand the lively interest which these 
 phenomena excited when first closely observed in the white blood- 
 corpuscles of vertebrates. 1 And this was naturally intensified when 
 men became convinced that they had here to do not with a unique 
 peculiarity of these corpuscles, but with a fundamental property of 
 animal protoplasm. Of course some cells may exhibit this pheno- 
 menon in a particularly conspicuous and lively fashion. Thus, only to 
 mention one or two examples, the blood-cells of lower animals (e.g., of 
 Thetis, Fig. 93), according to Haeckel, may be much more easily fed, 
 and exhibit more conspicuous movement, than those of vertebrates, 
 which, for the purposes of observation, require the aid of a warm stage 
 
 FIG. 93. Blood-corpuscles of Thetis, partly with enclosed granules 
 of pigment (after Haeckel). 
 
 or similar appliance. Again, the membraneless eggs of sponges and 
 polyps exhibit amoeboid movements in a most wonderful way. The 
 same is true of segmentation spheres, which often show beautiful 
 " migrating cells," which not unfrequently devour and digest the 
 granules of the yoke, just like independent organisms. 2 
 
 This comparison is all the more necessary since there are numer- 
 
 1 Max Schultze, Archivf. mikrosk. Anat. t Th. i., p. 1 et seq., 1862. Among previous 
 observations I may specially mention those of Lieberkiihn. Mutter's Arckir f. Anat. u. 
 Physiol., p. 14, 1854. 
 
 * See Reichenbach, " Die Embryonalage und erste Entwicklung des Flusskrebses," 
 Zeitschr. f. wiss. ZooL, Bd. xxix., p. 153, 1877 [and also Metschnikoff, Quart. Jmirn. 
 Micr. Sci.< voL xxxiv., p. 89, 1884. W. E. H.]. 
 
PARASITES RESEMBLING NORMAL CELLS. 179 
 
 ous forms among the Protozoa which are hardly distinguishable from 
 these naked cells, except by their free life. Of such animals the best 
 known are the Amoebae (Proteus diffluens of the old zoologists), which 
 are often found in crowds in the sediment of fresh and salt water (we 
 shall speak later of an Amoeba parasite in man), and which in struc- 
 ture and function correspond so closely with the naked cells, that we 
 are accustomed to call the latter " amoaboid " cells, or to describe their 
 movement and method of nutrition by this term. 
 
 Nor are these Amoebae distinguishable from cells in the nature of 
 their reproduction. In both this takes place by division, from the 
 nucleus outwards, through the surrounding protoplasm, and results in 
 the formation of two distinct masses out of the originally simple body- 
 substance. A strictly sexual reproduction has not yet been observed 
 with certainty in any of the Protozoa. 
 
 It is further to be noted that the Amoebae are by no means the only 
 Protozoa which are, in structure and function, interchangeable with 
 the cellular elements of the higher animals. The other groups also 
 contain similar forms in greater or less number. 
 
 This resemblance is not without importance in the history of our 
 science. Even in our day certain parasitic Protozoa (which, as we shall 
 afterwards see, are very numerous) have, on the ground of this resem- 
 blance, been often considered as component parts of their host, and in- 
 versely some cells, in reality belonging to the host, have been classed 
 as parasites. As illustrative of this latter case I need only refer to the 
 so-called " Spermatozoa," which, as is well known, were quite gene- 
 rally ranked as parasitic animals till the time of Kolliker, and were on 
 the strength of this idea frequently credited (even by Ehrenberg, 
 Valentin, and others) with more or less perfect internal organs. So 
 deeply rooted was the notion of the animal nature of these bodies, that 
 it still prevailed even when the existence of living spermatozoa had 
 been long recognised as indispensable to semen capable of fecundation. 
 The only concession in consequence of this fact was to regard the sper- 
 matozoa as " necessary parasites." At that time, too, observers further 
 deceived themselves with the thought that the blood corpuscles might 
 be other similar " necessary parasites " (Mayer). 
 
 It is a still more difficult task, as already hinted, to determine the 
 boundary between parasitic Protozoa and some similar parasites of 
 vegetable origin. With regard to the latter, I have principally the 
 Schizomycetes in view, organisms which, on account of their motile 
 powers, were very generally referred to the animal kingdom as Bacteria 
 and Vibriones, although their nearest relations, the Phycochromacese 
 (Oscillator ia, &c.), containing chlorophyll - granules, are decidedly 
 plants. In former times it was the fashion to call everything an 
 
180 PROTOZOA. 
 
 animal which moved independently, while we, on the contrary, are 
 now acquainted with numerous plants and plant-embryos possessed 
 of the power of locomotion, and are indeed, on the strength of the 
 facts we have mentioned above, inclined to believe that contractility 
 is a general property of (living) organic matter. 
 
 Those Bacteria* which we have mentioned are extremely small 
 rod-like, sometimes spiral, or spherical, bodies, which always abound in 
 decaying organic matter, and multiply so rapidly by transverse division 
 that, as Cohn has calculated, a single individual (150,000 millions of 
 which make up a milligram) may in forty-eight hours produce a mass 
 of half a kilogram, and with good feeding may in three days leave a 
 progeny of 7- million kilograms, at least if those conditions which the 
 calculation postulates ever actually occur. 
 
 They are, however, not only attendant on processes of decomposi- 
 tion and decay, but are able to originate and keep up these and 
 similar processes, acting, like the yeast plants, as oxidising and 
 reducing ferments, taking in or giving out oxygen. Thus they 
 play a most important rdle, some occasioning ordinary putrefaction 
 (Bacterium termo), others the butyric (Bacillus butyris), and others 
 again the lactic and acetic fermentations. The so-called " mother of 
 vinegar " of the latter consists essentially of an organism resembling 
 Bacterium (Mycoderma aceti). 
 
 To this fact, the Schizomycetes owe their high importance in 
 pathology, for they are found not only more or less constantly and 
 plentifully in the excretions and faeces of animals (diarrhoetic dis- 
 charges, purulent matter, alkaline urine, encrustations on the teeth, 
 &c.), but also in the juices and tissues of the body, which must there- 
 fore be correspondingly altered by them. Thus the splenic fever 
 of our domestic animals depends, as we now know with the greatest 
 certainty, on the presence and growth of Bacteria (Bacillus anthracis) 
 which infect the blood, 2 and which, on transference to man, may 
 
 1 Of the voluminous literature on the subject of Bacteria I will only mention Cohn's 
 researches, " Beitrage zur Biologic der Pflanzen," Hefte ii., in., 1872 and 1873. 
 
 2 Through the investigations of Koch and Cohn (lor., cit. ), we now know the whole life- 
 history of the usually motionless splenic fever Bacteria. As long as they are contained 
 in the living host, they remain unchanged, but in the blood or suitable juices of the dead 
 animal they grow out into a long unbranched thread, which develops numerous small 
 shining spores. After these have been carried into a living body, they give rise 
 to Bacteria again, which at once begin to divide. This transference may not take 
 place for a long time, for the spores are able, without loss of their reproductive capabilities, 
 to lie dried up for years, or to remain whole months in putrefying fluids, or even to en- 
 dure alternately damp and dry environment. The transmission is probably effected by 
 external contact, the spores being carried into wounds, perhaps along with dust. No in- 
 fection is possible internally from the stomach. If the blood and tissues of the dead 
 animal are rapidly dried, so that the Bacillus is unable to form spores, then the possibility 
 uf infection only lasts a few weeks. 
 
SCHIZOMYCETES. 181 
 
 give rise to malignant pustule: similarly pyaemia, small-pox, diph- 
 theria, and other so-called " contagious diseases " are occasioned by 
 Bacteria of extreme minuteness (Micrococci). l Even in recurrent fever 
 the presence of a spirally twisted Bacterium (Spirillum) in the blood 
 is a constant phenomenon. According to Koch, cholera is also 
 caused by a Bacillus (B. comma). 2 Since our experience of the patho- 
 logical nature of these structures is daily widening, we can understand 
 how many modern pathologists would refer the infectiousness of all 
 such diseases to the presence of active Schizomycetes. The old 
 doctrine of " Contagium vivum" (p. 121) is thus resuscitated in a 
 changed form. 
 
 If we inquire without prejudice into the reasons which lead us 
 to refer the Schizomycetes to the vegetable kingdom, in spite of their 
 animal-like nutrition and locomotion, we can give no other answer 
 than this, that they belong to a phylogenetic series, which leads in 
 uninterrupted succession to indisputable plants. The properties which 
 they themselves possess hardly suggest a reason for separating them 
 from the Protozoa, for the Schizomycetes are organisms of small size 
 and simple structure, without cellular organs or tissues, and with 
 exclusively (or at least predominantly) asexual reproduction. They 
 are, in other words, creatures which in their organization do not (or at 
 most only slightly) transcend the differentiation of a simple cell, and in 
 fact are sometimes mere masses of protoplasm. 
 
 From the phylogenetic point of view, we can not only define the sys- 
 tematic position of the Schizomycetes, but are also enabled to restrict 
 the Protozoa to the three classes of Ehizopoda, Gregarinida, and In- 
 fusoria. These also are, of course, not wholly without their points of 
 contact with certain vegetable organisms, but are on the whole more 
 closely linked to the animal kingdom, and in their highest representa- 
 tives the Infusoria are certainly of the nature of animals. 
 
 The peculiarities of these three groups lie for the most part in 
 their modes of nutrition and motion, but many other differences exist 
 in their reproductive processes and general organization. The Ehizo- 
 poda, for example, with their naked mass of protoplasm, move by 
 means of rapidly changing lobose or filiform processes (so-called 
 " Pseudopodia "), which we have already seen in the Amoeba, one of 
 
 1 In regard to the organisms of the small-pox lymph, see Cohn, Archiv f. pathol. AnaL, 
 Bd. lv., p. 229, 1872 ; and on those of diphtheria, fcce Oertel, Deutsch. Archiv f. Tclin. 
 Mcd., Bd. viii., p. 242, 1871; also Klebs, " Beitrage zur Kenntniss der pathogenen Schi- 
 zomyceten :" Prag, 1874. 
 
 2 [For an account of the controversy regarding the comma Bacillus, see Klein, " Micro- 
 Organisms and Disease," Second Ed., London, 1885 ; also various papers in the Lancet and 
 liritish Medical Journal, 1884 and 1885 ; and, for a brief summary of the question, Nature, 
 vol. xxxi., p. 97, 1885, and Lankester, ibid., p. 168. W. E. H.] 
 
182 KHIZOPODA. 
 
 the members of this group ; the Infusoria, on the other hand, possess 
 a permanent locomotor apparatus in the form of cilia ; and the Gre- 
 garinida glide forwards in a more worm-like fashion by the contraction 
 of their larger body-mass. Further, the Rhizopoda and Infusoria feed 
 on solid, or at least somewhat firm food, which either (Rhizopoda) 
 simply sinks into the protoplasm, or is ingested by means of a special 
 mouth (Infusoria), while the Gregarinida are supplied with fluid food 
 exclusively by endosmosis through the enveloping cuticle. The Gre- 
 garinida live wholly as parasites, and therefore in conditions which 
 render the presence of either a temporary or permanent mouth un- 
 necessary. It is equally intelligible that the mouth is, as we shall 
 see, wanting even in some parasitic Infusoria (species of Opalina). 
 
 The term Gregarinida must, however, be restricted to those forms 
 which are found usually in crowds in the alimentary canal or other 
 viscera of some lower animals, especially insects arid worms, and which 
 have at the first glance a superficial resemblance to microscopic Nema- 
 todes, as which indeed they were formerly described. The name can- 
 not be extended to allied organisms found parasitic on higher animals, 
 for these differ in many ways from the true Gregarines, both in ap- 
 pearance and in life-history, though closely linked to them by the 
 very characteristic reproduction by hard -shelled germs (the so- 
 called " Pseudonavicelhe," or " Psorospermiae "). I will therefore 
 introduce the term " Sporozoa " to denote the forms above referred to. 
 
 All the three classes have, as the following survey will show, 
 representatives parasitic in man. 
 
 CLASS I. RHIZOPODA. 
 
 Protozoa, consisting of a memfoaneless mass of protoplasm, which 
 forms lobose, finger-like, or filiform, and often branched pseudopodia, 
 and taking in solid food without having a permanent mouth. Only a 
 few forms are naked, the majority 2>ossess cither a simple chitinous or a 
 hard calcareous or siliceous skeleton, which is provided with more or less 
 numerous openings for the protrusion of the pseudopodia, or may not 
 unfrequently consist simply of single needles. Reproduction takes place 
 partly by simple division, partly by actively moving germs produced 
 within the body-substance. 
 
 In the simplest forms, the so-called " Monera," the body consists 
 of an apparently non-nucleated mass of protoplasm, without further 
 recognisable differentiation. At most, and that after rich feeding, the 
 body is seen to be studded with small granules, which are only absent 
 in the outermost portion. But as a rule, in the Rhizopoda, a distinct 
 
PSEUDOPODIA AND SKELETON. 183 
 
 nucleus can be further distinguished, which may either remain simple, 
 or, with an increase of size, divide, and that often into a considerable 
 number of nuclei. Again, a varying number of vacuoles may be ob- 
 served, which sometimes exhibit a 'conspicuous and even rapid con- 
 traction. In the higher forms, the protoplasm becomes differentiated 
 into an outer layer, and a central substance which encloses the nuclei, 
 and may itself be enclosed by a porous membrane (Eadiolaria). At 
 the same time the body assumes a firmer consistency, and a stable, 
 generally spherical, form, having, however, an appearance varying 
 according to the degree of contraction, and generally showing a state 
 of activity in the pseudopodia, which are protruded as lobose processes, 
 almost as if flowing from the body mass. The form and nature of 
 the pseudopodia vary generally according to the consistency of the 
 protoplasm ; their rigidity and fineness are usually proportional to the 
 firmness of the body-substance. The movement of granules, which is 
 often to be observed in most wonderful fashion on the thin Pseudo- 
 podia, is sufficient to prove that their substance, even when in appar- 
 ent rest, is the seat of a continual molecular displacement. 
 
 We need say the less about the skeleton of the Ehizopoda, since 
 that has only to be considered in the free-living forms, which only 
 interest us here, in so far as they serve more fully to illustrate the 
 general structure of the Ehizopoda. The Ehizopoda can evidently 
 live only in a moist environment, indeed almost wholly in water, but 
 are also found in the earth, and particularly in the thin moist moss 
 or lichen-covered surface of trees and rocks. The skeleton of the 
 fresh- water forms is usually of a simple membranous nature, 
 forming a sort of shell, out of the opening of which the animals pro- 
 trude their Pseudopodia. In the marine forms, the skeleton acquires 
 a firmer character by taking in lime or flint, and is frequently of ex- 
 traordinary beauty. This is specially true of the Eadiolaria, which, 
 with their needles and lattice work of flint, are among the most 
 beautiful of microscopic objects. The calcareous skeletons are gene- 
 rally coarser and heavier, and lie quiescent with their occupants among 
 foreign substances ; while the Eadiolaria, with their delicate skeleton 
 and the radiating meshwork of protruded Pseudopodia, are often 
 found floating in the water. Like the chitinous shell, the calcareous 
 skeleton has often only a single opening, but in the majority of cases 
 it is perforated by countless small pores through which the Pseudo- 
 podia issue (hence the name " Foraminifera "). The Polythalamia 
 have a number of united chambers, which increase in number with 
 the increasing size of the body. The closed form and immoveable 
 walls of the house indeed necessitate a new building if the body is 
 to increase in size. 
 
184 RHIZOPODA. 
 
 These chambers in some species lose their continuity, and, retain- 
 ing their contents, lead an isolated life ; and this may be the more 
 readily regarded as a form of asexual reproduction, since the single- 
 chambered fresh-water Rhizopoda also not unfrequently protrude 
 their contents to a greater or less extent out of the chamber, and by 
 the secretion of a shell form a new organism. 
 
 Simple division (which, however, when the portions are of unequal 
 size, looks more like budding) is apparently very common among the 
 Rhizopoda. But we further find a second kind of reproduction, in 
 which the body-mass, like the yolk of a fertilised ovum, falls into a 
 varying number of pieces, each of which then becomes a distinct 
 organism, and often finds its way to the exterior in the temporary 
 form of a swarm-spore, provided with a single cilium. As an ante- 
 cedent to this process, the naked so-called Amoebae first surround 
 themselves with a membranous covering, which encloses the body 
 like a capsule ; but this may be also secreted under other circum- 
 stances, e.g., in the scarcity of water. Protected by this capsule, the 
 creatures can undergo desiccation without danger, just as do the eggs 
 of the Nematodes, previously mentioned (p. 53). 
 
 In those Foraminifera which have tests, the fonnation of the 
 brood takes place in the several chambers, inside which the young 
 are, in many species, surrounded by a shell, so that on the rupture of 
 the enclosing test they issue forth resembling their parents. 
 
 The swarm-spores of Radiolarians arise in the central capsule 
 that is, in the nucleated central substance. 
 
 It was demonstrated as early as 1859, by Lainbl, that the Rhizo- 
 poda included forms parasitic in man. 1 In the intestinal mucus of a 
 child who died of enteritis, there were observed not only small naked 
 amoeboid organisms, 0'004 to 0'006 mm. in diameter, but also shell- 
 bearing Diffluyiw and Arcellcc (O'Ol to O'OIG mm.), which are found 
 normally only in ponds and ditches. The representation which Lambl 
 gives of these creatures is, however, so incomplete, that their identifi- 
 cation seems in the highest degree suspicious. At any rate, such a 
 discovery, so long as it remains uncorroborated, can hardly be regarded 
 as established. But since we know from other quarters of the occur- 
 rence of a parasitic Amoeba in man, it is a reasonable supposition that 
 at least some of the observed bodies were indeed nothing else than 
 parasitic Rhizopoda. 2 Amcebce are also to be observed as parasitic in 
 various conditions in other higher and lower animals ; 3 but only 
 
 1 " Aus dem Franz- Joseph-Kinder-Spitale," Bd. i., p. 363, Taf. xviii. 
 a Apart from the loose or otherwise altered epithelial cells, others might be referred 
 to the group of Monads. 
 
 3 Thus, for example, Lieberklihn reports the occurrence of A mocha in the intestine of 
 
AMOEBA. 185 
 
 the naked and not shell-bearing forms of Rhizopoda have been found. 
 The latter we must, for other reasons, regard as exclusively confined 
 to water or damp earth. 
 
 We must again, however, remember that fragments of cellular 
 tissue may be easily confounded with true Amoebae, and many so- 
 called Amoeba may be only a developmental stage of entirely different 
 animals. We know even of active Rhizopod-like fungi (the so-called 
 Myxomycetes'), which, in their youth, are exactly like Amoebce 1 (Myxa- 
 mcebce), and may, under certain circumstances, live for a long time as 
 such. 2 
 
 Amoeba, Ehrenberg. 
 
 Auerbach, " Ueber die Einzelligkeit der Amceben," Zeitschr. f. wiss. Zool, Bd. vii., 
 p. 365, 1855. 
 
 Naked Ehizopoda, with a richly granular protoplasmic body-sub- 
 stance, surrounded by a thin hyaline layer, and enclosing, besides the 
 nucleus, one or more contractile vesicles. The Pseudopodia are finger- 
 like, sometimes lobose, processes, which become full of granules when they 
 attain a certain size, and which vary in number and breadth according 
 to the consistency of the body. 
 
 The form of the body may be generally described as spherical ; 
 but this undergoes during life a continual Protean change, as the 
 animals flatten themselves out for movement, and then send out 
 pseudopodia, now here, now there, indifferently. The size and struc- 
 ture of the latter differ sometimes very characteristically in the 
 different species. When the protoplasm has only a comparatively 
 slight consistency, the animals seem almost to flow along on their 
 lower surface. The nature of the food varies according to circum- 
 stances, but in the free-living forms consists mainly of parts of plants. 
 These are enclosed by the movements of the protoplasm, and are 
 digested, the undigested residue being expelled by any part of the body 
 indifferently. The only mode of reproduction as yet distinctly ob- 
 served 3 is that of simple division, which is completed in a short time, 
 
 the frog (Mutters Archivf. Anat. u. Physiol., Bd. viii., p. 12, 1854). They are sometimes 
 found in considerable numbers, and exhibit a somewhat rapid motion. Similarly, Walden- 
 berg found amo3boid animals in the intestinal canal of the rabbit, and once even inside an 
 epithelial cell (Archivf. pathol. Anat., Bd. xl., p. 438, 1867). Amoeboid parasites are also 
 not unfrequently found in the intestinal canal of insects, such as beetles, &c. 
 
 1 See the classic investigations of de Bary on Myxomycetes, Zeitschr. f. wiss. ZooL, 
 Bd. x., p. 88, 1859 [and more recently Zopf, " Die Spaltpilze :" Breslau, 1883. W. E. H.] 
 
 2 According to Cienkowsky, Archiv f. milcrosk. Anat., Bd. xii., p. 15, 1876. 
 
 3 [More recently it has been demonstrated by the investigations of Maggi, Grassi, 
 Brass, and others, that Amoeba not only divide, but also, 'after encysting form swarm - 
 spores, which resemble Monads both in appearance and in movement. R. L.] 
 
186 
 
 AMCEBA COLI. 
 
 and, under favourable conditions of nutrition, rapidly repeated. 
 Under some circumstances an encystation takes place, when the 
 animal draws itself together into a sphere, and secretes a substance 
 originally mucous in nature. 
 
 Amoeba coli, Losch. 
 
 Lb'sch, "Massenhafte Entwickelung von Amoeben im Dickdarm," A rchiv f. pathol. 
 Anat., Bd. Ixv., p. 196, Taf. x., 1875. 
 
 The body measures from 0*02 to 0*035 mm., is of a somewhat fluid 
 and coarsely granular nature, and forms usually only one or a few Uunt 
 and broad processes. These arise suddenly, and are not unfrequently 
 drawn in as suddenly, giving the otherwise roundish body a sometimes 
 oval, sometimes pear-shaped, or even irregular form. In the interior, 
 besides granules and food, a clear round nucleus may be recognised, 
 as also several vacuoles, sometimes irregular in shape and of varying size. 
 
 
 FIG. 94. Amoeba coli in intestinal mucus, with blood corpuscles, Schizoniycetes, 
 and similar bodies (after Losch ). 
 
 The A mceba thus shortly characterised (Fig. 94) has hitherto been 
 only once observed, namely in St. Petersburg, in a peasant who 
 suffered from an ulcerative inflammation of the large intestine. 1 It 
 
 1 [Grassi states (Gazctta med. Ital Loinb., No. 45, 1879) that he has observed Amoeba 
 coli six times in Italy. The parasites were always present only in small numbers, and 
 in persons whose health had undergone no change. Cunningham also, who not unfre- 
 quently observed the occurrence of A moela in the human intestine, and still more often in 
 the cow and the horse, is disposed to attribute to it no special pathogenic significance. 
 The parasite occurs, however, in certain diseases of the intestine, especially in such as are 
 characterised by alkaline excreta and in cholera, and its presence may then be referred 
 to the specially favourable vital and developmental conditions found under such circum- 
 stances. Cunningham further holds that Flagellata parasitic in man are to be regarded 
 
ORGANIZATION AND VITAL PHENOMENA. 187 
 
 was abundantly found in the ill-smelling, thin, fluid stools, which also 
 showed the usual contents of dysenteric stools i.e., besides remains 
 of food red and white blood corpuscles, detached intestinal epi- 
 thelium, and cell fragments, and a great number of bacteria, micrococci, 
 and monads. There was, however, no possibility of confounding the 
 Amoeba with other structures. In appearance, size, and mode of motion, 
 they were sufficiently distinguished from the surrounding elements. 
 
 Although this case stands as yet alone, we can well believe that 
 the occurrence of parasitic Amcebce in similar intestinal diseases is 
 both frequent and widely distributed. I am corroborated in this sup- 
 position, not only by the above-cited and questionable observation of 
 Lambl, but also by an oral communication from my esteemed friend 
 Dr. Sonsino, in Cairo, who found large numbers of an equally unde- 
 niable Amoeba in the intestinal mucus of a child who had died of 
 dysentery. Its size was from 8 to 10 times that of the blood cor- 
 puscles. Since the forms observed by Losch were only 5 to 8 times 
 as large as the red blood corpuscles, we may perhaps conclude that 
 the Egyptian Amoeba was of a different species. Steinberg also alleges 
 the discovery of an Amceba (A. buccalis) in the mucus covering the 
 teeth of man (vide postea). 1 
 
 One can form some approximate conception of the immense 
 number of Amoebce living together in the intestine when one learns 
 that Losch often saw, with a magnifying power of 500, from sixty to 
 seventy specimens in the same field of vision ; and Fig. 94 (repro- 
 duced as closely as possible from nature) shows by no means the 
 most thickly crowded portion. 
 
 The movements which first attracted the attention of the ob- 
 server are described as follows : " On any part of the surface of the 
 body indifferently, a small, roundish, transparent, glassy projection 
 appears, sharply divided from the rest of the granular protoplasm. 
 This is either rapidly retracted, or, increasing quickly in size, it forms 
 eventually a finger-like process, whose length approximates to the 
 diameter of the rest of the body. This process is finally drawn 
 in again, only to reappear at another point ; or it may be that the 
 granular protoplasm suddenly flows into it and fills it up. In 
 this way the form of the whole animal changes, it becomes oval, 
 elongated, or, where there are several processes, irregular. The 
 processes are constantly blunt, never filiform, or running to a point. 
 
 as developmental stages in the life -history of a Myxomycete, which he calls Proto- 
 myxomyces coprinarius ("On the Development of certain Microscopic Organisms occurring 
 in the Intestinal Canal," Quart. Journ. Micr. Sci., vol. xxi., pp. 234-290, 1881). K. L.J 
 1 [Grassi speaks also (loc. cit.) of an Amceba dentalis observed by him in three cases. 
 It is said to resemble A. coli, and, like this, to become quiescent at low temperatures 
 (below 25 C.). R. L.] 
 
188 AMCEBA COLL 
 
 Their formation, as compared with the changes of a blood corpuscle, 
 is characterised by great rapidity, for they are sometimes protruded 
 and retracted four or five times in a minute. They arise, indeed, so 
 suddenly as to produce the impression that the protoplasm flows out 
 at a circumscribed portion, forming a little drop of mucus. The 
 animals generally keep to one place during these movements, but 
 sometimes they creep slowly about, first sending out a long trans- 
 parent thread, then allowing the granular protoplasm to flow into this, 
 and, lastly, drawing the rest of the body forwards. These changes of 
 position take place comparatively slowly, the animals hardly advancing 
 the length of their body in a minute." 
 
 The nucleus presents a globular, transparent, colourless, or faintly 
 yellow appearance, and varies in diameter from (V0048 to 0*0069 mm. 
 It has but slight consistency, often changing its shape somewhat with 
 the movements of the parasite, and becoming sometimes more oval 
 or somewhat lengthened out, but regaining its original form on the 
 withdrawal of the pressure. In quiescent specimens it lies more in 
 the centre of the granular protoplasm, and is therefore observed only 
 with difficulty ; in actively moving forms it may occupy any position 
 throughout the body, and often lies near the surface of the body. In 
 the interior one may distinguish a nucleolus of very varied size and 
 refractive power. In individual cases its diameter is half that of 
 the nucleus. It is transparent, but in the smaller specimens shows 
 a dark contour, and has such power of refracting light that it some- 
 times looks not unlike a fat granule. The vacuoles in the protoplasm 
 are also of very varied size. Most of them are larger than the nucleus, 
 but some are only half as large ; exceptionally, one sometimes finds 
 them half as big as the whole animal. Their number varies from one 
 or two to six or eight, or even more, but the smaller numbers more 
 frequently occur. In exceptional cases they seem to be wholly 
 absent, and only appear after the addition of water. After prolonged 
 observation, a distinct change of form is sometimes to be observed. 
 They sometimes become rather smaller, sometimes larger, -and, as the 
 Amceba moves, may assume an oval or long bean-shaped, or even 
 irregular form. Distinct pulsations cannot, however, be observed. 
 
 Besides the component parts, various foreign substances are some- 
 times found embedded in the protoplasm, especially Bacteria, Vibriones, 
 Micrococci, and chains of Mycothrix ; and exceptionally larger bodies, 
 such as red and white blood corpuscles, nuclei of detached cells, starch 
 grains, and other substances found in the intestine. After the ap- 
 plication of an enema of vermilion, given to the patient to test the 
 ingestive power of the Amoebce, particles of the pigment were to be 
 seen in their interior. 
 
MODE AND RESULTS OF INFECTION. 189 
 
 Unfortunately nothing is known of the life-history of Amceba coli. 
 We do not even know its mode of reproduction. But the very 
 abundant occurrence of the parasite leaves no doubt that reproduction, 
 and that a most prolific one, does take place within the intestine. 
 For in the hospital, where a continued supply of the parasite from an 
 external source was hardly possible, no diminution was perceptible, 
 though the daily voiding went on for four months. The most natural 
 supposition is, of course, that the reproduction took place by division, 1 
 as has been directly observed in other Amcebce ; see especially F. E. 
 Schultze's observations on Amoeba polypodia. 2 
 
 As regards the mode of transmission, we are of course left to 
 hypotheses, which are all numerous as they may be without ex- 
 ception destitute of foundation, since we do not know whether the 
 Amceba coli lives exclusively in the intestine, or is parasitic only 
 accidentally. There are, indeed, some free- living species which closely 
 approach this form in their appearance and mode of motion. Losch 
 has, in this connection, drawn attention to . Amceba princeps, Auerb., 
 but it seems to me to resemble still more closely A. Maginia, lately 
 described by v. Mereschowsky. 3 This suggestion receives some proba- 
 bility from the fact that this form is found " in great abundance in 
 the sand and mud at the bottom " of the Jelaginic ponds near St. 
 Petersburg, in the same locality, that is, in which the above-men- 
 tioned patient had presumably become infected with his parasites. 
 
 The patient had lived a most miserable life, sleeping in half-built 
 barracks, protected neither from wind nor rain, and was mainly occu- 
 pied in dragging logs out of the water. It is, therefore, likely that he 
 
 1 [In view of the above-mentioned formation of spores in Amoeba, one can hardly help 
 believing that this process plays an important part in the reproduction of parasitic forms, 
 and this so much the less, since Grassi has published his investigations upon a species 
 (Amceba pigmentif era) parasitic on Sagitta (Rendiconto Instit. Lomb., vol. xiv., 1881) ; and 
 since Brass ("Die thierischen Parasiten des Menschen," Cassel, 1884) and others have 
 observed the same process in the intestinal A mcebce of the mouse and frog. 
 
 Cunningham also observed an encapsulation in the case of his Protomyxomyces, when 
 cultivated in the free state (in alkaline cows' dung). But within these cysts were developed, 
 not swarm-spores, but resting-spores, with a cuticular envelope, which either remained in 
 groups or separated from each other. From these spores Cunningham believes, though he 
 has not actually observed it, that the ciliated intestinal parasites arise, which in their 
 turn, after manifold variations, give rise to resting-spores again. R. L.J 
 
 2 Archiv f. mikrosL Anat., Bd. xi., p. 592, 1875. 
 
 * Archiv f. mikrosL Anat., Bd. xvi., p. 204, Taf. xi., Figs. 29 and 30, 1878. The 
 description accompanying the figures runs as follows: "The form of the body varies 
 exceedingly. The body sends out short round processes, but the movements are not due 
 to these, but to the Amceba flowing en masse. The contents consist of coarse and fine 
 granules, both kinds being present in abundance. The ectoplasm is distinctly separated 
 from the endoplasm. Besides the nucleus there are also some vacuoles visible, which con- 
 tract very rapidly in the interior of the body. The consistence is fluid, the movement 
 rapid. The diameter varies from 0'02 to 0'04 mm." 
 
190 AMCEBA COLL 
 
 had often drunk impure and muddy water ; but I am not at all in- 
 clined to identify his parasite with the above free-living form, for, in 
 spite of much resemblance, there are also many differences (in size 
 and behaviour of the vacuoles) between them. 
 
 The disease of the patient had, on the whole, the appearance 
 of an intense and persistent dysentery, and on post mortem ex- 
 amination the large intestine was seen to be violently inflamed, and 
 in some places, especially in the lower regions, ulcerated. To the 
 important medical question whether the parasite stands in a direct 
 causal relation to the disease or not, our author gives an unreserved 
 affirmative answer. Losch would at least insist that the Amcebw 
 aggravate the inflammation, and do not allow the ulcers to heal. He 
 supports his opinion partly by referring to the immense number of 
 the Amoebae, which, by their uninterrupted movements, could not but 
 cause a mechanical irritation of the diseased mucous membrane, partly 
 by referring to the fact that during the whole course of the illness 
 there was an undeniable relation between the number of the parasites 
 and the intensity of the inflammation. Further, only the systematic 
 use of quinine enemas, 1 which caused the parasites for a time almost 
 wholly to disappear, had any effect in alleviating the malady. Pleurisy 
 afterwards set in, followed by pneumonia, and death finally super- 
 vened, with all the phenomena of complete anaemia and exhaustion ; 
 and it was only in these last stages that the Amcebce wholly disap- 
 peared, and the diarrhoea consequently ceased. 
 
 The convincing argument in favour of Losch's opinion is the result 
 of an experiment which he made. In order to get some direct evi- 
 dence of the pathological import of these parasites he injected three 
 dogs per os et anum with from one to two ounces of fresh stools con- 
 taining these Amoebae, and repeated the injection on three successive 
 days. A fourth dog was similarly treated after an intense intestinal 
 inflammation had been produced by enemas of croton oil This was 
 meant to show whether the Amoebae, were able to aggravate an inflam- 
 mation already existing. 
 
 Only one of the experiments gave any positive results. One of 
 the first three dogs, after recovering from the digestive disorder 
 (vomiting and diarrhoea) which first appeared, seemed to be perfectly 
 healthy ; but eight days after the last injection a small mucous mass 
 of about the size of a pea, and a bloody colour, was found in the 
 otherwise normal excrement, and this on microscopic examination 
 exhibited a great number of living Amoebae. In the course of the 
 next few days the number of Amcebce thus voided rapidly increased, 
 
 1 According to the experimental result of Binz, corroborated, indeed, by the above 
 case, quinine is an efficient poison for organisms consisting of simple protoplasm. 
 
SPOKOZOA. 191 
 
 though the general state of health remained the same, and showed no 
 further abnormal phenomena. Since the elapse of two weeks resulted 
 in no further change, and the excrement remained firm and normal in 
 spite of the associated mucus, the dog was killed eighteen days after 
 the first injection. On examination the mucous membrane of the 
 rectum was found in some places reddened, irregularly swollen, covered 
 with viscous blood-stained mucus, and superficially ulcerated in three 
 places. The ulcers were roundish, of 4 to 7 mm. in size, and sur- 
 rounded by swollen and exceedingly hyperaemic mucous membrane. 
 Their base was irregular, and had a dark red appearance. The sub- 
 mucosa below was hypersemic, swollen, moist, and turbid. The mucus 
 in the rectum and in the ulcers was thickly crowded with Amoebae, 
 which differed in no respect from the injected parasites. The mucous 
 membrane of the large intestine was normal, nor did the other organs 
 exhibit any pathological character. 
 
 This experiment proves at least that these Am&bce, if abundantly 
 developed in the intestine, may give rise to violent irritation of the 
 mucous membrane, and cause not only hyperaemia and increased 
 formation of mucus, but also an intense inflammation, sometimes 
 aggravated by ulceration. 
 
 CLASS II. SPOEOZOA. 
 
 [Davaine, " Leons sur les Sporozoaires :" Paris, 1884. R. L.] 
 
 Unicellular parasites of definite form, without pseudopodia or cilia, 
 but covered by a smooth, more or less firm, cuticle. At the anterior end 
 there is not unfrequently an organ of attachment, like a proboscis or 
 cushion. Their movements are inconspicuous, worm-like, or slightly amoe- 
 boid. They live wholly as parasites, and receive their food by endosmosis. 
 Reproduction takes place by more or less hard-shelled spores (Pseudo- 
 navicellce, Psorospermice), which are formed in the interior of the adult, 
 sometimes in very great numbers. Occasionally they appear gradually, 
 but more often simultaneously, and then after the attainment of maturity 
 and encapsulation. In these spores there develop, sooner or later, a 
 varying but usually small number of sickle-shaped bodies, which, after 
 creeping out, become new parasites. In other cases the contents of the spore 
 are collected in a single amoeboid embryo. 
 
 The most familiar examples of these Protozoa are the Gregarines 
 (Fig. 95), which stand highest in their organisation and functional 
 activity, and indeed represent a special group. They are, so far 
 as we know, parasitic only in invertebrates, especially in insects and 
 
192 
 
 SPOROZOA. 
 
 worms, and usually occur associated in great numbers. 1 In certain 
 animals, and especially in omnivorous species (Tenebrio, cockroach, 
 earthworm, &c.), they are almost constant, so that one can 
 hardly examine a specimen without finding Gregarines. They are 
 
 harboured sometimes in the intestine, 
 as in insects, sometimes in other organs, 
 as in the testes of the earthworm, some- 
 times in the body-cavity. 
 
 The body of the Gregarine 2 is more 
 or less extended, and often saccular. 
 The intestinal parasites are very con- 
 stantly provided with a pad or pro- 
 boscis like, sometimes even hooked, 
 process, which serves as an organ of 
 attachment, and if in the form of a 
 sucker, may connect two animals to 
 gether (Fig. 95, B). The protoplasm 
 is more or less granular, according to 
 the age and size of the parasite. It 
 encloses a large vesicular nucleus with 
 a nucleolus, and is surrounded by a 
 
 FIG. 95. Gregarines. (A) Mono- 
 
 cyatis agilis, from the testes of 
 
 the earthworm ; () Gregarina porous Cuticle, under which may be SOIlie- 
 
 cuneata, from the intestine of *. . * 
 
 Tenebrio; (C) Styiorhynchus oK- times distinguished a thin, clear, some- 
 gacantkus, from the intestine of a times striated, outer layer. The formation 
 
 of spores takes place at the close of the 
 
 individual development, when the animal has attained its full size, 
 and has lost its attaching apparatus. It draws itself together into 
 a ball, and encysts singly or in pairs. In the latter case, after 
 
 FIG. 96. Encapsuled Gregarines. (A) After conjugation ; 
 (B) After formation of pseudonavicellae. 
 
 1 Hence the name Gregarina, from "Grex," a herd. 
 
 2 For an account of the Gregarines, properly so called, see especially the researches of 
 Frantzius, " Observations qusedam de Gregarinis," Wratislav, 1846; Stein, " Ueber 
 die Natur der Gregarinen," Mutter's Archiv f. Anat. u. PhysioL, p. 182, 1848 ; and Aime* 
 Schneider, " Contribut. a 1'hist. des Gregarines," Archiv. d. Zool. cxptr., t. iv., p. 493 et 
 seg.,1875. 
 
FORMATION OF THE PSEUDONAVICELLA. 193 
 
 the conjugation has taken place, the two bodies are still distin- 
 guishable within the wall of the cyst (Fig. 96, A), after this the 
 contents, either as a whole or in their outer layer, produce by a 
 sort of peripheral segmentation a large number of small balls, which 
 become the spindle-shaped Pseudonavicellae after the secretion of a 
 hard shell (Fig. 96, B). 
 
 We cannot here discuss the numerous more or less striking differ- 
 ences in the form and size of these spores. We must, however, point 
 out that the cysts sooner or later find their way to the exterior (though 
 often, as in the earthworm, only after the death of their host), and 
 there set the spores free. For this last purpose there are sometimes 
 special arrangements in the cysts, such as canals and " discharging 
 bombs," which are formed out of that portion of the contents which 
 was not devoted to the manufacture of spores. 1 
 
 Each Pseudonavicella contains a granular mass, which, after secret- 
 ing a clear plasma, very soon gathers itself into a central mass. 
 According to Lieberkiihn, who bases his statement on investigations , 
 into the Gregarine of the common earthworm (Monocystis agilis s. 
 lumlrici), this mass forms an amoeboid creature, which breaks out of 
 the Pseudonavicella, remains for a while in the body-cavity of its host, 
 and finally becomes a Gregarine by the assumption of a cuticle. 2 
 
 It is, however, hardly doubtful that Lieberkiihn has fallen into 
 error. He has confused amoeboid masses found in the perivisceral 
 fluid of the earthworm, and representing blood or lymph corpuscles 
 with stages in the life-history of the Gregarine. He has also further 
 erred in regard to the changes which the contents of the Pseudo- 
 navicellse undergo, for, especially in the case of Monocystis luiribrici, it 
 is certain, as Schneider has stated, that the development is quite 
 otherwise. The contents, instead of forming an amoeboid body, fall into 
 about six little clear sickle-shaped rods. These distribute themselves 
 equally over the two halves of the Pseudonavicella, and the rest 
 of the granular mass collected into a ball lies between them (" nucleus 
 de reliquat"). (Fig. 97, A-C.) The same changes take place also in 
 many other Gregarines, usually, however, not in the original host, 
 but externally. The expelled cysts may be kept alive for some weeks 
 in water (Fig. 97, D-F). 
 
 Since Schneider succeeded, after treatment with osmic acid, 
 in demonstrating the presence of a nucleus in the sickle-shaped 
 bodies, he supposes that they are already true Gregarines, and that 
 they pass without essential change, by growth, accumulation of 
 
 1 Aime Schneider, " Sur un appareil de dissemination des Gregarines," Comptts 
 rendus, t. Ixxx., p. 432, 1875. 
 
 2 " Evolution des Gregarines/' Mem. couronn. de VAcad. de Belyc, t. xxvi., 1855. 
 
 N 
 
194 SPOROZOA. 
 
 granules, and secretion of a firm cuticle, into the adult Gregarines. 
 With this agree the observations of A. Schmidt, 1 who found the first 
 stages ofMonocystis lumbrici as extremely small, transparent, membrane- 
 less creatures within the spermatic vesicles of the host, and who also 
 
 FIG. 97. Pseudonavicellae with germinal rods in their interior; A-C, of Monocyatis 
 ogilis; D and E, of Urospora nemertidis; F, of Gonospora tcrelellc? (after Aim6 Schneider). 
 
 attempted to follow their further development. Such a Gregarine is 
 sometimes so small that it hardly attains a third of the diameter of 
 the vesicle, but is in other cases so large as completely to fill it, and 
 even to distend it beyond its usual dimensions. 2 The sperm cells, 
 which are situated outside the infected vesicles, have obviously a some- 
 what abnormal development in consequence of parasitism, showing, 
 instead of long threads, a short tufted fringe, which persists for a 
 while on the periphery of the young Gregarine, 3 and is only thrown 
 off after they creep out. 
 
 According to the younger van Beneden, 4 the development of Gre- 
 garina gigantea, whicli lives in the intestine of the lobster, and some- 
 times attains a length of 16 mm., is somewhat less direct. Instead 
 of passing directly into the Gregarine form, the ameboid mobile stage 
 produces two long bud-like processes, which then pass into Gre- 
 garine forms, which are at first destitute of a nucleus. 
 
 We must leave it to the future to decide between these contradic- 
 tory opinions, 5 and will only further state that, according to Schneider, 
 there are also Gregarines whose Pseudonavicellse, instead of the 
 
 1 " Beitrag zur Kenntniss der Gregarinen und deren Entwickelung," Alhandl. d. 
 Senkenberg. Gesellsck., Bd. i., p. 168 et seq., 1854. 
 
 2 See the confirmatory researches of Lieberkiihn, Mutter's A rchiv /. Anat. u. Physid., 
 p. 509, 1865. 
 
 3 Such structures have given occasion to the opinion that there were (in the earth- 
 worm) Gregarinw provided with bristles. 
 
 4 "Recherches sur 1' evolution des Gregarines," BuU. Acad. roy. Belg., t. xxxi., 1871. 
 [Translation, Quart. Journ. Mirr. Sci., N. S., vol. xi., p. 242, 1871 ; also Ann. Mag. Nat. 
 Hist., ser. 4, vol. x., p. 309, 1872. W. E. H.] 
 
 6 [The number of these rival theories has recently been increased by Ruschhaupt 
 (Jenaisch. Zeitschr., Bd. xviii., p. 713, 1885), who does not regard the sickle-shaped bodies 
 in the Pseudonavicellse of the Gregarines as true nuclei, but rather considers that the 
 young Gregarines arise from the general mass of the PseudonaviceHae. R. L.] 
 
PSOROSPERM-SACCULES. 195 
 
 above described rods, contain a perfectly clear protoplasm, or are filled 
 with a uniformly granular substance, in which one can sometimes dis- 
 tinguish a nucleus. 
 
 With these Gregarines are associated, as Leydig 1 first showed, the 
 so-called "Psorosperm-saccules," discovered by J. Mliller. 2 These are 
 parasitic organisms of varying shape, some microscopic, some several 
 millimetres across, found often abundantly in the most diverse situa- 
 tions on the bodies of fishes and frogs (e.g., on the skin, gills, and in the 
 muscles, kidneys, or urinary bladder). To the naked eye, they ap- 
 pear as small white points or sacs. Their close relationship with the 
 Gregarines is proved by the nature of the contents, which consist of 
 hard-shelled Psorospermise, exactly like the Pseudonavicellse. They 
 only differ from the latter in minor characters, as the presence of a 
 tail-like process of the shell, such as is also seen on the eggs of some 
 ectoparasitic Trematodes (p. 45). 
 
 Yet it seems hardly allowable to class these Psorosperm-saccules 3 
 along with the Gregarines. For not only have they no capsular wall, 
 like that surrounding the group of young Pseudonavicellse, but further, 
 the formation of the Psorosperms generally begins at a time when 
 the organisms have not yet attained their full size, and goes on 
 throughout the whole subsequent life. What takes place in the Gre- 
 garines in two successive stages, is in the Psorosperm-saccules distinct 
 neither as regards space nor time. 
 
 And, besides the fact that the formation of Psorosperms takes 
 place without previous encystation, it must also be noted that the 
 resulting organisms have not the nucleus and firm cuticle of the Gre- 
 garines. They appear as simple masses of protoplasm with scattered 
 fatty granules. Their power of motion is also more limited, and is in 
 some cases, especially in the later stages, hardly perceptible. They 
 manifest their activity generally only in protrusion and retraction of 
 a part of their body- substance. 
 
 The formation of Psorosperm-saccules is effected thus the original 
 uniformly granular substance gradually becomes a mass of distinctly 
 defined balls (Fig. 98), which become surrounded with a transparent 
 covering, and then become single or double Psorosperms. These pass 
 away almost as soon as they are formed, and appear in all cases to 
 have a further development, so that their contents have usually a dif- 
 ferent character from that of the ordinary Pseudonavicellse. In some 
 
 1 " Ueber Psorospermien und Gregarinen," Mutter's Archiv f. Anat. u. Physiol., 
 p. 221, 1851. 
 
 2 " Ueber eine eigenthumliche krankhafte parasitische Bildung mit specifisch organ - 
 isirten Samenkbrperchen (Psorospermia)," ibid., p. 477 et seq., 1841. 
 
 3 Our knowledge of the Psorosperm-saccules rests specially on the researches of 
 Lieberkuhn, Mutter's Archiv f. Anat. u. Physiol., pp. 1-24 and 349-368, 1854. 
 
196 
 
 SPOROZOA. 
 
 cases indeed, as Lieberkiihn observed in those inhabiting the kidneys 
 of the frog, the contents fall into rod-like transparent bodies exactly 
 like the Pseudonavicellse of the earth-worm Gregarine. Here also 
 three to five of these rods usually have a granular ball lying between 
 them, and in one case Lieberkiihn saw these rods in distinct motion. 
 They not only glided slowly up and down the wall of the Psoro- 
 sperm, twisting and bending to suit the form of the interior space and 
 forcing the granular mass now here now there ; they also swelled up 
 into a globular form so as almost to fill the whole shell. The latter 
 suddenly burst, and the contents thus escaped, first the granular ball, 
 then the transparent rods, the latter also in spherical form and ex- 
 hibiting amoeboid movements for a short time. The empty shells 
 were very commonly found, and in the kidneys of the infected frogs 
 numerous amoeboid bodies were to be seen, some of which were 
 quite identical with the free creeping trans- 
 parent balls, while others enclosed finer and 
 coarser granular contents, and passed through all 
 the intermediate stages, leading finally to Gre- 
 garine parasites. All this led Lieberkiihn to con- 
 clude that the young brood grew to maturity 
 within the original host. 
 
 It is, however, still doubtful how far the 
 occurrence of these hyaline rods is constant 
 among the Psorospenns. In the majority of cases, 
 and in the common Psorosperms of fish, the 
 interior of the shell is filled with a clear homo- 
 geneous mass, near which, however, there are 
 two elliptical so-called " polar bodies " at one end 
 (Fig. 99,^4). One might perhaps suppose that these 
 are contracted rods, but according to the obser- 
 vations of Balbiani 1 and Schneider, 2 they appear 
 ^v 6810168 enclosing an exceedingly long and 
 bladder of the pike (after fine thread. This is usually twisted in a close 
 Lieberkuhn). spiral, but in some cases stretches out of 
 
 the shell through a special opening. The meaning of this thread is 
 not known, but this is at least certain, that Balbiani's idea of regard- 
 ing it as a sperm-cilium has no foundation. It is perhaps to be re- 
 garded as an apparatus of fixation. The possibility of regarding these 
 polar bodies as equivalents of the rods, is finally excluded by the fact 
 that the hyaline contents of the Psorosperms finally contract into a 
 spherical mass, which creeps out (when the shell is split in two by 
 
 1 Comptes rendus, t. Ivii., p. 157, 1863. 
 
 2 Arcfiir. d. zool. expfr., t. iv.. p. 548, 1875. 
 
EGG-SHAPED PSOBOSPEEMS. 
 
 197 
 
 pressure) as a mobile amoeboid organism (Fig. 99, B), as has been re- 
 peatedly observed both by Lieberkuhn and Balbiani. Since Lieber- 
 kiihn found these empty shells not unfrequently even within the 
 Psorosperm-saccules, and further saw the latter penetrated and sur- 
 rounded by amoeboid bodies, which agreed perfectly with the hyaline 
 balls previously liberated outside, it is probable that the young 
 parasitic brood sometimes escapes even within the host. 
 
 A third group of Sporozoa consists of the so-called " egg-shaped 
 Psorosperms," which are of special interest to us, since they occur as 
 parasites, and, under certain circumstances, as dangerous parasites, in 
 Mammalia, and even in man. They are not, 
 however, by any means confined to the higher 
 animals, for many species are found in Inverte- 
 brata, e.g., in the common garden snail, in which 
 a form of this kind was discovered more than 
 twenty years ago by Dr. Kloss in Frankfort, 
 
 and accurately followed through all its stages. x Gudus lota ; JB, from the gills 
 The term "Psorospermise," given to these para- with the ameboid 
 
 sites, is of course only slightly suitable, for the ^s out (*&*** Lieberkuhn). 
 body thus denoted is not comparable to a germ or spore, but represents 
 the Gregarinoid mother-animal, inside which the true Psorosperms are 
 
 FIG. 100. Coccidia from the intestine of the domestic mouse. A, inside an epith- 
 elial cell, still without a capsule ; B, C, encapsuled with Psorosperm and germ ; D, E, F, 
 isolated Psorosperms ; G, amoeboid brood (after Eimer). 
 
 afterwards developed. The only thing which recalls the Psorosperms 
 is the firm shell, with which these surround themselves at the close 
 of their period of growth, a structure evidently analogous to the cap- 
 sule of the quiescent Gregarine, which establishes here also the exis- 
 tence of an encapsuled resting-stage. In this state the parasites so 
 closely resemble the eggs of certain intestinal worms, that they have 
 often been mistaken for them even by experienced microscopists ; 
 
 1 "Ueber Parasiten in der Niere von Helix," Abhandl. d. Senkenberg. naturf. Ges- 
 , Bd. i., p. 189 ct seq., 1855. 
 
198 
 
 SPOROZOA. 
 
 and, vice versa, true worms have sometimes (by Eobin) been regarded 
 as Psorosperms. 
 
 FIG. 101. Coccidia from the kidneys of the garden snail A, inside a cell, still with- 
 out a capsule ; , C, encapsuled with Psorosperms inside ; D and E, Psorosperms with 
 germs, in E, in the act of exit (after Kloss). 
 
 So long as these creatures are destitute of a capsule, they appear 
 as membraneless cells with a distinct nucleus. In this stage, they 
 are usually found inside cells, especially epithelial cells, which they 
 gradually cause to swell up in consequence of their growth, and fin- 
 ally destroy by their exit, which usually occurs after the encystation. 
 The spores are formed from the granular contents of the Coccidium, 
 for by this name we shall henceforth designate the so-called " egg- 
 shaped Psorosperms." They are sometimes few in number, but some- 
 times many, and they are occasionally very numerous. The former 
 case is described by Eimer 1 in the form observed by him in the 
 
 intestinal epithelium of the mouse 
 (Eimeria, Schn., Fig. 100). The 
 other case is exhibited by the 
 Coccidia of the Mollusca, e.y., Helix 
 (Klossia, Schn., Fig. 101), or, stiU 
 better, by those of the cuttle-fish 
 (Benedenia, Schn.), which are also 
 infested by these parasites. 2 In 
 Coccidium oviforme (Fig. 102), which 
 is of special interest to us, there are, 
 as far as my observations go, always 
 four spores, which are provided as usual with a comparatively thin 
 shell. They only develop after the Coccidia have left the body of the 
 
 1 ' ' Ueber die ei- oder kugelformigen sog. Psorospermien der Wirbelthiere : " Wlirz- 
 burg, 1870. 
 
 2 The cells grow before the formation of spores to a size of above 2 mm. See obser- 
 vations of Eberth, Zeitschr. f. wiss. Zool., Bd. xi., p. 397, 1862; and Aim<* Schneider, 
 Archiv. d. zool. exjrfr., t. iv., p. 40, 1875. 
 
 FIG. 102. Coccidium oviforme from 
 the liver of the rabbit. In there are 
 Psorosperms in the interior. 
 
FORMATION OF SPORES AND GERMS. 199 
 
 host, and have lived for sometimes weeks or months in the water, 
 while in ordinary cases they are formed soon after the encapsulation, 
 or at least while yet inside the host. The shape of spore, so charac- 
 teristic of the Gregarines and Psorosperm-saccules, is here replaced 
 by a simpler spherical or ovoid form. 
 
 Along with the spore-formation there occurs simultaneously the 
 development of the embryonic body, which appears throughout to be 
 in the form of a hyaline sickle-shaped rod. Adjoining these, the 
 usual granular body ("nucleus de reliquat") is present with equal 
 constancy. The number of rods varies, but is generally from six to 
 eight (Fig. 100, D-F '; Fig. 101, D, JE). Coccidium oviforme always 
 forms only a single rod, 1 which lies on the granular mass (Fig. 102, (7). 
 
 When these structures attain development in the body of their 
 host, then, according to Kloss and Eimer, one can observe a distinct 
 movement, which, under favourable circumstances, may be watched for 
 hours, and is associated with a manifold change of form (Fig. 100, 6r). 
 When they pass into the quiescent state they assume a more or less 
 compressed, sometimes almost spherical form, although they usually 
 retain a slightly curved shape. Kloss calls the movement " leech-like," 
 and sometimes compares it with the creeping motion of a sluggish 
 Euglena. 
 
 In this contracted state these rods are in size and appearance 
 so thoroughly identical with the scarcely nucleated youngest stage of 
 the parasites, that (considering the contemporaneous presence and 
 the different number of stages) one can hardly be mistaken in con- 
 necting the latter directly with the mobile germs, and crediting 
 the forms in question with continuous multiplication. 
 
 Of course this applies only to what may be called the " viviparous " 
 species. When the formation of germs takes place outside the host, 
 as in Coccidium oviforme, then the appearance of immense numbers 
 must of course be due to often repeated introduction. 
 
 Whether structures somewhat similar to the above, the so-called 
 "Miescher's tubes" (Synchytrium Miescherianum^opf), are to be referred 
 to the class Sporozoa, is more doubtful, since no phenomena of move- 
 ment have yet been observed in any developmental stage. Since, 
 however, they are usually ranked with the Psorosperm-saccules, in 
 accordance with a decision which I was the first to give, 2 and have 
 indeed many points of resemblance with these forms, a brief discussion 
 of their nature is necessary. We must confess that our knowledge of 
 
 1 [Balbiani (loc. cit., p. 105) believes that he has proved that the sickle-shaped bodies 
 are double also in Coccidium oviforme, but that the two portions lie closely pressed to- 
 gether. R. L.] 
 
 - This work, first German ed., Bd. i., p. 240. 
 
200 
 
 SPOROZOA. 
 
 them is still very far from satisfactory or complete, although they 
 are of most common occurrence in our domestic animals, pig, ox, 
 sheep, and even deer. 
 
 The first to notice these curious forms was Miescher, who observed 
 the muscles of a domestic mouse penetrated in the direction of the 
 fibres by long strips, visible even to the naked eye, which on closer 
 examination appeared as cylindrical tubes filled with countless minute 
 kidney-shaped bodies. 1 Similar though shorter tubes were seen by 
 Hessling in the muscles of the roe and other Mammalia, and indeed 
 inside the muscular fibres, 2 still surrounded on all sides by the striated 
 sarcous substance. The observations of Eainey, who thought he had 
 in the tubes the first stage of the common bladder- worm of the pig, 3 
 and subsequent observations of my own, 4 proved that this occurrence 
 inside the muscular fibre was constant (Figs. 103 and 104). They 
 have not as yet been found anywhere else, although numerous observers 
 have in the meantime devoted close attention to them. 6 
 
 .. 
 
 
 FIG. 103. Rainey's tubes, enlarged about 
 40 diameters. 
 
 FIG. 104. One of Rainey's 
 bodies within an isolated muscu- 
 lar fibre, enlarged 100 diameters. 
 
 As long as the muscular fibres have their normal extension, the 
 tubes preserve an elongated form ; but this is altered, and gives place 
 
 1 Bericht iiber die Verhandl. d. naturforsch. Gesdlsch. zu Basel, p. 143, 1843. 
 Figured by v. Siebold, Zeitschr.f. wiss. ZooL, Bd. v., tab. x., Fig. 10, 11, 1854. 
 
 2 Zeitschr. f. wiss. Zool, Bd. v., p. 196 et seq., 1854. 
 
 3 Phil, trans., vol. cxlvii., p. 114 et seq., 1857. 
 
 * Loc. cit., where Rainey's mistake was corrected. 
 
 r> Of the numerous papers on these organisms, I may specially mention Manz, " Beitrag 
 zur Kenntniss der Miescher'schen Schlauche," Archiv }. mikrosL Anat., Bd. iii., p. 
 345 ct seq., 1867. 
 
DEVELOPMENT OF MIESCHER's TUBES. 201 
 
 to a more swollen shape, whenever the muscles are loosed from their 
 natural insertion and the fibres contract. 
 
 Their boundary wall consists of a somewhat thick and firm cuticle, 
 which (especially in younger, i.e., smaller tubes) is perforated by 
 numerous pore-canals, of course not always equally distinct (Fig. 105). 
 In consequence of certain external influences, the canals are often 
 united together by rupture, and in such cases the cuticle disintegrates 
 into a fringe of rods, as so often occurs also in the cuticular border of 
 the intestinal epithelial cells. Virchow regards these rods as parts 
 of the surrounding sarcous substance, 1 but in this he is mistaken, as 
 are also those investigators who (with Eainey and Eivolta) regard 
 them as cilia, and make them take part in the movement of the 
 organism. Inside the cuticle, embedded in a tough, somewhat homo- 
 geneous matrix, lie a countless number of microscopic (O'Ol mm.) 
 kidney-shaped or bean-shaped bodies. In their perfectly fresh state 
 these are of a hyaline appearance, containing at most a few sharply 
 defined granules near the ends, and forming- 
 after a while a few vacuoles. Independent 
 movements cannot be observed in those 
 bodies, although they exhibit manifold 
 changes of form. In the younger, i.e., 
 smaller, tubes (of only 07 to 1 mm.), we 
 find, beside and between the kidney-shaped 
 bodies, numerous round transparent balls, 
 
 probably to be regarded as the immature FIG. 105. Extremity of one 
 stages of the former. These structures are $* < ".*% 
 
 not equally Scattered throughout the pro- kidney-shaped bodies, much en- 
 
 toplasm of the tube, but are arranged in lar ecl 
 
 groups, enclosed in thin-skinned spheres of about 0-025 to 0'05 mm., 
 
 which lie together in a closely pressed mass (Fig. 105). 
 
 If, in determining the nature of these structures, we seek to 
 follow the analogy of the other Sporozoa, we may consider the balls 
 as spores, and compare the kidney-shaped bodies with the hyaline 
 rods. 2 The latter would therefore be the embryonic stage. Unfor- 
 tunately we cannot corroborate this plausible hypothesis by positive 
 experimental results. In an experiment which I made, a pig, 
 proved to be free from these tubes, was fed with them, and was 
 afterwards found to be infested with them. But on this I could lay 
 no special emphasis, not only because it was only a single case, but 
 
 1 " Lehre von den Trichinen," p. 23, 1866. 
 
 2 The occasionally slender form of these bodies indeed . recalls the rod-like or sickle- 
 shaped reproductive bodies of other Sporozoa. On the other hand, there are also Fungus- 
 spores of very similar shape. 
 
202 COCCIDIUM. 
 
 because the infection might have taken place in some other way. 
 Manz asserted his conviction that the digestive juice had a destructive 
 effect on the tubes ; and having used some for feeding an animal, he 
 could find, after a few hours, only their remains in the gastric con- 
 tents ; nor was there a trace of them in the intestinal wall or in the 
 muscles. 
 
 Although the tubes occasionally occur in immense numbers close 
 to one another, so that the flesh looks as if half of it consisted of 
 Psorospenu-tubes, yet they seem usually to cause no special uneasi- 
 ness. In many cases, however, the phenomena of paraplegia, retarded 
 respiration, and even suffocation, are observed as associated with the 
 presence of the tubes, and may with some probability be referred to 
 this cause (Damann, Leisering, v. Niederhausern). 
 
 These parasites have, however, no bearing on human pathology, 
 for in spite of their frequency and wide distribution (not even the 
 common fowl being exempt), they have never as yet been found in 
 man. Even the eating of flesh containing Psorosperms in abundance 
 has hitherto always proved harmless. 
 
 Having become somewhat familiar, through the foregoing informa- 
 tion, with the general structure and life-history of the parasites be- 
 longing to the Sporozoa, it is time to become acquainted more in detail 
 with the occurrence of these creatures in man. We shall therefore 
 turn to the consideration of the so-called " egg-shaped Psoroperm," of 
 which mention has already been made. 
 
 COCCIDIITM, Leuckart. 
 
 Kloss, "Ueber Parasiten in der Niere von Helix," Abhandl. d. Senkcnb. Geselhch. 
 Frank/., 1855. 
 
 Eimer, " Ueber die ei- oder kugelformigen sog. Psorospermien der Wirbelthiere." 
 Wuiv,burg, 1870. 
 
 Aime" Schneider, "Note sur la psorospermie du poulpe," Archiv. d. zod. exptr., t. iv. f p. 
 xl., 1875. 
 
 In, their youth, these parasites are naked inhabitants of epithelial 
 cells, but afterwards envelop themselves with a firm shell at the close of 
 their period of growth. In this condition, in which they present a 
 puzzling resemblance to the eggs of certain Entozoa, they quit their former 
 resting-place, and generally the former host also, and transform their 
 substance into a larger or smaller number of spores, each having a granular 
 ball and rod vrithin. The spores themselves have a rather thin wall, and 
 are of a round 01* elliptical shape. 
 
 We have already observed that the Coccidia occur preferably in 
 warm-blooded organisms, and that they sometimes appear in such 
 
COCCIDIUM OVIFORME IN THE LIVER. 203 
 
 enormous numbers, especially in the intestine and in the bile-ducts, 
 as extensively to destroy the epithelial cells, and produce pathological 
 changes of a very remarkable nature. Of all this family, Coccidium 
 oviforme, which we are about to describe, has been longest known 
 and most frequently observed, and is also the only one which has 
 hitherto been observed in man. 
 
 COCCIDIUM OVIFORME, Leuckart. 
 
 Kauffmann, " Analecta ad tuberculorum et entozoorum cognitionem," Dissert, inaug., 
 Berolini, 1857. 
 
 Lieberkuhn, " Ueber die Psorospermien," Mutter's Archivf. Anat. u. Phys., p. 7, 1854. 
 
 Idem, "Evolution des Gregarines," Mem. couronn. de VAcad. de Beige, loc. cit., pp. 
 26-34, 1855. 
 
 Stieda, "Ueber die Psorospermien der Kaninchenleber und ihreEntwicklung," Archiv 
 f. pathol Anat., Bd. xxxii., p. 132, 1865. 
 
 Keincke, "Nonnulla quaedam de psorospermiis cuniculi," Dissert, inaug., Berolini, 
 1866. 
 
 Waldenbure, " Zur Entwicklungsgeschichte der Psorospermien," Archivf. pathol. 
 Anat., Bd. xl.,"p. 435, 1867. 
 
 Kivolta, " Psorospermi e psorospermosi," Medico Veterinario Torino, t. iv., No. 2, 
 1869. 
 
 Idem, " Dei parassiti vegetali," p. 381 et seq.: Torino, 1873. 
 
 Egg-shaped bodies, 0'033 to 0'037 mm. long and 0'015 to 0'02 mm. 
 broad, with thick smooth shells, which have a micropylar opening at one 
 end, usually the narrower. The granular contents are sometimes uni- 
 formly distributed throughout the whole interior space, or sometimes, as 
 in the more globose forms, collected into a spherical mass (0*017 mm). 
 In this state the parasites pass from the liver and intestine ivhich they 
 inhabit to the exterior, there to undergo a further development in the 
 moist surroundings. The contents thereupon segregate into four oval 
 spores (0'012 mm. long, O'OOT mm. broad), which become surrounded with 
 a but slightly firm coat, and form each a single Q-shaped curved hyaline 
 rod, the concavity of which is occupied by closely packed granules. 
 
 The liver of the rabbit (Fig. 107) is not unfrequently found pene- 
 trated with white nodules, which, in more or less considerable num- 
 bers, grow gradually to the size of a hazel-nut, and excite painful 
 affections, in the course of which the animal often dies. In many 
 warrens the disease becomes a serious epidemic, so that hardly a 
 single healthy animal is to be found. On section of the nodules a 
 cheesy or purulent, sometimes yellow-coloured, mass exudes, in 
 which a microscopic examination reveals, besides cell debris, a count- 
 less number of the above-described oval bodies. Since the same struc- 
 tures are also found at the same time in the gall-bladder, it may also 
 be concluded that the nodules are in association with the bile-duct. 
 
204 
 
 COCCIDIUM OVIFORME. 
 
 These nodules are so like pseudoplasmic deposits that we can 
 understand how the first observers regarded and described them as such. 
 
 FIG. 106. Coccidium oviforme, from the liver of the rabbit ( x 550). C-G, stage* 
 of spore-formation only observed in the free state. 
 
 (Jarswell considered them to be tubercles, and Hake, 1 who was the 
 first to examine them more minutely, regarded them as carcinomata. 
 They were thought to have arisen from degeneration of the bile-ducts, 
 and to enclose numerous pus-corpuscles of peculiar form. Nasse 2 
 contradicted Hake's conclusion, and thought that the " pus-corpuscles " 
 should be regarded as abnormally altered epithelium. He compares 
 them to cartilage-cells, and urged that " the epithelium of the bile-duct 
 of sheep is sometimes found ossified, namely, when the sheep are in- 
 fested with Distomum" 
 
 FIG. 107 Liver of a rabbit with (Tpm'di urn-nodules. 
 
 The true nature of these bodies long remained uncertain, although 
 Remak 3 pointed out the resemblance between these structures and the 
 Psorosperms just discovered by Job. Miiller, and asserted their close 
 
 1 "A treatise of varicose capillaries, as constituting the structure of carcinoma of the 
 hepatic ducts, with an account of a new form of pus globuli :" London, 1839. 
 
 2 " Ueber die eiformigen Zellen der tuberkelahnlichen Ablagerungen in den Gallen- 
 gangen der Kaninchen," MiiUers Archivf. Anat. u. Physld., p. 209 et seq., 1843. 
 
 3 ' Diagnostische und pathologische Untersuchungen, " p. 235 : Berlin, 1845. 
 
STRUCTURE OF THE COCCIDIA. 205 
 
 relationship. Kauffmann 1 corroborated this, and tried to prove 
 the biological independence of the cells by observing that the enclosed 
 granular masses, after being kept for a while in water, broke up 
 into four parts, and became new Psorosperm-like bodies. Arguments 
 have been constantly brought forward, down to our own day, in favour 
 of the theory that these bodies were pathologically altered cells, 2 
 and all the more so when it was established that they occurred by no 
 means exclusively in the rabbit's liver, but not unfrequently in other 
 animals and in other organs, especially in and upon the intestinal 
 epithelium. On the other hand, the Coccidia were often regarded as 
 eggs of Entozoa, such as Distomes, and particularly D. lanceolatum; 
 and, indeed, their resemblance to the latter is on superficial inspection 
 very striking, for the size and appearance of the shell are identical, 
 and the micropylar opening recalls the little lid on the Distome- 
 egg. More minute examination of fresh specimens will, however, at 
 once reveal tjie characteristic differences. 
 
 With our present knowledge the nature of the egg-like bodies is 
 no longer a doubtful matter. The changes which they undergo after 
 they leave the body of their host, and the development which takes 
 place within the epithelial cells only admit of one explanation, that, 
 namely, which regards them as Gregarinoid parasites. 3 
 
 Considering the importance of the intracellular occurrence of 
 Coccidium, we may perhaps note that it was Eemak who first estab- 
 lished it. The fact has been confirmed, but only for the intestinal Coc- 
 cidium, by Klebs 4 and others (Waldenburg, Eeincke, Neumann, Eimer). 
 For our knowledge of the spore-formation we are indebted to Kauff- 
 mann, who first observed it, and also especially to Stieda and Eeincke. 
 
 Structure and Development. 
 
 When one examines Coccidia fresh from the so-called " Psorosperm- 
 nodule," it is easy to distinguish (Fig. 106, A, B) two different forms. 
 
 1 Loc. cit., p. 17. 
 
 2 See among others long, Archiv f. pathol. Anat., Bd. xliv., p. 202, 1868, and Koloff, 
 ibid., Bd. xxxiii., p. 512. I must not conceal that I myself for a while supported 
 this erroneous opinion. It originated in the observation of a case in which a dog infected 
 with Trichina; showed an intestinal membrane much altered by Helminthiasis, and covered 
 throughout its whole extent with a thick layer of egg-shaped Psorospermice. See my work 
 on Trichina, first edition, p. 11, 1860. 
 
 3 Among the investigators who have specially studied the developmental history of 
 Coccidia, Stieda alone dissents. His opinion regarding the Psorospermice, and especially 
 those inhabiting the liver of the rabbit, is that they are "very early stages of as yet 
 unknown animal parasites." I will in this connection only note that Stieda has not seen 
 the occurrence and development of Psorospermice within cells. 
 
 4 " Psorospermien im Tnnern von thierischen Zellen," Archiv f. pathol. Anat., Bd. 
 xvi., p. 189, 1859. 
 
206 COCCIDIUM OVIFORME. 
 
 The one is more slender, and filled with uniformly diffused granular 
 contents ; the other is thicker and provided with a granular ball, which 
 has a diameter of 0*017 mm., and lies in the middle of the internal 
 space, leaving a great part of it free. The latter contains a clear 
 fluid, which is easily coloured by staining fluids, and acquires in time 
 a somewhat firm consistency. One can not unfrequently recognise in 
 the granular mass of the ball another clear sphere of varying size, 
 which one would at once consider as a nucleus if it were more sharply 
 defined and allowed itself to be stained. In point of fact, however, it 
 can hardly be otherwise described than as a drop-like aggregation of 
 the clear ground substance which connects the granules together. I 
 have never been able to find a genuine nucleus. 
 
 The appearance of the contents exhibits many other differences in 
 detail. In the majority of Coccidia it is throughout of a finely granular 
 nature, but in other cases the protoplasm contains a more or less con- 
 siderable number of coarser granules, which are strongly refracting, 
 and not unfrequently flow together into larger masses like fat-granules. 
 Since Coccidia thus altered are much more common among forms which 
 have been cultivated than in fresh material, and since I have never 
 observed them to undergo any further change, I conclude that they are 
 dead specimens. The distinctively greater narrowing of one end is 
 hardly noticeable in the slender forms, and similarly the so-called micro- 
 pyle is for the most part, and that constantly, found in those of bulging 
 shape. Even the character of the shell varies, and is not unfrequently 
 double (Fig. 106, A), in the slender Coccidia. The outer wall is thinner 
 than the inner, which agrees exactly with the shell of the bulging forms, 
 both in its appearance and in its micropylar arrangement. Since there 
 are also specimens in which the outer shell is represented only by a 
 delicate more or less distant border, and others which are provided 
 only with a simple completely closed shell, this lends some support 
 to the opinion that the Coccidia in certain developmental stages cast 
 their skin, and afterwards assume the bulging form, with micropyle 
 and central mass of granules (Fig. 106, B). If we regard this shell 
 (which is provided with a micropyle, and perfectly resembles an egg- 
 shell in its refractive power and double contour) as a kind of capsule, 
 then the previous thinner coating may perhaps represent the true 
 cuticle. However, the fact that the capsule wall would then arise 
 under the cuticle, and not from it, as in the Gregarines, seems hardly 
 in favour of this opinion. 
 
 The formation of the body here described does not take place 
 freely in the interior of the enlarged bile-duct, but in its epithelial 
 lining. Although Stieda declared that he had never seen such a 
 mode of origin, and Waldenburg affirmed the same in regard to the 
 
STRUCTURE OF THE COCCIDIA. 207 
 
 Psorosperms from the liver, and although, on the other hand, others 
 (Vulpian, Koloff) have claimed the liver cells themselves as the germs 
 of the Coccidia, there can be no doubt of the above fact. Every well 
 prepared cross section furnishes convincing proof 1 (Fig. 109). 
 
 The wall of the Coccidium-nodulQS consists of a thick firm mass of 
 connective tissue with frequent nuclei and fibres, usually arranged 
 concentrically. Besides numerous blood-vessels, one can not unfre- 
 quently recognise, especially towards the periphery, smaller and larger 
 groups of liver-cells and of bile-ducts, which, although enlarged in 
 varying degrees, may be only slightly changed and often still contain 
 a regular columnar epithelium. 
 
 We might perhaps explain these appearances by supposing that 
 the connective tissue wall increases continually in thickness at the 
 expense of the liver substance, while the adjacent acini proliferate and 
 are crowded together in an ever widening circle. 2 
 
 This proliferation of the connective tissue takes place not only 
 outside the nodules, but extends also along the duct into the remoter 
 recesses. Where the acini are usually found crowded in close layers, 
 one finds in the diseased liver numerous bands of connective tissue of 
 varying thickness, which are embedded between the lobules. These 
 enclose a number of bile capillaries, which are often separated from 
 one another only by thin septa, but here and there include little areas 
 of the liver substance between them. These are essentially the same 
 changes as are observed in cases of severe hepatic cirrhosis, except 
 that in the latter the degeneration is restricted to this stage of develop- 
 ment, while here it goes further, inasmuch as at certain points where 
 the Coccidia have nested the bile-ducts widen and thus occasion 
 the formation of new nodules. Thus also it happens that the cysts 
 are often associated together, and can sometimes be extracted from 
 the liver as a root-like branched system of varicose cords. 
 
 At first sight these Coccidiicm-nodul.es may be seen to be utterly 
 different from the bile-ducts, even from those which were enclosed in 
 the bands of connective tissue. They have not only a wide saccular 
 
 1 I can only explain the opposite opinions by the supposition that the investigators 
 have neglected to make sections of sufficient fineness. 
 
 2 Thus we understand the repeatedly expressed opinion that it is the acini which 
 represent the proper source of the disease. Thus Koloff (Archiv f. pathol. Anat., Bd. 
 xliii., p. 522) states that the nodules arise by exuberant growth of the connective tissue 
 in and between the liver lobules, and that they change into Coccidia internally. Lang 
 (ibid., Bd. xliv., p. 202) refers the commencement of the disease to the liver lobules, and 
 describes it as a proliferation of cells, which takes place around the interlobular vessel, 
 and gives rise at once to the destruction of the glandular tissue and the formation of a 
 fibrillar connective tissue, which afterwards undergoes a retrograde metamorphosis from 
 the centre outwards, and thus produces the Coccidia partly from the alteration of the 
 cells grouped together in nests resembling cords. 
 
208 COCCIDIUM OVIFORME. 
 
 cavity, with the above-described caseous or cream-like contents, but 
 they have further no columnar epithelium. This has been replaced 
 by more or fewer round cells, which lie in a thick layer on the con- 
 nective tissue sheath, and resemble round granules in appearance 
 (Figs. 108 and 109). This is especially true of the larger cells, which 
 measure - 03 mm. and more in diameter, and not unfrequently project 
 more or less above their surroundings. 
 
 Another difference consists in the fact that the connective tissue 
 clothed with these cells is not only pushed out into numerous recesses, 
 but is also raised into folds, which run longitudinally and often in- 
 trude far into the inner space. In some places it is so much occupied 
 by these inwardly projecting folds that there are left only one or 
 two usually peripheral lateral spaces (Fig. 108). 
 
 - 
 
 FIG. 108. Cross section of a Coccidium-nodule, slightly enlarged. The contents have 
 been for the most part washed out. 
 
 On cross section the folds are very like papilloinatous elevations, 
 especially when they are low and, as sometimes happens, forked like 
 a Y- It is thus not difficult to understand how they have been hitherto 
 very generally described as such. Many of them may indeed repre- 
 sent exuberant growths of this kind, but the majority are undoubt- 
 edly nothing but the remains of the septa that separated the bile- 
 ducts which were originally more numerous. It is a mistake to refer 
 the nodules to a single much-distended bile-duct for the nature of 
 their origin, as above described, and the character of the intermediate 
 stages, show them to be formed from several closely connected bile- 
 ducts, which, being similarly altered, may gradually coalesce through 
 the more or less perfect disappearance of the dividing walls ; and we 
 need not point out how the presence of the side-chambers, hitherto 
 almost entirely overlooked, thus finds its natural explanation. 
 
 The intermediate stages, to which we have just referred, furnish 
 
GEOWTH OF THE COCCIDIA. 209 
 
 us also with the most convincing evidence that the nodules, in spite 
 of their distention and the very different nature of their contents, 
 are identical with the former bile-ducts. One can see the original 
 columnar epithelium 1 of the latter slowly pass into the above-men- 
 tioned cell-masses, and in such a manner that the individual cells, 
 influenced by the pressure and growth of the included Coccidium- 
 germs, alter very considerably inform and size. Not only the super- 
 ficial, but also the deeper epithelial cells share in this change, and 
 the more so since an active cell-multiplication is very often pro- 
 
 FIG. 109. The epithelium of a Psorosperm-nodule, filled 
 with parasites. 
 
 gressing simultaneously. As a rule, however, one finds in the larger 
 Psorosperm-nodules considerable spaces with a but slightly altered 
 columnar epithelium (Fig. 109). In other places all likeness to the 
 earlier stage is lost. Here and there the cellular layer is wholly 
 destroyed, so that the connective tissue projects without covering, 
 though the cells are usually replaced by a more or less thick, shining, 
 structureless layer of considerable consistency, and probably of a 
 colloid nature, as Lang has already mentioned. 
 
 What I have observed as to the growth of the germs, and the 
 consequent changes of the cells, agrees in the main with the descrip- 
 tions given by previous observers of the intestinal epithelium cells 
 infected with Psorosperms. I must, however, note that the examina- 
 tion of the intestinal epithelium, as I know from experience, presents 
 less difficulty, and shows the true state of the case on the whole 
 more readily. 
 
 The most difficult point, of course, is the demonstration of the 
 newly arrived parasites. I can say nothing definite about them. 
 The smallest germs I was able to distinguish with certainty were 
 slightly granular roundish masses of protoplasm of about 0*009 to 
 O'Ol mm., containing a comparatively large and clear nucleus-like 
 
 1 According to Lang, these columnar cells have been formed anew in the proliferation 
 of the connective tissue, and have then further grouped themselves in tubular nests. 
 
 
 
210 COCCIDIUM OVIFORME. 
 
 spot (0'005 mm.), which enclosed nucleoli, and was easily distinguished 
 from the cell-contents, though destitute of a special membrane. The 
 form of the enclosing cells varied very markedly, the transverse 
 diameter having grown to double the former size. This change was, 
 of course, still more striking afterwards, for the germ inside continues 
 growing till it finally becomes a spherical ball of about O026 mm. In 
 this state the parasite has, apart from the absence of the cuticle, an un- 
 deniable resemblance to a Gregarine. Its protoplasm is granular, but 
 always allows the nucleus to be seen glimmering through as a clear 
 spot. It now fills the cell so completely that the latter is seen only 
 as a narrow limiting envelope. I have usually been able to find the 
 original nucleus only in the earlier stages of the parasites. 
 
 The number of germs which find their way in is usually so con- 
 siderable that the cells are generally wholly infected with parasites of 
 different sizes and stages. It is by no means always a single germ 
 which invades each cell, two are sometimes found together, and 
 occasionally the number is still larger. I have found cells in which I 
 could distinguish five or six granular masses of unequal size lying 
 together. 1 
 
 As soon as the granular masses have attained their maximum size, 
 the transformation into the true Coccidium-ioim begins. The ball, 
 which has still retained its round form, assumes a more oval shape, 
 and surrounds itself under the previous enve- 
 lope with a rapidly thickening shell. As long as 
 the cell-wall persists, the Coccidia lie in or on 
 the walls of the liver-nodules, but later, as we 
 have seen, they are found in the inner space, 
 embedded in a finely granular detritus, with 
 nuclei, remains of cells, and shed epithelial 
 elements. 
 
 FIG. no. Adult Coccidia "VVe have already described (p. 206) how 
 these Coccidia (Fig. 110) change during their 
 
 stay in the liver. We know that the definitive shell, with its micropyle 
 and double contour, subsequently appears under the original primordial 
 coat, 2 and that the granular protoplasm within rolls itself up into a ball 
 in the middle of the capsule. 
 
 1 Waldenburg and Rivolta account for several germs within one cell (seen also by 
 Klebs, Reincke, and Neumann), not by a repeated immigration, but by a division of the 
 original occupant. 
 
 2 I may here expressly note that this assertion rests on no confusion with the 
 remains of the cells which lie immediately round the Coccidia, for the casting of the skin 
 can sometimes still be observed in specimens which have been kept for some time in water. 
 On the other hand, the representations which Lieberkiihn makes of Coccidia with double 
 walls obviously refer (since sometimes two or three Coccidia are lying within the same 
 envelope) to specimens still within their epithelial cells ("Evolution des Grdgarines," 
 loc. cit., p. 33). 
 
GROWTH OF THE COCCIDIA. 211 
 
 I have never been able to observe any further change in the 
 Coccidia within their host. A like want of success has attended most 
 of the earlier observers of Coccidia in warm-blooded animals, and that 
 whether the germs originated in the liver or in the intestine. The 
 only one who reports differently is Eimer; but the object on which 
 he bases his results is plainly different from Coccidium oviforme, and 
 cannot be directly ranked with it, as we shall afterwards see. 
 
 But the Coccidia do not remain permanently in their hosts. They 
 pass, though indeed only to a small extent, through the communica- 
 tions which persist here and there between the nodules and the bile- 
 ducts, and reach sooner or later the gall-bladder and intestine, 
 and are finally expelled with the fseces, just as are the parasites 
 and eggs directly developed in the intestine. Having reached the 
 exterior, they undergo, like the eggs of worms (p. 54), a further de- 
 velopment, after a longer or shorter period of incubation. This was first 
 discovered by Kauffmann (1847), and since then closely studied, espe- 
 cially by Lieberkuhn, Stieda, Reincke, and Waldenburg. 1 The results 
 of the last two investigators (except the later experiments of Walden- 
 burg) apply not to the so-called hepatic Psorosperms, but to the 
 Coccidia of intestinal epithelium ; but these, unlike Eimer's specimens, 
 are forms which exactly coincide with Coccidium oviforme in all 
 essentials, if they be indeed a distinct species. 
 
 The length of the period of incubation varies in individual cases. 
 Kauffmann observed Coccidia kept in water develop after fourteen 
 days, Stieda only after six weeks, and Leiberkiihn after months, while 
 "Waldenburg and Eeincke found Coccidia forming spores after a lapse 
 of four to five days, or less. My own cultivation-experiments, which 
 began early in February, furnished, in about a month (in a warm room), 
 the first specimens with Psorosperms. At first there were only a few, 
 but they increased in the course of the following weeks, and towards 
 the end of March the majority of the Coccidia had undergone their 
 metamorphosis. The others, which were mostly young forms, with 
 their protoplasm still diffuse, seemed to be dead. But all this was in 
 only one of my cultivations. In other bottles, which stood in a cooler 
 place, only a few specimens attained further development even after 
 nine weeks, although they still seemed, with few exceptions, quite 
 healthy. 
 
 Like the hard-shelled worm-eggs, the Coccidia have very con- 
 siderable power of resistance, so that neither chromic acid nor 
 chromate of potassium, of ordinary strength, seem to have an in- 
 
 1 Even in 1862 Waldenburg abandoned his early, undoubtedly somewhat imperfect, 
 observations. See his paper, " Ueber Strucktur und Ursprung der wurmhaltigen 
 Cysten," Archiv f. pathol. Anat., Bd. xxiv., p. 149, 1862. 
 
212 COCCIDIUM OVIFORME. 
 
 jurious effect on them. Indeed, it has been stated that their de- 
 velopment proceeds more rapidly in these solutions than in water, 
 but this certainly seems to me to require further corroboration. 
 
 Whether it be by chance or not, the shortest period of incubation 
 has been as yet exclusively observed in intestinal Coccidia. Walden- 
 burg, in the later experiments which he made with hepatic Coccidia, 
 was, like the others, unable to observe further development till after 
 the lapse of weeks or months. He thinks it possible that the chromic 
 solution with which he treated his objects might possibly penetrate 
 the intestinal walls more easily and more thoroughly than the masses 
 of liver; but the insufficiency of this explanation was shown by the 
 fact that isolated hepatic Coccidia, though far more accessible to ex- 
 ternal influences than the Coccidia of the intestinal epithelium or 
 Lieberkiihnian glands, yet required hardly any shorter time for their 
 development. 
 
 The changes which occur in the free-living Coccidia (Fig. Ill) are 
 concerned, as we have previously noted, with the production of spores 
 the only structures which we can compare with the Psorosperms of 
 allied organisms, and which we might designate by the same name 
 if we wished to use the word in connection with Coccidia. Kauff- 
 mann declares that these Psorosperms agree with the parent Coccidia 
 in everything but size ; but Lieberkiihn has already justly condemned 
 this statement. The Psorosperms are not only much smaller (0'012 
 mm.) than the Coccidia, but are in their organization hardly less 
 divergent than is the case in the other Sporozoa. The insufficient 
 microscopic power used must certainly be to blame for Kauffmann's 
 mistake. 
 
 He has, on the other hand, observed with perfect accuracy that 
 the spores originate by division of the central granular mass. It only 
 rarely happens, indeed, that the actual division x is seen, but that only 
 proves that it takes place with great rapidity. In the cases I have 
 observed the four parts can always be distinguished 2 in the granular 
 ball, even when this is still a coherent mass ; so that I must leave it 
 undetermined whether a division into two first occurs, or whether the 
 four spheres are present from the beginning. Along with the granular 
 mass the clear plasma inside also divides, so that at the close of the 
 process four segmentations-pheres are found inside the shell, which 
 differ (Fig. Ill) from the former central mass in their smaller size 
 (0-009 to 0-01 mm.). 
 
 1 Waldenburg says he has sometimes observed this segmentation while the Psoro- 
 spermice were yet in the liver. 
 
 2 I have always found four segmentation spheres and four Psorosperms, never more 
 nor less, although many observers report two or three. Cases of an apparently smaller num- 
 ber are always optical illusions, in which two Psorosperms lie upon and obscure one another. 
 
INCUBATION GROWTH OF THE SPORES. 
 
 213 
 
 FIG. 111. Development of 
 
 But these segmentation-spheres very soon assume another shape, 
 changing from a spheroidal to an ovoid form, and pressing to the 
 side the clear plasma which was formerly 
 wholly surrounded by the granular mass, and 
 which had also been increasing at the expense 
 of the latter. The substance of the segmenta- 
 tion-spheres undergoes a further differentia- 
 tion, and produces finally a transparent curved 
 C-shaped rod. A thin, but tolerably firm, sur- 
 rounding envelope is at the same time secreted. 
 The rod lies with its convex surface on this 
 above-mentioned envelope, while its concavity Psorosperms in Coctidia. 
 embraces the remainder of the granular mass, drawn together into a 
 minute ball (O005 to O'OOG mm.), and presenting the appearance of 
 an embryo and its yolk-sac (Fig. 112). I have no scruple in regarding 
 the latter as the so-called " nucleus de reliquat," and the rod as the 
 proper reproductive body. 
 
 The description which Stieda gives of these Psorosperms is in 
 perfect harmony with my observations. I must specially note my 
 agreement with him on this point, that the rod consists of a uniform, 
 perfectly hyaline substance, and is swollen at its ends into a strongly 
 refracting ball, which perceptibly exceeds the diameter (O003 mm.) 
 of the connecting part. When this connecting part lies in the direc- 
 tion of the optical axis, as not unfrequently happens, one sees only 
 the two terminal knobs of the rod, which, with the intermediate 
 granular ball, form the figure described by Lieberklihn, 1 according to 
 whom the contents of the Psorospermice consisted of two transparent 
 polar bodies, separated by a granular ball. This view is of course 
 dissipated when the object is seen from the side. 
 
 The newly formed rods (Fig. 112, B) have by no means that 
 strong refractive power which they afterwards acquire. Even 
 the little heads are still feebly lustrous, and present essentially 
 the same appearance as the plasma enclosed in the former segmen- 
 tation-spheres. 
 
 The representation which Reincke gives of the rods differs in so 
 far as he denies their homogeneous nature, and describes three or four 
 " globuli coerulei in modum cerse lucentes," lying behind one another, 
 which are sometimes so large that they fill up the whole diameter. 
 Two of these structures represent the heads of the rods ; the others 
 the thinner median portion. 
 
 I have seen forms which bore out the above description, in so 
 far as the heads sometimes seemed as if disjointed, and the median 
 
 1 MiiUcr's Archivf. Anat. . Physiol, p. 8, tab. ii., Fig. 37, 1864. 
 
214 
 
 COCCIUIUM OVIFORME. 
 
 part displayed two segments lying one behind the other, although all 
 the parts were meanwhile still joined together by a slightly refractive 
 connective substance. I do not, however, believe that these objects 
 represent the normal state, not only because they only appeared in 
 my infusion when the number of Coccidia containing Psorosperms had 
 increased, but also because they are the prelude to an almost visible 
 destruction of the germs, the details of which will be afterwards 
 summarised. 
 
 FIG. 112. Coccidia enclosing Psorosperms. 
 
 Nor can I agree with Eeincke in saying that the Psorosperms are 
 without an envelope, and that it is only the boundary of the rods 
 which sometimes presents this appearance. If Keincke had ever 
 made the experiment of bursting the shells of Coccidia, and press- 
 ing out the Psorosperms, he would have had no further doubt as 
 to the existence of the envelope. It is, as we have said, a thin but 
 sharply defined and tolerably firm membrane, bearing a little knob, as 
 Stieda mentions, at its sharper extremity. 
 
 The clear substance still contained in the interior of the Coccidia. 
 seems to be of a somewhat consistent nature, as may be concluded 
 from the fact that the Psorosperms only rarely change their position 
 under pressure of the cover-glass. One can sometimes further observe 
 (Fig. 112, D) a sharply denned line running down the middle from the 
 micropyle, which looks just like a fold or narrow canal, which is 
 hardly possible in such a fluid plasma. 
 
 At this stage the development of the Coccidia is for the meantime, 
 in my opinion, complete. Like the eggs of Entozoa containing em- 
 bryos, they await an opportunity to gain access into a new host, and 
 this opportunity can hardly fail, for the Coccidia brought to the 
 exterior with the faeces undergo exactly the same changes in the 
 rabbit warren as in our glass vessels, and will therefore rapidly 
 populate these places with countless germs. 
 
 Unfortunately I have not yet had opportunity of proving the 
 possibility of infection by these Coccidia and their Psorospermice, and 
 thus of establishing a supposition, which is rendered highly probable by 
 
WALDENBURG'S OBSERVATIONS. 215 
 
 all that we know of the reproductive processes of related organisms. 
 This blank has, however, been filled up by other experiments con- 
 ducted by Waldenburg 1 and Eivolta, 2 who, by feeding with Coccidia 
 containing Psorospermice, produced new Coccidia. Eivolta expressly 
 remarks that the presence of the Psorospermice is an essential con- 
 dition of success, since Coccidia with unsegmented contents remained' 
 without change in the alimentary canal of the animal experimented 
 upon. Since Eivolta experimented on fowls, and since the Coccidia of 
 these animals represent a distinct species, let us restrict ourselves first 
 to an experiment of Waldenburg's, made on a rabbit four weeks old, 
 and of healthy stock. 
 
 Use was made of intestinal Coccidia 3 with their contents divided 
 into four, and still in their original place of formation that is, in the 
 harbouring organs. On the fourth day after feeding there were found 
 on the surface of the intestinal mucous membrane not only a few 
 small mature "Psorospermice" (i.e., Coccidia), but also "numerous round 
 distinctly nucleated bodies, with a fine, often indistinct, membrane, 
 and granular contents lying closely upon it," bodies in fact perfectly 
 resembling the young Coccidia, usually found enclosed in the epi- 
 thelial cells. Control observations made on other rabbits born and 
 bred with the one experimented on gave a negative result. As to 
 finding the parasites free on the mucous membrane of the infected 
 animal, Waldenburg concludes that immigration " into the epithelial 
 cells is by no means necessary for the development of the Psoro- 
 spermice, especially since in other cases one only finds a comparatively 
 small number shut up in the cells." 
 
 Against this statement a subsequent conclusion of Waldenburg's 
 must be placed, although he still upholds the cogency of his feeding- 
 experiment. By cultivation of livQT-Coccidia, he was convinced that 
 the series of changes undergone by the parasite in its free life is by 
 no means terminated by the formation of the spores above described. 
 He denies that the four enclosed bodies are Psorospermice. They are 
 considered as segmentation-spheres, which, beside and in addition to 
 the granular mass, enclose a clear nucleus at the poles. He contends 
 against calling these nuclei the ends of a distinct rod-like body, and 
 would indeed dispute the existence of any such thing. 
 
 After some time the number of these nuclei doubles. Within the 
 membrane of the Coccidium there then appear segmentation-spheres, 
 
 1 Loc. cit., Bd. xxiv., p. 163. 
 
 " Parass. veget.," p. 390. 
 
 3 A careful examination of these fragments was not undertaken by Waldenburg, who 
 at that time was only acquainted with the investigations of Kauffmann. According to tho 
 figures, they are normally developed Psorosperms. 
 
216 COCCIDIUM OVIFOKMK. 
 
 with four nuclei arranged crosswise, and containing a granular mass, 
 which lies embedded between the nuclei, and gathers itself around 
 them. Finally, in the last stage of this developmental process Wal- 
 denburg observed that the individual segmentation-spheres had each 
 divided into four new spheres, which enclosed a clear nucleus, and 
 had quite the same appearance as the original spheres, though of 
 course smaller. Thus the Coccidia contained sixteen small indepen- 
 dent bodies, which had resulted from a repetition of the division of 
 the original contents into four. 
 
 In these bodies Waldenburg thinks he has at last found the 
 true germs of the Coccidia. They still partially cohere in fours, 
 and issuing from the micropyle, or from an accidental breach, they 
 exactly resemble in action and appearance certain bodies which 
 originate in great number in the liver-cysts, and which he regards 
 as the youngest stage of the Coccidia. The bodies under dis- 
 cussion are described as about the size of a red blood corpuscle, some- 
 times larger or smaller, some spherical, others oval, some elliptical, 
 others sickle-shaped, and occasionally even provided with fine pro- 
 cesses. A distinct membrane is not visible, but a nucleus is usually 
 quite distinct. Waldenburg believed he could observe an "apparently" 
 active, " at any rate not wholly " passive movement, and felt warranted 
 in regarding them as amcjeboid organisms. 
 
 Nor is Waldenburg the only one who maintains the further de- 
 velopment of the four parts. Kivolta also reports similar processes, 
 but he supposes that the parts do not segment afresh, but gradually 
 form internally, at the expense of the granular mass, two, three, or 
 four shining bodies, which represent the germs (" micrococchi psoro- 
 spermici"). They possess great power of resistance to external in- 
 fluences, and can even survive desiccation. In the first reports (1869) 
 these germs, and even the segmentation spheres, were credited with 
 cilia, and regarded as Infusoria. 
 
 I cannot deny that really observed states lie at the foundation of 
 these representations ; nevertheless, I cannot regard the changes which 
 they exhibit as normal stages in the development of the parasites, but 
 consider them simply as the phenomena of a dissolution which takes 
 place in old infusions, as above indicated. The spores change their 
 earlier ovoid form for a rounder one, the rod inside becomes indistinct, 
 the shining heads become displaced and disjointed, or the whole rod 
 may fall into pieces, while the granular mass becomes inflated, and 
 the granules flow together into coarser grains ; a series of deceptive 
 appearances thus originating to which the influence of a fixed idea 
 easily lends an undue importance. 
 
 Even in Lieberkuhn's researches we find figures which exhibit such 
 
TRANSFERENCE OF THE SPORES. 217 
 
 abnormal states. This is true at least of the " transparent balls," of 
 varying number, which surround the contents or segmentation spheres, 1 
 which I know from my own experience to be referable only to changes 
 which have befallen the Coccidia in earlier stages before the formation 
 of the rod. 
 
 I have never been able to establish an independent exit of spores 
 or of rods. Sometimes, indeed, I found free spores in my infusions, 
 but so seldom, that I am inclined to think they had been liberated 
 by mechanical influences. It is perhaps, therefore, to be concluded 
 that the germs usually find entrance into the subsequent host while 
 still within the Coccidium-sholls. A transference in the free state, as 
 maintained by Waldenburg, is very improbable, since after their 
 arrival in the stomach they are for a time exposed to the influences 
 of the digestive juices, which they could hardly sufficiently resist 
 without a protective shell. 2 
 
 We may then conclude that it is in the stomach that the rod-like 
 germs first escape out of the shell by means of the special micropyle. 
 Then they probably draw themselves together into a ball, become 
 amoeboid, and reach the liver by the duct us choledochus. There 
 they bore into the epithelial cells, and become new Coccidia. The size 
 of the rods suggests no difficulty, for they measure, in spite of their 
 considerable length, hardly more than O006 mm. in diameter in their 
 contracted state; they are therefore very considerably smaller than 
 the smallest young forms I have seen (0'009 mm.). To follow out the 
 difference between them, we may note that besides growth a certain 
 differentiation of the protoplasm takes place, in consequence of which 
 the parasite loses its originally hyaline nature, and becomes a purely 
 granular nucleated mass. But these are changes which also occur 
 in other Sporozoa in a similar manner, and may therefore be ac- 
 cepted without scruple. A comparison with allied organisms also 
 corroborates the supposition that the granular mass shut in with the 
 rod in the spore-sac is of no importance in the further development. 
 
 It is further self-evident that the conclusions here stated all re- 
 quire further corroboration. *"0ur knowledge of the Coccidia can only 
 become satisfactory when the processes discussed are directly observed. 
 As long as this is wanting, we may, however, conjecture, and fill up the 
 blanks by deductions from analogy. One must only be able to show- 
 that the suggested processes do not in any way contradict real ob- 
 servations. 
 
 Perhaps it may appear as though I had not myself fulfilled this 
 condition, when I claim for the rods both contractility and mobility, 
 
 1 " Evolution des Grdgarines," loc. cit., pp. 8 and 9, Tab. ii., Figs. 35 and 36. 
 - See remarks on pp. 58 and 75. 
 
218 COCCIDIUM OVIFORME. 
 
 without having seen either. But the negative result is not decisive, 
 and the less so since the conditions in which we should expect to find 
 movement are not by any means identical with those which obtain 
 in our incubating apparatus and infusions. But there are many 
 parasites of whose vital energy and mobility we should form quite a 
 false impression if we confined ourselves solely to the observation of 
 the animal outside its host, especially if that host be a warm-blooded 
 animal. 
 
 In support of my opinions in regard to the reproduction and de- 
 velopment of Coccidium oviforme, I may finally refer to the observa- 
 tions which Eimer has made on the intestinal Coccidia of the mouse, l 
 a form which cannot, however, as it is by Eimer, be directly identified 
 with the hepatic Psorosperm. 
 
 In the intestine of the infected mice, which seemed almost synony- 
 mous with all the mice of that locality, Eimer found a great number of 
 small sickle-shaped curved creatures of from 0*01 to 0*016 mm. in size, 
 with a generally homogeneous shining appearance, and at most con- 
 taining extremely fine granules. In size, form, and structure they 
 were most undeniably like the transparent rods above described. 
 Sometimes these were surrounded by a spherical, delicate membrane 
 (O'Oll mm.), which (Fig. 113, D-F) enclosed six or eight in an often 
 regular arrangement ; but, as a rule, they were free and isolated, and 
 in continual motion. They bent stiffly together, and stretched them- 
 selves again, sometimes more quickly, sometimes after longer intervals, 
 and finally, they assumed under the eye of the observer, by contract- 
 ing and rolling up, the form of a clear homogeneous ball, about the 
 size of a white blood corpuscle, and exhibiting an amoeboid move- 
 ment (Fig. 113, G). Such balls were seen in hosts in the mucus, and 
 also inside the epithelial cells of the intestine. Besides these, still 
 larger cells were to be seen, with nucleus and finely granular contents. 
 They passed on the one side through a series of intermediate forms 
 into the homogeneous balls, and, on the other hand, they might be 
 traced through all the stages of development to the adult, round 
 (0*018 mm.) or ovoid (0*026 mm. long, 1)y 0*016 mm. broad) Psoro- 
 spermice. The latter contain sometimes scattered, sometimes aggregated 
 contents, as in Coccidium oviforme, and were, like them, provided with 
 a smooth, double contoured shell, sometimes with a recognisable micro- 
 pyle at each end. Eimer sees in these " Psorospermice " the encysted 
 stage of a Gregarinoid parasite, which he calls Crregarina, in reference 
 to the appearance of the young forms. 
 
 The dung of these mice contained, besides the usual forms of Psoro- 
 
 1 " Ueber die ei- oder kugelfonnigen sog. Psorospermien der Wirbelthiere :" Wiirz- 
 burg, 1870. 
 
INTESTINAL COCCIDIA OF THE MOUSE. 219. 
 
 sperm, others, in whose granular contents were embedded varying 
 numbers of clear shining bodies, of about the size of the smallest 
 amoeboid cells. These were found both in the cysts with diffuse 
 contents and in those in which the contents had been retracted from 
 the wall. 
 
 In a subsequent investigation similar stages were also found in the 
 intestine. And further, it was proved that the shining bodies not only 
 multiplied at the expense of the granular mass, but were also changed 
 into sickle-shaped Gregarines, which were surrounded by a membrane 
 originating in the outer surface of the granular ball (Fig. 113, B, C), 
 and which issued from the Psorosperm capsule in this envelope. 
 Already very decided movements could be observed in the young 
 Gregarines, which pushed against one another in the most varied way 
 within the common covering. Sometimes the movements of the 
 isolated animals were to be seen, as above described. They manifested 
 themselves sometimes as contractions, in consequence of which the 
 sickle-shaped structures became " apparently rod -like bodies with 
 terminal balls," and thus assumed a shape in which they perfectly 
 agreed with the rod-like germs of the common Coccidia. Between the 
 Gregarines there was often to be seen a spherical remnant of the 
 original granular mass inside the enveloping vesicle. 
 
 FIG. 113. Coccidia from the intestine of the domestic mouse. 
 A , Inside an epithelial cell, still without capsule ; B and C, Encapsuled 
 forms, with Psorosperms and germs ; D-P, Isolated Psorosperms ; G, 
 Amoeboid brood (after Eimer.) 
 
 There can be no doubt that the enveloping vesicle in the above 
 case is to be regarded as a real Psorosperm, which produces a con- 
 siderable number of rod-like or sickle-shaped germs, but itself origi- 
 nates singly within the " encapsuled Gregarine." Since the formation 
 of spores and germs takes place, as in the so-called Klossia and 
 Benedenia (p. 108), within tke body of the host, the whole develop- 
 ment of the parasite progresses in continuous succession, 1 and there 
 
 1 It is a striking fact that Eimer observed in Psorospermice preserved in chromic acid 
 solution not the above developmental process, but a peculiar segmentation of the granular 
 contents, in consequence of which three,, four, six, and probably even twelve granular balls 
 were fonned under the capsular membranes. Besides these, there also appeared on 
 several occasions, sickle -shaped, shining structures which agreed with the young Gre- 
 garines, except in the absence of vital phenomena (loc. cit., p. 15). 
 
220 COCCIDIUM OVIFOKMK. 
 
 thus result, in spite of all other analogies, such considerable differ- 
 ences between Eimeria and Coccidium oviforme that an identification of 
 the two seems quite impossible. 
 
 In view of this fact, the question presses, whether the Coccidia ob- 
 served in the intestine of other Mammalia the dog, cat, rabbit, and 
 man are not perhaps also different from Coccidium oviforme, found 
 in the liver of the rabbit ? Hitherto these organisms have been con- 
 sidered as quite identical or as but slightly different. They were all 
 nothing else than " oval or spherical Psorospermice" But that is of 
 course no reason for at once regarding them as specifically identical. 
 Even the common body-form and the similarity of the parasitism are 
 not enough ; the same might be said of Eimeria, but if Eimer's observa- 
 tions be correct, it is a separate form. It is true that such peculiari- 
 ties of reproduction and development as Eimer described in Eimeria 
 are not to be observed in the intestinal Coccidia of the other Mammals. 
 In fact, the latter agree closely, so far as we know, with Coccidium 
 oviforme, so that we have hitherto ranked them together without 
 scruple. 
 
 But none the less does the identification of intestinal and hepatic 
 Coccidia seem to me unwarranted, or even, to tell the truth, improbable. 
 
 I have previously noted the differences which obtain between 
 them in the duration of their period of incubation the former require 
 hardly as many days as the others weeks. The suggested explanation 
 of this difference has also been noticed, but this could hardly be a suffi- 
 cient explanation when the two forms were regarded as identical, while, 
 on the other hand, their divergent habit makes further discussion un- 
 necessary. It must also be remembered that the Coccidia in question 
 (both of course in their encysted stage) differ not inconsiderably in 
 size. While the hepatic Coccidia are described by all investigators as 
 bodies 0*015 mm. broad by 0*032 to 0*037 mm. long, the dimensions 
 of the intestinal Coccidia in the rabbit (according to Keincke and 
 Neumann, the only investigators who give measurements) are 0*024 
 mm. long by 0*0128 to 0*012 mm. broad. Thus the latter are very 
 decidedly smaller than the former. Finally and this fact is very im- 
 portant for the decision of the question there is no case known 1 in 
 which the two kinds of Coccidia have been found beside one another 
 in the same organism, 2 although that ou<jht surely to be very frequent, 
 if not constant, if the same germs were able to develop either in the 
 intestine or in the bile-ducts. 
 
 1 In the eases of intestinal Coccidia, mentioned by Reincke, Waldenburg, and Klebs, 
 the absence of hepatic Coccidia is expressly stated. 
 
 2 This does not in any way contradict the possibility of the two forms occurring in the 
 same organism, indeed this no doubt frequently occurs. 
 
PATHOLOGICAL SIGNIFICANCE. 221 
 
 I think we may therefore, in the meantime, conclude that the 
 intestinal Coccidia, which have been observed by Kjellberg 1 and 
 Eimer 2 even in man, constitute a species different from Cocddium 
 oviforme, characterised especially by their smaller size, their short 
 period of incubation, and their position in the epithelial cells of the 
 membrana villosa. Considering the changes in the epithelium 
 effected by this parasite, and first observed in this case, the species 
 may be not unfittingly named Cocddium perforans. 
 
 [That the intestinal Coccidia of Mammalia belong to numerous 
 different species may be seen not only from the forms observed by 
 Eimer, but also from the discovery of Cocddium Rivoltce, Grassi, 
 which inhabits the large intestine of the cat, and, after a period of 
 cultivation in water, produces two Psorosperms, each of which yields 
 four sickle-shaped bodies. 3 E. L.] 
 
 Pathological significance of Coccidia. 
 
 The foregoing account shows indubitably that the changes caused 
 by the Coccidia in the bile-ducts and liver are, or may be, of fatal 
 importance. They not only exert a pathological influence by inter- 
 fering with the normal function of the liver, by obstructing the 
 secretion of bile over a more or less considerable area, by destroying 
 the tissue of the gland, and thus restricting the quantity of secretion, 
 and by deteriorating the quality of the latter by mixture with other 
 substances, but also by pressing on the blood-vessels of the liver, and 
 causing more or less intense disturbances of the circulation according 
 to the position and size of the tumour. To what degree metabolism 
 may be affected in consequence may be illustrated by the fact that, 
 according to my honoured colleague Professor Cohnheim, it is im- 
 possible to produce diabetes by the usual operation in a rabbit in- 
 fested with Coccidia. As soon as the disease has attained a con- 
 siderable development, the animals die. They become very thin after 
 being sickly for some weeks, they lose their appetite and previous 
 activity, begin to breathe quickly and violently, and finally die in 
 convulsions. 
 
 Nor does the rabbit alone thus suffer, but even man, although he 
 is obviously not exposed in the same degree to the possibility of a 
 frequent and numerous introduction of germs, is occasionally affected ; 
 and the first case which has come within the range of observation, 
 
 1 Virchow's Archiv f. pathol. Anat., Bd. xviii., p. 527, I860. 
 
 2 Loc. cit., p. 16. 
 
 3 See Grassi, " Intorno ad alcuni protisti endoparassitici, " Atti Soc. Ital. Nat. Sci.: 
 Milano, vol. xxiv., 1881. 
 
222 COCCIDIUM OVIFORME. 
 
 described by Gubler in Paris, 1 furnishes us with a striking instance 
 of what, under some circumstances, may be the result of their presence. 
 
 The case was that of a stone-breaker, forty-five years of age, who 
 sought admission to the hospital, suffering from disordered digestion, 
 bad appetite, sour stomach, and anaemia. He felt a dull pain in the 
 right hypochondrium, associated with a cachectic appearance. Per- 
 cussion revealed a considerable enlargement of the liver, and palpation 
 disclosed a markedly projecting spherical tumour, lying about the 
 position of the gall-bladder. The diagnosis referred the disease to 
 Ecliinococcus. In the next few weeks the anaemia increased so much, 
 that finally the lips were no longer distinguishable in colour from the 
 rest of the face ; the patient then fell one day to the ground, after 
 which ague, and afterwards violent pains in the body, fever, feeble 
 pulse, vomiting of bile, and collapse followed. After a night of de- 
 lirium, death supervened. 
 
 A post mortem examination showed that the patient had died of 
 peritonitis. In the substance of the much enlarged liver there were 
 found about twenty tumours of cancerous appearance. Most of them 
 were about the size of a chestnut, some even as big as an egg, and the 
 one which had been seen from the outside was of enormous size, 
 12-15 cm. in diameter. Internally, the encapsuled tumours con- 
 tained a thick creamy fluid of a greyish-brown colour, here and there 
 somewhat reddish, in which there were, besides numerous altered 
 epithelial cells and blood corpuscles, countless egg-like bodies, which, 
 according to the figure and description, possessed all the characteristics 
 of Coccidia. At the sharper end of the shell, Gubler saw a small flat- 
 tening " like a lid or micropyle." In many cases the granular con- 
 tents were rolled together into a ball. The wall of the tumour was 
 strongly injected, and was at one point also ulcerated. 
 
 After the above description, I need say nothing further as to the 
 nature and danger of the disease. The patient perished exactly in 
 the same manner as the infected rabbit. It is not, of course, known 
 how the infection occurred, but if one may judge from the extent and 
 intensity of the disease, it must have been often repeated. In France 
 rabbits are very commonly reared in hutches; and one may there- 
 
 1 Gubler, " Tumeurs du foie de'terminees par des oeufs d'helminthes et comparables a 
 des galles observers chez 1'homme," M6m. Soc. JBioL, 1858, with illustrations, and also 
 Gaz. Md., p. 657, 1858, Paris, or Davaine, " Traite* Entoz., p. 288, 2d ed. As the 
 quotation shows, the true nature of the affection was not recognised. Gubler regarded 
 the Coccidia as eggs of Distormtm, although he sought in vain for the worms, and was 
 unable to decide whether the presence of these reputed eggs were only an aggravation, or 
 the cause, of the tumours. I was the first to recognise the true nature of the parasites 
 (see the first German edition of this work, Bd. i., pp. 49 and 740), and the importance of the 
 case was then for the first time rightly appreciated. 
 
OCCURRENCE OF COCCIDTUM IN MAN. 223 
 
 fore suppose with a certain probability that the patient lived in con- 
 ditions in which he was associated with the animals in such a way 
 that the Coccidia voided in the rabbits' dung were transferred to him. 
 Perhaps he had for a lengthened period drunk from a cistern standing 
 in connection with the rabbits' hutches. 
 
 If we are not mistaken in our supposition as to the mode of trans- 
 mission of the hepatic Coccidia, man may derive them from rabbits 
 by eating substances which have been contaminated by their excre- 
 ment ; and considering the frequency with which these animals occur 
 in our yards and houses, it is very probable that the Coccidia have a 
 wider and more frequent distribution than is generally supposed, 
 though perhaps occurring only in certain localities and in small 
 numbers. 
 
 Nor is this a mere probability. Even in the first edition of this 
 work I was able to report * that Dressier had found Coccidia (Psoro- 
 spermice) in the liver of the human subject. They were enclosed in 
 three cysts about the size of a millet-seed or a pea, which lay close to 
 the periphery of the liver. The character of the contents, as seen in 
 the accompanying reproductions of his figures, left no doubt as to the 
 nature of the tumours (Fig. 114). 
 
 I am indebted to the courtesy of Professor Perls in Giessen for 
 being now able to cite two additional cases. He sent me last No- 
 
 FIG. 114. Coccidia from the human liver A x 330, B and C x 1000. 
 
 vember a drawing and a section which had been made by Professor 
 Sattler in Vienna during a course of pathological anatomy. From 
 both drawing and preparation one could recognise the cross- sect ion 
 of an enlarged bile-duct, with a very proliferous epithelium and with 
 Coccidia. The latter were partly removed from their original position 
 
 1 Loc. eft., p. 740. 
 
224 COCCIDIUM OVIFORME. 
 
 and scattered in groups, so that they looked as if embedded in the sur- 
 rounding connective tissue. Since the contents of the Coccidia were 
 quite clear, as is always the case in preparations mounted in glycerine, 
 the bodies might easily have been mistaken for eggs of Distomum (D. 
 lanceolatum), but in my further examination any doubt as to their 
 true nature was wholly removed. 
 
 The other case was based on a preparation from v. Sommering's 
 collection annexed to the Pathological Institute in Giessen. It showed 
 ulceration of the bile-ducts, in which Coccidia were to be seen. The 
 label bore the words, " An Distomis orta" which perhaps originally 
 read " Distomatis ova." 
 
 But it is not only the liver, but also the intestinal canal, which is 
 invaded by these parasites, and to a greater or less extent affected by 
 them. We know cases, apart in the meantime from man, where not only 
 rabbits, dogs, and cats, but also other mammals sheep, pigs, guinea- 
 pigs, and moles were infested with these intestinal Coccidia. Those of 
 the mouse and others belong, as we have noted, to a distinct species. 
 The same is true of the Psorospermice of fowls, 1 ducks, and geese, 
 which, according to a preparation kindly lent me by Professor Ziirn, differ 
 from mammalian Coccidia in their spherical form, in the thinness of 
 of their shell, and in their smaller size (0'002 mm. in diameter), but 
 agree with them (according to Eivolta) in their life-history. I have 
 myself only studied the intestinal Coccidia of the dog and the cat. 
 In the case of the latter, I could most distinctly convince myself that 
 the Coccidia were contained in the epithelial cells until perfectly ripe. 
 This is much more easily demonstrated than in the case of the hepatic 
 Coccidia, for the intestinal epithelial cells, perhaps because of their 
 opercular structure, have a greater permanency of form, and remain 
 closed even when abundantly infected. 
 
 In the milder cases the Coccidia are sometimes scattered, some- 
 times arranged in groups. In the latter case one can recognise the 
 infected places even with the naked eye as somewhat elevated whitish 
 spots of varying size. There are also cases in which the surface of the 
 intestine is uniformly infected and considerably swollen, so that it looks 
 as though it were overlaid with a false membrane. I found it thus, 
 particularly in a dog which had served for an experiment with Trichina* 
 The parasites are usually most crowded in the villi, which then 
 appear like little white points, as after an absorption of chyle, so that 
 it has even been conjectured that the Coccidia of course, as normal 
 structures might play some part in the absorption of fat. 3 The 
 
 1 The occurrence of Psorospermice in birds was first observed by Rivolta (1869). 
 
 2 In another dog infected with Trichina I found numerous Coccidia in the intestine : 
 Virchow has also made the same observation. 
 
 a Finck, "Sur la physiologic de 1'epithelium intestinale," These Strassbourg, p. 17, 1854. 
 
CHANGES IN THE INTESTINAL MUCOUS MEMBRANE. 225 
 
 Lieberkiilmian glands are not ^infrequently filled with them, and some- 
 times swollen out to double their normal diameter. 1 The surrounding 
 tissue is then infiltrated and inflamed, and sometimes degenerates in 
 small but distinct ulcers. To all appearance this is especially common 
 in rabbits, where (according to Eeincke) the glands of the caecum 
 and of the vermiform appendix very frequently undergo similar 
 alteration. 2 
 
 It is obvious that the changes wrought by these intestinal Ooccidia 
 destruction of the epithelium, swelling, and inflammation of the 
 sub-mucosa, ulceration, &c. cannot be without derangement of 
 function, and in this connection numerous differences in the extent 
 and intensity of the disease will be observed. Dyspepsia, loss of 
 appetite, imperfect nutrition, colic, looseness of the bowels, are the 
 most constant attendant symptoms. 3 In rabbits and mice these are 
 often so aggravated that death ensues. 
 
 As to the phenomena caused by the parasitism of Coccidia in man, 
 nothing really is known, since few instances only have yet been observed. 
 With the exception of Kjellberg and Virchow, 4 Eimer is the only 
 one who mentions the subject. He reports 5 how, in the Pathological 
 Institute at Berlin, he had twice seen bodies in which the intestine 
 was " filled " with Psorospermice similar to those occurring in animals. 
 " In both cases the epithelium of the intestine was for the most part 
 destroyed and riddled by the Psorosperms," just as Eimer had also 
 observed in mice which had died of Gregarinosis. 6 Unfortunately, 
 neither a history of the illness nor an authentic report on the post 
 mortem examination could be procured ; and only this was ascertained, 
 that one of the two men had belonged to the ward for the insane. 
 
 As regards the infection, what I have said of the hepatic Coccidia 
 must hold good here, with this alteration, that it might be brought 
 about by dogs and cats as well as by rabbits. 
 
 1 Lieberkiihn erroneously regarded these glands filled with Coccidia as Psorosperm- 
 tubes, and therefore, with apparent justice, identified the Coccidia as true Psorosperms. 
 " Evolution des Grdgarines, " loc. cit., p. 29. 
 
 2 Reincke reports finding the young stages of these parasites even in the mesenteric 
 glands : " In glandulis mesentericis et in mesenterio secundum vasorum tractum noduli 
 subflavi inveniebantur, quos psorospermia priorum evolutionis graduum impleverant. " 
 Loc. cit, p. 1. 
 
 3 Rivolta found the " Cellule oviforme " frequently in the intestinal villi of dogs which 
 had been killed on suspicion of madness " Studi fatti nel cabinetto di anatom. pathol. di 
 Pisa,'' p. 42, 1877. I have, however, doubts whether this were a case of true Coccidia. 
 
 4 Virchow 's Archiv f. pathol. Anat., Bd. xviii., p. 523, 18 . 
 
 5 Loc. cit., p. 16. 
 
 c " In many parts the intestine contained scarcely anything but epithelial cells, 
 " Psorosperms," or cells, and when these had fallen out from the hardened cross -sections 
 of the intestine, I saw that the wall looked as if small holes had been punched in it, or as 
 if it had been eaten through." Eimer, loc. cit., p. 13. 
 
 P 
 
226 
 
 COCCIDIUM OVIFORME. 
 
 kidney. ( x 320, after Lindemann. ) 
 
 a. Connective tissue fibrils. 
 
 b. Connective tissue corpuscles. 
 
 c. Pseudonavicellae, lying free. 
 (/. Hassall's mucous balls. 
 
 A. Psorosperm- balls. 
 
 Lindemann reports 1 having found Psorosperms even in the human 
 kidney, in the case of a patient who died of Bright's disease in the 
 
 hospital at Nijni Novgorod. The 
 parasites appeared to the naked eye as 
 small brownish-black masses, up to 2 
 mm. in size, which were embedded in 
 great numbers in the tunica serosa, 
 but covered by a thin layer of the 
 same. "In my microscopic examina- 
 tion," Lindemann writes, " these masses 
 were seen to be colonies of Psorosperm- 
 balls, which were embedded in layers in 
 the connective tissue, and surrounded 
 by the fibrous bands which had been 
 FIG. 115. Psorotpermice (?) from bent out of their course by the balls. 
 
 the connective tissue of the human m , 
 
 The cells and fibres of the connective 
 tissue were normal, excepting the 
 bending of the fibres and the spaces 
 thus created, in which the Psoro- 
 sperms lay. Besides this, the organ 
 was infiltrated with a mucous exudation, which contained the well- 
 known mucous balls of Hassall" (Fig. 115). 
 
 In this report one looks in vain for any sure foundation for 
 Lindemann's identification of these structures with Psorosperms. 
 Since this is not forthcoming, we have only the authority of the 
 investigator to rest upon, and this has unfortunately been so much 
 shaken by some of his later investigations, 2 that I am very doubtful 
 whether Lindemann was right in regarding the observed structures as 
 Psorosperm-capsules. 
 
 Still less can I recognise the " colonies of Psorosperm-balls " (Fig. 
 116) which Lindemann found on human hair, and I very much regret 
 that the observations on this point were first recorded in my work, 
 and to some extent with my guarantee. Not that I deny the presence 
 of these structures, for they have often been observed before and since ; 
 I am only opposed to their identification with Psorosperms, and the 
 fanciful history which was afterwards accorded to them. 3 For it was 
 
 1 See the first edition of this work, Bd. i., p. 943, for notice of Lindemann's com- 
 munication to me on the subject. Virchow has also found Psorosperms in the kidneys of 
 the bat ( Virchow' s Archivf. pathol. Anat., Bd. xviii., p. 527, 1860). 
 
 2 I will only refer to the entirely false representation which Lindemann gave of the 
 organisation of JEchinorht/nchus (Bull. Soc. imptr. nat. Afoscou, p. 184 et seq., 1865), and 
 to my critique (Arcfiiv f. Naturgesch., Jahrg. xxxii., Bd. ii., p. 152, 1866). 
 
 8 See Lindemann's statements, Bull. Soc. impfr. nat. Moscou, p. 425 et seq., 1863, 
 and specially p. 282, 1865. 
 
SUPPOSED PSOROSPERMS UPON THE HAIR. 227 
 
 not simply moving Gregarines from which the structures seated on 
 the hair were produced by encystation and spore formation, 1 but 
 
 FIG. 116. Lindemann's Psorosperm -balls (2?) and Gregarines (G) on human hair. 
 
 Gregarines which were transferred to the hair from the intestine of 
 the louse, and which had Psorosperms of such power of resistance 
 that even the coiffures of ladies were infected with potentially active 
 germs, from which these Gregarinoid creatures escaped, and, wandering 
 into the body of their host, became again Psorosperms in the most 
 varied organs, and gave rise to manifold troubles. 
 
 Although coiffures have been absolved from all complicity in the 
 production of " Gregarinosis," it is nevertheless quite possible that our 
 experience as to the pathological nature of the Psorosperms is not yet 
 by any means complete. Thus Zurn has lately come to the conviction 
 that the infectious virulent influenza of the rabbit an often fatal 
 rhinitis, which usually spreads rapidly from the nose to the pharynx 
 and tympanum, and, after perforation of the membrane, sometimes 
 attacks the external ear or passes to the intestine is caused by para- 
 sites, 2 which can be observed in great numbers as naked Gregarines 
 and Psorospermice in the affected mucous membranes and their 
 secretions. Similarly Silvestrini and Rivolta were able in 1872 
 to refer an epidemic prevalent among the fowls around Pisa to 
 Psorosperms. 3 The disease was localised, like the influenza of the 
 rabbit, in the pharynx, larynx, and nose, but sometimes affected the 
 conjunctiva, intestine, or even the comb. The observers saw that 
 
 1 Knoch, who investigated Lindemann's hair Psorosperms in Russia, certainly had 
 the same structures under observation, but never found mobile forms (Journal des rus- 
 sischen Kriegsdepartements, Bd. xcv., 1866). 
 
 2 " Die kugel- und eifb'rmigen Psorospermien'als Ursache von Krankheiten bei Haus- 
 thieren," p. 14, Leipsig, 1878. The infectious catarrh of rabbits is described as a fungoid 
 disease in Von Schmidt's work, "Die mycotischen Erkrankungen der Respirationsorgane, 
 apeciell der Kaninchen : " Hofgeismar, 1877. 
 
 3 Giomale di anatomia, fisiologia e pathologia degli animali, Pisa, 1873 ; see also 
 Rivolta, "Tarass. veget.," p. 390. 
 
228 INFUSORIA. 
 
 the epithelial cells (in the comb, the epidermal cells, as far as the Mal- 
 pighian layer) were penetrated and altered by Coccidia, and that the 
 subjacent tissue was swollen and inflamed, so that the animals were 
 for the most part starved or suffocated. The nature of the disease 
 was placed beyond all doubt, not only by observation, but also by 
 experiment, of which, however, the constant result was that, as before 
 mentioned, only the Coccidia with segmented contents caused infec- 
 tion, while the younger stages traversed the intestine passive and 
 harmless. 
 
 In conclusion, I must once more repeat that the true Coccidia do 
 not include all the forms which investigators of the higher animals 
 have considered Psorospwmice and designated as such. Among the 
 latter I would, for instance, class the "green" Psorospermice,* which 
 Paulicki describes in apes, and which were found in the lungs both 
 of adult and of newly born animals. Their chlorophyll contents 
 are sufficient to exclude them from the Coccidia. 
 
 CLASS III. INFUSORIA. 
 
 Ehrenberg, "Die Infusionsthierchen als vollkommene Organismen : " Leipzig, 1838. 
 
 Dujardin, "Histoire naturelle des Infusoires : " Paris, 1841. 
 
 Claparede et Lachmann, "Etudes sur lea Infusoires," Parts i. et ii. : Geneve, 1858-61. 
 
 Stein, "Der Organismus der Infusorion," Th. i.-iii. : Leipzig, 1867-1878. 
 
 Biitschli, " Ueber die Conjugation der Infusorien," in " Studien iiber die ersten 
 
 Entwickelungsvorgange der Eizelle, die Zelltheilung, und die Conjugation der 
 
 Infusorien : " Frankfurt, 1876. 
 
 Protozoa with a more or less definite body-form, and provided with 
 cilia, which are placed on the body in varying member and arrangement. 
 The protoplasm, especially of the higher forms, is differentiated into an 
 outer layer and a central mass, which sometimes encloses a single nucleus, 
 sometimes more, and very generally one or more contractile vacuoles. 
 With the exception of some parasitic species, all of them have a mouth, or 
 one or more mouth-like openings, serving for the ingestion of food, and 
 most of them have also an anus. 
 
 The name " Infusoria," which has been a familiar word for more 
 than a hundred years, is used to denote those organisms discovered 
 by Leeuwenhoek, which are constantly found in organic infusions, 
 in which indeed they were thought to be spontaneously generated. 
 This is not, however, their proper or normal habitat, which is rather 
 to be sought in stagnant or sluggish water, while its countless micro- 
 scopic contents furnish a rich supply of nourishment to these minute 
 
 1 " Beitrage zur pathol. Anat.," p. 61, 1872. 
 
MOVEMENTS AND MODE OF LIFE. 229 
 
 organisms. In the economy of Nature this fact is of pre-eminent 
 importance, for by the invisibly active life of these organisms a large 
 quantity of organic substance, which would otherwise be lost to the 
 animal world, is appropriated and utilised, and the more fully inasmuch 
 as in wealth of form the Infusoria are second to no other group, and 
 in number of individuals largely exceed all others. The latter state- 
 ment is specially true of the putrefactive Infusoria, for these are 
 found along with fungi and Schizomycetes, in a truly astounding 
 multitude, wherever there is any abundant putrefying substance in 
 the water. It is therefore not surprising to learn that numerous 
 forms have found a fit environment in the intestine, and especially 
 in the rectum of living animals. 
 
 The Infusoria are most conspicuously separated from other Pro- 
 tozoa by the possession of cilia and an oral aperture, two structures 
 in this case naturally associated together since the body has not only 
 a more or less firm cuticle which prevents the formation of pseudo- 
 podia and amoeboid ingestion, but has also very generally a firmer 
 cortical layer, which encloses the less dense protoplasm and the 
 abundant remains of food. 
 
 By means of their cilia, the Infusoria have the power of swimming 
 somewhat rapidly, though there are species which, after a longer or 
 shorter free life, become attached to some foreign object. Some of 
 these the so-called Acinetce even lose their cilia after becoming fixed, 
 so that their true nature is easily overlooked, especially since, instead 
 of a mouth, they have a large number of openings mounted on long 
 thin tubular stalks, which enable their bearers to catch and suck the 
 juices of other small animals, mostly Infusoria. 
 
 In this world of invisible life, moreover, these predaceous forms 
 lead on to others, which are parasitic. Besides the free Acinetce, 
 there are also other Suctoria, which, instead of killing their prey 
 usually larger ciliated Infusoria only bore their way into them, and 
 live there as parasites. They grow at the expense of their host, and 
 by repeated division produce a numerous progeny, which, on reaching 
 maturity, break through the body-wall, swim about for some time by 
 means of their cilia, and finally return again to an Infusorian host. 1 
 
 The Cilia exhibit such great and characteristic differences in 
 number and arrangement, that these have been used, not without good 
 results, for systematic purposes. Sometimes the whole surface of the 
 body, sometimes only certain parts, are provided with cilia, and their 
 
 1 These parasitic forms have attained a somewhat unhappy prominence in the history 
 of our knowledge of the Infusoria, since they have given rise to the idea that the ciliated 
 Infusorians were viviparous, and produced ".4 cine to -like embryos" (Stein). The para- 
 sitic nature of these so-called embryos has, however, been experimentally established ; see 
 Butsohli, Zcitschr. f. wiss. Zoo/., Bd. xxv., p. 426, 1875. 
 
230 INFUSORIA. 
 
 number is in the latter case generally small. In a large and rich 
 group the Flagellata there is usually only a single flagellum, or at 
 most but a few. 
 
 It is especially the region round the mouth which in such cases 
 bears the cilia, and this is intelligible when we remember that the 
 cilia act not only as locomotor organs, but also in capturing the food. 
 A little whirlpool is set up by their movements, and the minute 
 bodies suspended in the water are swept into the mouth. For this 
 purpose the oral cilia often have a special arrangement, and a more 
 vigorous development than those on other parts. of the body. 
 
 The food, which usually consists of fine granules, becomes agglo- 
 merated into a round ball at the lower part of the mouth, and this is 
 swallowed only when it has attained a certain size. It is of course 
 the adjacent parts of the contractile cortical layer which effect this 
 swallowing, and transfer the morsel through a sort of gullet (of course 
 without special walls, and really only a slit in the parenchyma) into 
 the central substance. Some specimens living in favourable nutritive 
 conditions often have their central substance filled with numerous balls 
 of food. Organic pigments, such as carmine and indigo, are similarly 
 ingested, and were first described in 1777 by Baron von Russworm- 
 Gleichen in a work on microscopic objects. l The food-balls, under the 
 pressure of the surrounding body-substance, glide inwards in more or 
 less regular courses, and here and there coming in contact, they flow 
 together ; and one can follow step by step the various changes which 
 they undergo under the action of the juices mixed up with them, 
 until finally the remnants are expelled by the anus. This lies usually 
 at the posterior end of the body, opposite the mouth, though there are 
 instances in which the anus is near the oral end, and in which the 
 mouth is displaced, and comes to open near the middle of the body. 
 
 When the food does not consist of fine granules, as is the case in 
 some Infusoria, but of larger bodies (plants and animals), the mouth is 
 usually a very wide and extensible cleft, which extends over a con- 
 siderable proportion of the whole body. 
 
 An Alimentary Canal is never present ; nor are the numerous 
 " stomachs " described by Ehrenberg (hence the name " Polygastrica ") 
 anything more than the food enclosed in vacuoles of the body-substance. 
 What has been previously said of the Rhizopoda holds true of the 
 Infusoria, which only differ in the persistence of the openings for 
 ingestion and expulsion ; and we have already mentioned that these 
 openings are sometimes wanting. So far as we know, however, this 
 occurs only in certain parasitic forms (species of the genus Opalina), 
 which, living continually surrounded by fluid nutriment, require only 
 
 1 " Mikroskopische Augen- und Gemuthsergotzungen," 1777. 
 
DIFFERENTIATION OF THE BODY-SUBSTANCE. 231 
 
 power of absorption through the outer membrane. It is extremely 
 improbable that this mode of nutrition occurs in any free-living form, 
 although it is often so alleged. Albuminoid solutions soon putrefy, 
 and never occur around living organisims in a state which would 
 ensure all the properties essential for the nutrition of an animal ; so that 
 if they feed by imbibition, it must be on inorganic substance ; in other 
 words, they must be referred to the vegetable kingdom. A free-living 
 animal requires the power of incorporating a firm (i.e., resisting) 
 organic substance, and therefore, when a cuticle and cortical layer are 
 present, it requires a mouth. 
 
 The Cortical Layer is, as we have indicated, the special seat of the 
 animal functions. This is proved not only by direct observation, but 
 by the fact that in the larger forms a striation is sometimes seen 
 resulting from a layer of fibrils. This occurs, for example, in the stalk 
 of the familiar bell-animalcule ( Vorticdla), and presents a distinctly 
 muscular appearance. The course of the fibrils always corresponds 
 with the direction in which the contraction takes place, and is pre- 
 dominantly longitudinal. 
 
 To this cortical layer belong the vacuoles, which, in the Infusoria, 
 usually occur at distinct places, and which, by their more or less 
 frequently repeated rhythmic contractions, convey the impression of 
 hearts. The resemblance is further increased when sometimes special 
 lacunae are found in connection with the pulsating space, as vessels 
 with the heart. These are especially visible at the moment of systole, 
 when the fluid contained in them is in a state of tension, and their 
 observation is as easy as it is beautiful, e.g., in the common slipper- 
 animalcule (Paramcecium aurelia). After contraction the fluid often 
 collects in little isolated drops, which afterwards flow together into a 
 larger vacuole. This is a certain proof that the vacuoles have no in- 
 dependent surrounding membrane, but owe their contractility solely 
 to the surrounding cortical layer. Their contractility varies consider- 
 ably in different species, being sometimes rapid and frequent, and in 
 other cases slow and at long intervals. Even in the same individual 
 differences are observable at different times and states ; but this may 
 at least be said, that in general the liveliness of the pulsations is pro- 
 portionate to the general energy of the animal and the temperature of 
 the surrounding medium. 
 
 Our decision as to the functional import of this apparatus de- 
 pends very essentially on the fact that in several cases it has been 
 most distinctly proved that it communicates with the exterior by an 
 opening, sometimes temporary, sometimes permanent, and rarely by 
 the anus. 1 Thus the contractile vacuole of the Infusoria so closely 
 
 1 See especially Wrze'sniowski, Archivf. mikrosk. Anat. t Bd. v., p. 25, 1869. 
 
232 INFUSORIA. 
 
 resembles the excretory apparatus of the flat-worms, that we need 
 hardly scruple to claim for it a similar excretory function, and regard 
 it as expelling the superfluous water and the waste products of 
 metabolism. 
 
 The Nuclei, as well as the contractile vacuoles, lie in the cortical 
 layer. This is especially the case with the nucleus par excellence, 
 which is seen usually, even on superficial observation, and still better 
 after the use of acetic acid, as a conspicuous, firm body, sometimes 
 showing a division into two or more parts of round, elongated, or 
 occasionally ribbon or garland -like form, and whose resemblance 
 to a ordinary cell - nucleus first suggested the idea that the In- 
 fusoria were unicellular organisms. But even von Siebold found 
 besides this nucleus, and generally closely adjacent to it, the so-called 
 " nucleolus " a sharply defined, minute, shining body more than one 
 sometimes being present, although it has not been demonstrated in by 
 any means all the species. 
 
 Both bodies are not only of high importance in determining the 
 morphology of the Infusoria, but have been the subject of much dis- 
 cussion and study during the gradual development of our knowledge 
 of the reproductive process in the Infusoria. For a while the opinion 
 seemed plausible that these two structures represented the sexual 
 organs. This theory was especially based on the observations and 
 conclusions of Balbiani, 1 and was very generally accepted, 2 especially 
 as it seemed in a satisfactory way to sum up a series of more or less 
 unco-ordinated results. 
 
 According to the theory supported by Balbiani, the nucleolus is 
 the male reproductive gland in its undeveloped state, and the nucleus, 
 which Ehrenberg had previously called the " testis," is, indeed, the 
 ovary. 3 Appearances are certainly in favour of such a theory. One 
 sees the nucleolus swell up under certain circumstances, and become 
 a long vesicle, whose contents gradually assume a striated appearance, 
 as if they were a bundle of spermatozoa. 4 While the nucleolus under- 
 goes these changes, and finally divides into a number of balls, re- 
 sembling sperm-capsules, the nucleus, which is meanwhile much 
 enlarged, also falls asunder into a number of round masses, which 
 
 1 " Recherches sur les phe'nomenes sexuels chez les Infusoires," Journal dc physiologic, 
 t. iv., 1862. 
 
 9 The account given of the sexual reproduction of the Infusoria in the first edition of 
 this work owed its origin to the influence of this theory. 
 
 3 According to Ehrenberg, the sperms gained the exterior by means of the "con- 
 tractile bladder," which thus became a sort of seminal vesicle. 
 
 4 Joh. Mxiller, Lieberkuhn, and Claparede and Lachmann had remarked this appear- 
 ance before Balbiani, and had noted the likeness between the threads and spermatozoa, 
 without, however, identifying the two. 
 
EXISTENCE OF SEXUAL PROCESSES. 233 
 
 might well be regarded as ova, and which Balbiani, indeed, credited 
 with all the properties of such structures. 
 
 According to Stein, who in general supported this theory, the eggs 
 develop inside the maternal body, and the resulting embryos, for 
 which he mistook the above-mentioned parasitic Suctoria, leave the 
 mother in the form of Acinetce. On the other hand, Balbiani alleged 
 that he had repeatedly observed the laying of these " eggs," and he 
 therefore regarded the Infusoria as oviparous animals. 
 
 What still further increased the resemblance between these pro- 
 cesses, thus shortly summarised, and the phenomena of sexual 
 reproduction, was the fact that they were preceded by a veritable 
 copulation. 
 
 Even Leeuwenhoek believed that he had seen his Infusoria 
 in the act of pairing. Other investigators, like Russworm-Gleichen 
 and 0. F. Miiller, asserted the same thing, but their results fell into 
 discredit, and were forgotten, when Ehrenberg and Dujardin explained 
 the phenomenon as a peculiar case of the longitudinal division which 
 they had so frequently demonstrated among the Infusoria. At any- 
 rate, the credit is due to Balbiani of having recognised that the con- 
 jugation of two originally distinct individuals was an actual fact. In 
 this act the two animals lie together with their mouths in contact, 
 not only superficially, as Balbiani would have it, but so intimately 
 that the connecting parts are sometimes absorbed, and the animals 
 form a double body for several days. Balbiani interpreted this as an 
 act of copulation, in which the sperms were mutually exchanged. 
 Stein 1 also recognised a distinct association between the copulation 
 and the reproduction of Infusoria, but refused to regard the act as an 
 actual fecundation. He considered it as analogous to the conjugation 
 of certain lower plants a process which seems to bring to maturity 
 the hitherto inactive and undeveloped sexual organs, or so to change 
 them that a subsequent (self) fertilisation 2 becomes possible. He 
 supports this opinion by observations, according to which the sperms 
 became ripe as a rule, only after the separation of the conjugating 
 individuals a fact in direct antagonism to the theory of actual co- 
 pulation. He further cites cases in which the conjugation (" Syzygie," 
 Stein) leads to a complete and inseparable union of the two individuals. 
 
 These relations began to assume a somewhat changed complexion 
 in the light of the facts advanced by Bittschli, which excluded any com- 
 parison with the processes of sexual reproduction, and furnished new 
 
 1 At least in the second volume of the researches above referred to. 
 
 2 It is striking that Stein speaks only of a fertilisation of the nucleus of the embryonal 
 sphere, which performs the functions of an ovary, and not of the egg-like bodies which 
 result from this by segmentation. 
 
234 INFUSORIA. 
 
 and very cogent reasons for the comparison of the Infusorian body with 
 a cell. The investigations of this excellent observer prove that changes 
 of the nucleolus, quite similar to those above described, may often 
 be observed in the nuclei of ordinary dividing cells and segmenta- 
 tion masses. The ordinary supposition that in division the nucleus of 
 the cell simply separates into two parts was shown to be a mistake, due 
 partly to the variable and often unfavourable condition of the material 
 examined, but much more to the minuteness of the object and the use 
 of insufficient microscopic power. In reality the process is a compli- 
 cated one, accompanied by a transformation of the contents, which 
 essentially resembles the formation of nuclear fibres in the Infusoria. 
 After this phenomenon was once recognised, it was repeatedly observed 
 with various modifications in the most diverse kinds of cells (also by 
 Strasburger in vegetable cells), and was in fact proved indubitably to 
 be of general occurrence. The apparent " sperm-balls " were therefore 
 divided nuclei, which afterwards reassume a homogeneous nature, and 
 the so-called " sperms " were anything but what Balbiani and Stein l 
 had supposed. 
 
 The Nucleolus of the Infusoria is thus a structure which, in its 
 essential morphology, coincides with the nucleus of the ordinary cell, 
 and may therefore be justly identified with it. It is not, then, sexual 
 maturity which finds expression in its transformation, but simply the 
 commencement of division, which, as a matter of fact, follows close 
 upon the process of conjugation. This mode of multiplication is not, 
 however, confined to the time immediately following conjugation. It 
 also occurs later, but happens most frequently and constantly in those 
 forms which have previously conjugated. So far as we know, this 
 process and its modifications (including budding) is the only mode of 
 reproduction exhibited by the Infusoria. 
 
 But if, as we have maintained, the " nucleolus " represents the 
 nucleus of the Infusorian body, what, then, is the " nucleus " to which 
 this position is usually accorded ? Again the process of conjugation 
 sheds light on the question. The observations on this point, especially 
 of Blitschli, inform us of the surprising fact that the portions of the 
 "nucleus" are indeed, as Balbiani affirmed of his "eggs," generally 
 expelled during conjugation, without, indeed, ever forming new indi- 
 viduals. Instead of this expelled " nucleus," another is formed, and 
 that from one of the newly originated " nucleoli." Sometimes the 
 portions of the " nucleus " are not wholly expelled, and then the new 
 " nucleus " results from a fusion of the remainder with a " nucleolus." 
 
 1 To establish the theory of these investigators it would have been necessary to prove 
 that the sperms resulted from cells. But no one had tried to discover a cellular struc- 
 ture in the nucleolus. 
 
FATE OF NUCLEUS AND NUCLEOLUS IN COPULATION. 235 
 
 There can be no doubt that both " nucleus " and " nucleolus " 
 have the function of a cell-nucleus. The Infusorian is, in other words, 
 provided with two quite different nuclei (a " principal nucleus " and an 
 " accessory nucleus "), both of which undergo at certain times (during 
 conjugation) a fundamental transformation and renewal. 
 
 That the " nucleus " is really of the nature of a true cell-nucleus 
 is proved by the fact that under certain circumstances it also exhibits 
 the same changes as we have previously described in the case of the 
 " nucleolus." We know especially of some Infusoria in which con- 
 jugation has not yet been observed (Spirochona, Podophrya, Dendro- 
 cometes). Here it is not the "nucleolus" but the "nucleus" which 
 assumes a fibrillated character before division, and afterwards (in its 
 parts) reassumes its former state. Similarly, the later divisions in 
 Infusoria take place without change in the " nucleolus." It is only 
 the " nucleus " which participates in these processes, and falls (whether 
 with antecedent striation or not is still uncertain) into two equal parts, 
 one for each of the twin parts. 
 
 The above observations sufficiently prove that conjugation is 
 of some consequence in the reproductive processes of the Infusoria. 
 It is, however, no sexual copulation; it can hardly be said to be 
 anything but a fertilisation, 1 as we have already hinted. At 
 any rate, the act is no concurrence of sexual products, but of living 
 individuals of individuals, however, which, like the sexual products, 
 are morphologically equivalent to cells, and as such represent in one 
 the various organs, tissues, and also sperms and ova of the higher 
 animals. We are confirmed in this opinion by the fact that 
 there are Infusoria (Vorticellce) in which conjugation never or seldom 
 occurs between individuals of equal size and similar form, but 
 between a large fixed animal and a much smaller young form, 
 which originates in consequence of a rapidly repeated division, and 
 stands in exactly the same relation to the fixed form that the micro- 
 gonidium bears to the macrogonidium in certain Algse a relation 
 which, in the case of the latter, had for long been jv.stly regarded by 
 botanists as equivalent to fertilisation. 
 
 Conjugation is further of great importance in connection with the 
 Infusoria since the subsequent divisions occur much more frequently 
 than would otherwise be the case. It therefore obviously serves, like 
 genuine fertilisation, for " freshening the blood." It marks, to some 
 extent, the beginning of a reproductive period, during which multi- 
 
 1 This being the case, we may note the great interest attached to the resemblance 
 between the fate of the nucleus in conjugating individuals and the changes of the germinal 
 vesicle which accompany impregnation, especially as described in the recent researches of 
 Hertwig, Fol, Biitschli, and others.. [See Geddes, article "Reproduction," " Encycl. 
 Brit.," Edinburgh, 1885. W. E. H.] 
 
236 INFUSORIA. 
 
 plication takes place exclusively by division, until exhaustion renders 
 another conjugation imperative. 
 
 Fission in the majority of Infusoria is transverse, so that the 
 anterior part has to form a new anus, and the posterior part a new 
 mouth and the associated circlet of cilia. In other cases the division 
 is longitudinal, and it may even take place diagonally. Nor is it by 
 any means necessary that the two parts should be equal ; indeed, the 
 one is often so very minute that it looks like a little bud. When the 
 division is repeated in quick succession, the resulting organisms are 
 of extraordinary minuteness, which is particularly seen in the fixed 
 forms as long as the progeny remain connected together in a group. 
 
 In many species the division only takes place after the mother- 
 animal has drawn itself together into a ball and donned a capsule. 
 Sometimes two, sometimes four, six, or eight young Infusoria result, 
 which remain within the capsule till they break through it, and con- 
 tinue their life outside. 
 
 This encystation occurs for other purposes than that of reproduc- 
 tion. At other times also the Infusoria have the power of secreting a 
 cyst and passing into a quiescent state. This may be observed on 
 approaching scarcity of water, or when the environment is in some 
 way abnormal. It takes place indifferently in adult and young forms. 
 Protected by this cyst, which is often thick and very resisting, these 
 very delicate creatures can survive complete dessication. They may 
 be kept, like seeds or eggs of worms, for years, and yet, on the appli- 
 cation of water, often recover their full vital energy within a few 
 hours, and break through the capsule. The importance of this for the 
 Infusoria is very obvious. It is not only a means of preservation, but 
 of propagation ; for the wind, passing over the dried up ditches, lifts 
 the capsules and carries them to great distances, dropping them again 
 in most varied situations on leaves, moss, and bark, in chinks, 
 bowls, and infusions. Such germs have been repeatedly demonstrated 
 by Ehrenberg and others in atmospheric dust, by passing the air 
 through pure water. We do not require to point out how this habit 
 is specially favourable to the parasitic occurrence of these animals. 
 
 If the Infusoria be carried to, or in any way reach, a situation and 
 environment which fulfil the conditions of their life, they multiply so 
 rapidly that their number increases in a short time to an almost in- 
 credible degree. Theoretical calculations which have been made give 
 results on this matter not less astounding than those above quoted for 
 the Schizomycetes. 
 
 In reference to the manifold and fundamental differences between 
 the various forms of Infusoria, we may note that the group is generally 
 divided into "Flagellate" with a flagellum, and "Ciliata" with cilia. 
 
ORGANIZATION OF THE FLAGELLATA. 
 
 237 
 
 The latter are at once most numerous, most highly developed, and 
 most manifestly animals, while the Flagellates recall in many ways 
 certain vegetable organisms, and often approach the unicellular Algae 
 so closely in structure and life-history, that a separation can only be 
 based on the decidedly animal mode of their nutrition. Many Fla- 
 gellata also resemble very closely the swarm-spores of certain Ehizo- 
 poda. 
 
 Both groups include numerous parasitic forms, which infest both 
 the lower and higher animals, including man. 
 
 Order I. FLAGELLATA. 
 
 [Davaine, Art. ' ' Monadiens, " "Diet. sci. me*d.," 1874. R. L.] 
 
 Stein, " Organisraus der Infusionsthiere," Abth. iii., 1878. 
 
 Blitschli, " Beitrage zur Kenntniss der Flagellaten, " Zeitschr. f. wiss, Zool., Bd. xxx., 
 pp. 205 et seq., 1878. 
 
 Dallinger and Drysdale, ' ' Researches on the Life-history of the Monads," Monthly 
 Micr. Journ., vols. x.-xiii., loc. div., 1873 to 1876. 
 
 [Grassi, " Intorno ad alcuni protisti Endoparassitici," Atti Soc. Ital. sci. natur., vol. 
 xxiv., p. 47, 1882. R. L.] 
 
 Infusoria of small size, and ivith but slight differentiation of the 
 body-parenchyma, so that the cortical layer and central mass are only 
 faintly contrasted, and a nucleolus can only rarely be distinguished. The 
 cilia are always confined to the anterior oral extremity, and are present 
 either singly or in small numbers. Sometimes there is also a ciliated 
 fringe surrounding the mouth like a collar, or running down the body in 
 the form of a longitudinal band. An anus seems always to be wanting. 
 
 FIG. 117. Cercomonas muscce at different 
 stages. (After Stein.) 
 
 FIG. 118. Bodo saltans. (After 
 Stein.) On the right an instance of 
 division. 
 
 Of the numerous and often very wonderful and elegant forms of 
 flagellate Infusorians, we are here specially interested only in those 
 
233 FLAGELLATA. 
 
 which belong to the family Monadinse. These creatures are, as their 
 name suggests, almost at the extreme limit of visible organisms ; they 
 are extremely small and transparent, and have generally very few, but 
 long, cilia (Figs. 117, 118), which sometimes propel the body rapidly 
 about, and sometimes merely vibrate to and fro. A slight amoeboid 
 movement is also occasionally to be observed. Almost all these Infu- 
 soria live on putrefying substances, and are often found in countless 
 numbers in water, or in living animals, especially in the rectum. 
 The species most familiar to us are those always present in myriads 
 in the large intestine of frogs and toads. In warm-blooded animals 
 the Monadinae are also among the most frequent of parasites. It is, 
 for instance, impossible to examine any ruminant or pig without find- 
 ing these creatures in countless numbers, along with other infusorial 
 parasites, in the paunch of the former, and in the ccecum of the latter. 1 
 In order to observe them, it is of course necessary that the examina- 
 tion should take place as soon as possible after death, since they soon 
 perish, and are then scarcely distinguishable from other small bodies. 
 Their occurrence in man, although not exactly rare, appears to be 
 always due to special circumstances, but when they occur it is usually 
 in great abundance. Their presence would also be much more fre- 
 quently ascertained if the evacuations could be immediately examined, 
 or even if it were possible always to use a warm stage. By this means 
 it is possible to keep the parasites alive for many hours, and to ob- 
 serve them in lively motion, if only care be taken that the preparation 
 does not dry up. 2 Slightly acidified water appears to be the best means 
 of moistening them, and is even capableof reviving theirflagging motion. 
 Temperatures above 50 C. and below 14 C. prove fatal, and thus the 
 fact is explained that parasites occurring in winter die in a few minutes, 
 especially if a cold glass slide be used. Further, as these creatures are 
 very sensitive to solution of corrosive sublimate, and perish imme- 
 diately when exposed to it, even when extremely dilute, this drug 
 would probably furnish a very efficient remedy for them. 
 
 The parasitism of the Monadinse is, however, by no means confined 
 exclusively to the Vertebrata. In the genital canals of the snail, in 
 the body-cavity of the Kotifera, and in the alimentary canal of mille- 
 pedes and insects they are not at all uncommon, and occasionally are 
 
 1 Gruby and Delafond have also observed Monadinse in the stomach of the dog 
 (Comptes rendus, t. xviL, p. 1304, 1843), and Davaine in the alimentary canal of the 
 guinea-pig, of the hen, and of the duck (loc. cit. ). [Grassi has recently described similar 
 forms in the guinea-pig, mouse, and duck (loc. cit.). R. L.] 
 
 2 [Grassi (loc. cit.) refers the rapid death of the parasitic Monads, not so much to the 
 fall in temperature, as to the rapid formation of acids in the evacuated faeces. Where this 
 is prevented, the Monads may remain alive for many days. R. L.] 
 
CERCOMONAS AND TRICHOMONAS. 
 
 239 
 
 even so frequent (especially in moths and flies) that whole tracts of 
 the intestine are filled with them. 
 
 Eeproduction is effected by division, which generally takes place 
 longitudinally, and is often so rapidly repeated that the young ones 
 remain for a time grouped close together. Dallinger and Drysdale 
 have also observed conjugation in the Monadinse. This is followed by 
 an encystation, in which the contents break up, and become moveable 
 germs, or countless, immeasurably small spores, which afterwards be- 
 come new Monadinse, and even at high temperatures (above 100 C.) do 
 not lose their power of further development. In individual cases other 
 
 FIG. 119. Trichomonas batrachorum. (After Stein.) 
 
 observers have also noted a quiescent state, which leads to the pro- 
 duction of countless little swarm-spores. 1 
 
 The flagella, which vary very much in number and arrangement, 
 furnish us with the best standpoint from which to consider the indi- 
 vidual characteristics of the various genera. But since a very strong 
 magnifying power is necessary to establish the exact nature of these 
 conditions, many mistakes have been made, which have been specially 
 disastrous in the identification of the species occurring in man. The 
 latter belong, so far as we accurately know them, to two very widely 
 distributed genera, Oercomonas and Trichomonas. The former of 
 
 1 [Recently the independence of the Monads (at least of the parasitic forms) has been 
 several times questioned, and the attempt has been made to regard them as swarming 
 conditions of Amcebce, especially in Cunningham's paper (Quart. Journ. Micr. Sci., N.S., 
 vol. xxi., p. 234, 1881). The Cercomonads are said, after encapsulation, to become A mcebce, 
 which fuse together in large numbers after losing their power of movement, and form 
 considerable masses or even true sporangia. I?. L.] 
 
240 
 
 FLAGELLATA CERCOMONAS. 
 
 these contains numerous free-living species, while the latter is wholly 
 parasitic (in both higher and lower animals). The figures above 
 (Fig. 117) represent Cercomonas muscce, a parasite often found in 
 abundance in the chylific stomach of the house-fly, and also (Fig. 119) 
 Trichomonas batracJiorum from the cloaca of the frog. They show 
 
 FIG. 120. Hexamita intestinalis, in the young and adult states. 
 (After Stein.) 
 
 veiy distinctly the differences between the species in question, yet 
 even lately they have been more than once confounded. Along with 
 T. batrachorum, and hardly distinguishable from it with a low power, 
 there very often occurs another parasite, belonging to the genus 
 Hexamita, which I also figure for purposes of comparison (Fig. 120). 
 
 Cercomonas, Dujardin. 
 
 Bodo, Ehrenberg, and others. 
 
 Monadince, with an oval or lonyish body, which is generally nar- 
 rowed posteriorly, and often prolonged into a terminal filament ; while 
 anteriorly it is provided with a long and thin simple flagellum. 
 
 Cercomonas differs from the related genera, Monas and Bodo 
 (sensu stricto), chiefly in the simplicity of its ciliary apparatus. At 
 the base of the flagellum Monas has two short and fine hairs, which 
 
 1 Grasai, loc. cit., pp. 12-22. 
 
CEECOMONAS. 241 
 
 are always in motion, while Bodo (Fig. 118) is provided with a second 
 long flagellum, which is of a more rigid nature, and is generally 
 directed backwards. 
 
 Each of these three genera contains forms which are said to occur in 
 man. So at least we learn from Steinberg's microscopic researches on 
 the white substances often found between human teeth. 1 For, besides 
 various Vibriones and the above-mentioned Amceba buccalis, he found no 
 fewer than nine different species belonging to the genera in question 
 Monas crepusculum, Ehrbg., M. globulus, Duj., M. lens, Duj., M. elongata, 
 Duj., Bodo socialis, Ehrbg., B. inteslinalis, Ehrbg., Cercomonas biflagellata, 
 Stbg., 0. acuminata, Duj., C. globulus, Duj. As I have had no oppor- 
 tunity of studying this memoir, which is but little known in Germany, 
 I can offer no opinion as to the extent to which these forms really differ, 
 nor as to the accuracy with which they are defined. But I think it 
 necessary to point out that the species mentioned by Steinberg have 
 hitherto, with few exceptions, only been observed living freely (Monas 
 globulus even in sea-water). Although this fact as to the known 
 mode of life of Monads by no means excludes a more or less frequent 
 parasitic occurrence, it appears to me in the meantime questionable, 
 especially considering the extreme difficulty of investigation and 
 determination, whether we are justified from these data alone in 
 reckoning the forms mentioned as human parasites. Yet Steinberg's 
 researches are sufficient to prove that the cavity of the human mouth, 
 with the putrefying organic remains and deposits between the teeth (in 
 caries also in the interior), may be a fertile breeding-place for Monads. 
 The same holds true, as we shall afterwards see, in regard to the genus 
 Trichomonas. 
 
 Not less doubtful than the above forms are those Monads identified 
 by Wedl as Bodo saltans, Ehrbg. (O006 mm., Fig. 118), and Monas 
 crepusculum, Ehrbg. (0*004 mm.), which are described by him as 
 occurring often in great numbers upon unhealthy ulcers. 2 
 
 Another Monad Bodo urinarius 3 which, according to the state- 
 ments of Hassall, occurs very often in cholera patients, but only in 
 albuminous alkaline urine, or along with Vibriones, can as yet hardly be 
 accurately determined. It is described as an oval or round granular 
 body of 0-0012 mm. in length and 0'0007 mm. in breadth, which moves 
 quickly by means of two (sometimes three, or only one) flagella, 
 and multiplies by division. Monads should only rarely be found in 
 normal human urine, since it is only the intermingled organic sub- 
 
 1 Walter's Journal of Modern Medicine, Nos. 20-24, 1862 (Russian), Kief. 
 
 2 " Grundziige der pathol. Histologie," p. 796. 
 
 3 "General Board of Health," London, p. 293, 1855, and Lancet, Nov. 1859, 
 Schmidt's Jahrbiicher, Bd. cix., p. 157, 1861. 
 
 Q 
 
'24'2 CEKGOMONAS INTESTINALIS. 
 
 stances which make the existence of these parasites possible. But as 
 such admixtures are more frequently found in the urine of animals 
 (as Leeuwenhoek has shown in the case of the horse), the presence of 
 these creatures is by no means rare in fresli urine. 
 
 Of all the parasitic forms described as occurring in man, there is 
 only one which we know with tolerable accuracy Cercomonas in- 
 testinalis. It is by no means identical, however, with Trichomonas 
 (Fig. 119) and Hexamita (Fig. 120), mentioned by Ehrenberg and 
 Dujardin as belonging to the same species, and already referred to 
 as living in the cloaca of frogs and newts. Further, all the human 
 parasites found in diarrhcetic stools, and described as Cerconwnas in- 
 testinalis, do not, as we shall afterwards see, really belong to this 
 species. 
 
 Cercomonas intestinalis, LambL 
 
 Davaine, Comptes rendus Soc. biolog., 1854, " Traite* des Entozoaires Synops.," ed. 2, 
 p. xxiii.. 1854 (Cercomonas hominis). 
 
 Ekeckrantz, "Bidrag till kannedomen om de i menniskans tarmkanal fb'rekommande 
 Infusorier," Nordisk med. Arkiv, Bd. i., No. 20 (Virchow-Hirsch, Jahresber., Bd. i., p. 
 202, 1869). 
 
 Tham, "Tvanna fall af Cercomonas," Upsala Idkare Foren. Forhandl., Bd. v., p. 691 
 (VircJiow-Hirsch, Jahretber., Bd. i., p. 314, 1870). 
 
 Lambl, " Cercomonas et Echinococcus in hepate hominis," Rutsian Medical Report, 
 No. 33, 1875 (Russian). 
 
 Zunker, " Ueber das Vorkommen der Cercomonas intestinalis im Digestionskanal des 
 Menschen und deren Beziehung zu Diarrhoen," DeutscJie Zcitschr. filr praktiscJie Medici*, 
 No. 1, 1878 (proparte). 
 
 [Grassi, " Intorno ad alcuni protisti endoparassitici," Atti. Soc. Ital. sci. not., vol. 
 xxiv., pp. 12-22, 1882. R. L.] 
 
 The body is generally pear-shaped, and bears a rigid terminal fila- 
 ment almost as long as itself, in addition to the much longer and very 
 delicate vibrating u'hip-shaped flagellum. 
 
 As I have already said, Cercomonas intestinalis is known " with 
 tolerable accuracy," and this is due to the descriptions of Davaine, 
 whose observations, although the oldest on the subject, are still the 
 
 FIG. 121. Cercomonas intestinalis. A, larger, and B, smaller variety. 
 (After Davaine. ) 
 
 most exact and best we possess (Fig. 121). Yet even Davaine distin- 
 guishes two varieties of these forms, differing from each other in form 
 
OCCURRENCE IN VARIOUS DISEASES. "243 
 
 and size, and perhaps even in the structure of the flagellate apparatus, 
 so that one of them (the smaller variety) is almost nearer to the genus 
 Amphimonas, Duj.=odo, Ehrbg. 
 
 The larger variety, whose length varies from O'Ol to 0*012 mm., 
 was very frequently found in the stools of patients during the cholera 
 epidemic, and often in such numbers that a single drop would con- 
 tain several of them. The body was pear-shaped, and had in front a 
 longish structure (" trait longitudinal "), which appeared almost like a 
 mouth. A nucleus could hardly be distinctly seen. The little 
 animals generally moved with great speed, but often attached them- 
 selves firmly to foreign bodies by means of their terminal filaments, 
 and then exhibited a pendulous swinging instead of a progressive 
 motion. 
 
 The second small variety, which was only once observed in a 
 case of typhus but on this occasion in great numbers had a rounder 
 body (0*008 mm.) and two flagella of indefinite length, one in front 
 and one behind, but both situated somewhat to the side. The motion 
 is described as extremely rapid. 
 
 It is still, however, a moot-point whether these two varieties are 
 really different. The illustrations which we have reproduced show only 
 slight variations; and the difference in the structure of their appendages, 
 which alone could be of any significance, is so slightly established by 
 Davaine, that for the present no importance can be attached to it. 
 Hence, later observers have classed these two varieties together again 
 without further discussion. They also recognise only a single Cerco- 
 monas intestinalis, namely, "that observed by Davaine." [Grassi 
 (loc. cit.*), too, observed variations in form and size in his Cercomonas 
 (Monadacomonas), but nevertheless speaks of another, which he refers 
 to our Trichomonas intestinalis. E. L.] It is true that a second form, 
 which we shall soon consider, has been noted by other investigators, 
 and especially by Zunker ; but they have made no attempt to identify 
 it with the different varieties of Davaine, but have rather sought to 
 establish its claims as a separate species. 
 
 These later observations have also shown that the occurrence of 
 Cercomonas intestinalis is much more frequent and extensive than the 
 communications of Davaine led one to suppose. Not only is the 
 parasite found in the intestine (or in the excrement) in cases of cholera 
 and typhus, but also in other diarrhcetic conditions, 1 whether these 
 are dependent upon an acute or on a severe chronic disease. Lambl, 
 
 1 Losch holds (loc. cit.) the occurrence of Monads to be quite common in dysenteric 
 stools. [Grassi observed Cercomonas in different parts of Italy more than one hundred 
 times in the course of a few months. Cunningham also alleges that this parasite is ex- 
 ceedingly common in India (especially in alkaline faeces), and is not unfrequently found 
 in quite healthy individuils. "R. L.] 
 
244 
 
 CERCOMONAS IXTESTINALIS. 
 
 who observed these parasites in myriads in the jelly-like intestinal 
 mucus of children as early as 1859, but published then only a very 
 insufficient description of them, 1 mentions afterwards, in the paper 
 cited, a case in which Cercomonas intestinalis (or at least a form which 
 cannot by our present means be distinguished from C. hominis) was 
 found even in the liver. 
 
 The person infested was a patient suffering from Eckinococcus, who 
 died in consequence of the treatment (with caustic paste). On a 
 post mortem examination twelve hours after death a large Echinococcus 
 (32 cm. long, 18 to 20 cm. broad) was disclosed in a cyst, apparently 
 formed from a widened and degenerated bile-duct, and containing a 
 
 FIG. 122. Cercomonas from the liver. (After Lambl.) 
 
 slimy liquid, in which were, besides Vibriwies of diverse sizes, a 
 countless number of living specimens of Cercomonas. This fluid, 
 together with the contents of the bladder-worm, yielded sediment of 
 nearly 500 c.c., in which the animals occurred in such abundance that 
 a large number were to be found in every drop. They generally 
 showed an extremely quick, but very variable motion, and sometimes 
 hung grouped together in dozens around a common centre. 
 
 The size varied exceedingly between the limits of 0'005 and 0'014 
 mm. The form also varied according to the contraction of the body, 
 but was generally elliptical or spindle-shaped, or sometimes rather 
 pear-shaped or cylindrical. Flagellum and terminal filament could be 
 distinctly demonstrated, although the former was extremely fine, and 
 although instances occurred in which both appeared to be wanting. 
 Lambl, who, it may be remarked, cites his colleagues at Warsaw as wit- 
 
 1 Prager Vierteljahrsschr. f. prakt. Jfeilk., Bd. lxi. f p. 51, 1859 ; Aus dem Franz - 
 Joseph-Kinderspitale in Prag., Bd. i., p. 360. 
 
PATHOLOGICAL SIGNIFICANCE. 245 
 
 nesses of his observation, thought he could distinguish a ventral and 
 dorsal surface in the parasites which he kept alive for a week in their 
 usual liquid. The latter surface has, he says, a firmer parenchyma 
 and smoother contour, while the ventral is softer and more mobile. 
 This appearance of greater mobility arises partly from the play of an 
 opening situated at the base of the flagellum, which obviously repre- 
 sents a mouth, and is surrounded by contractile borders. Besides 
 some strongly refractive granules, two pulsating vacuoles could be 
 distinguished in the hyaline parenchyma posteriorly. 1 A division 
 was also observed, both in the mobile forms and in those which had 
 contracted into a ball, and had lost apparently both flagellum and 
 tail. Finally, the twin forms are connected together only by a thin 
 thread, which has been regarded as the flagellum. 
 
 Even if the reproduction of Cercomonas had not been directly ob- 
 served, yet the consideration of its occurrence in immeasurable num- 
 bers would have necessarily led us to the same result. The possibility 
 of an oft-repeated and sustained importation, which one could perhaps 
 admit when the parasites inhabit the intestine, is here excluded by the 
 facts of the case. Not only because the patient, a gardener, spent the 
 last two months of his life in the hospital, in which such an importa- 
 tion could hardly take place, but, still more cogently, because on post 
 mortem examination the parasites were found exclusively confined 
 to the Echinococcus-s&c, not a trace of them being found in the 
 intestine. We must of course suppose that the Cercomonas had pene- 
 trated into the liver from the intestine, but that had probably taken 
 place a long time before, perhaps at the commencement of the Echino- 
 cocc-^s-disease, which had lasted for five years, according to the patient's 
 report. Perhaps at that time the patient harboured the Cercomonas 
 throughout the whole intestine, and the hepatic parasites, becoming 
 continually more perfectly encapsuled by the JEchinococcus-cyst, are to 
 be regarded as the last survivors of a previous intestinal disease. 
 
 Be this as it may, this much is certain, that the case here cited is 
 not merely the only one of the kind, but has also a special interest in 
 connection with the history of Cercomonas. 
 
 The cases observed by Ekeckrantz, Tham, and Zunker of Cerco- 
 monas in the intestine occurred in individuals who had all suffered 
 
 1 According to Zunker's description, Cercomonas intestinalis has "a longish, oval 
 body, pointed behind, of O'Ol to 0'013 mm. in length ; at the posterior end is a strong 
 spine, and at the anterior a long flagellum, not measurable on account of its constant 
 motion. It has also granules lying in a transparent body, and generally a single vesicular 
 nucleus." A second form, only twice seen by Zunker, along with other intestinal Monads, 
 is compared to the Nonas lens, Ehrbg. It had only a third the dimensions of the 
 common Cercomonas, and a round body, which showed no differentiation, and was in 
 constant motion. 
 
24rt TKICHOMONAS. 
 
 for years from dyspepsia and diarrhoea. The stools were usually 
 peculiar, of a brownish-yellow colour and heavy putrid smell, and 
 generally, in spite of their thin, pulpy consistence, of a toughish 
 character, which probably arose from the presence of numerous masses 
 of mucus. Under these circumstances, the examination of the fsecal 
 masses is sufficient to establish the diagnosis of Cercomonas with 
 tolerable probability, especially since this parasite seems never to 
 occur in the ordinary forms of diarrhoea or in normal stools. 
 
 That the presence of the parasites has a certain connection with 
 intestinal disease cannot be denied, since, according to the unanimous 
 testimony of the investigators, the intensity of the latter is propor- 
 tional to the frequency of the Cercomonas, since an increase in the 
 number of the parasites was always accompanied by an aggravation 
 of the disease, and recovery only took place on their disappearance. 
 
 In spite of this, however, it would be unsafe to refer the intestinal 
 unhealthiness exclusively to parasites. At any rate, a link is still 
 wanting in the chain of proof. Until this is supplied, it seems more 
 probable to suppose that the mucous masses produced by diarrhoetic 
 conditions supply a favourable breeding-place for the parasites (as 
 was similarly noted in the case of the so-called Bodo urinarius), 
 and that they sometimes promote their increase to such an extent 
 that they become a decided irritant, and thus tend to aggravate the 
 disease. 1 
 
 In one case of a patient suffering from Carcinoma ventriculi, 
 Zunker observed this parasite even in the mouth, among the fur 
 covering the tongue, but in the thin pulpy stools only a few speci- 
 mens could be found. 
 
 Trichomonas, Donne. 
 
 The oval body is provided not only ivith a flagdlum, usually double 
 or triple, but also with a longitudinal fringe w % undulating comb. 
 
 The genus, which we have shortly characterised above, was 
 founded on a parasitic Monad, living in the human vaginal mucus. 
 For a time it appeared as if this form (T. vaginalis) was to remain 
 the only one of its kind, until Dujardin discovered a second (T. limacis) 
 in the intestine of the field-slug. Other species were afterwards 
 added to the genus, but all which have been found and described 
 are parasites, and indeed intestinal parasites, so that there are appa- 
 rently no free-living TricJwmonades. We now know that they occur 
 
 1 [Grass! and Cunningham are both disposed to deny any pathogenic significance to the 
 Cercomonas. R. L.] 
 
STRUCTURE OF THE CIL1AKY COMK. 
 
 247 
 
 both in Invertebrata (for example in the rectum of the larva of the 
 cockchafer) and in Vertebrata, both in cold-blooded (Trichomonas 
 batrachorum) and in warm-blooded animals, and especially in mam- 
 mals, as in the stomach of the pig and the intestine of the guinea- 
 pig. Nor is it to be denied that some of the forms in the human 
 intestine described as Cercomonas belong to this genus. 
 
 After the observations which Stein has published concerning 
 Trichomonas batrachorum, 1 some modification must be made in the 
 opinion hitherto held by all investigators in regard to the structure of 
 the lateral comb, so characteristic of this order. For this does not 
 consist of single short filaments in a row near each other, but of an 
 undulating membrane, the vibrations of which easily gave rise to the 
 idea of ciliary motion. Here I may mention the familiar spermatozoa 
 of the salamander, whose fringed edges were also long referred to the 
 possession of cilia. According to Stein, however, the definition of it 
 as an undulating membrane is not perfectly correct. It should rather 
 be said that the extremely soft body rapidly pushes out, one after 
 another, tooth-like or rounded processes, which together produce the 
 impression of a wave ceaselessly running from front to back, along 
 the margin of the body, or " as if this were provided with a toothed 
 undulating membrane." It is not easy to see how this conception 
 can agree with the fact that the apparatus in question also appears 
 
 FIG. 123. Trichomono.8 batrachoram (after Stein). 
 
 in dead animals in the form of an irregularly waving margin, which, 
 as I further note, allows itself to be stained in toto. [This has 
 recently been stated by Blochmann 2 in opposition to Grass! (loc. cit.\ 
 
 1 Lor. ,-!t., j>. 7i. - Zfitschr.f. wigs. Zool., Bd. xl., p. 42, 1884. 
 
248 THICHOMONAS VAGINALIS. 
 
 who regards the ciliary comb as a long flagellum directed backwards, 
 and refuses to recognise the genus Trichomonas. R. L.] On this 
 ground also, I believe that T. batrachorum not merely seems to have, 
 but really has, a vibrating membrane. I am further confirmed in this 
 opinion from the fact of an Infusorian with a ciliated border having 
 been formerly found by Eberth in the Lieberkiihnian glands of 
 the alimentary canal of hens and ducks (Fig. 124), which probably, 
 too, was nothing but a Trichomonas, in which the presence of the 
 flagellum was overlooked. 1 
 
 FIG. 124. Infusorians with undulating longitudinal membrane from the intestine of 
 the hen (after Eberth). 
 
 Since Trichomonas batrachorum is, on account of its considerable 
 size, a much more convenient object than the human Trichomonas, we 
 may assume for the latter the same structure of the accessory ciliated 
 apparatus, although we must leave it to the future to justify this 
 procedure. 2 
 
 Trichomonas vaginalis, Bonne'. 
 
 Donne", " Rech. microscop. sur la nature du mucus :" Paris, 1837. 
 
 Idem, "Cours de microscopic," pp. 157-161, Fig. 33, 1847. 
 
 Kolliker und Scanzoni in Scanzoni's " Beitragen zur Geburtskunde," t. ii., pp. 131-137, 
 tab. in., Fig. 2 : Wiirzburg, 1855. 
 
 Hausmann, "Die Parasiten der weiblichen Geschlechtsorgane, " p. 42 : Berlin, 1870. 
 
 Hennig, " Der Katarrh def hmern weiblichen Sexualorgane," p. 66 : Leipzig, 1870. 
 
 [Blochmann, "Bemerkungen iiber einige Flagellaten," Zeitschr. f. Wise. Zoo/., Bd. xl., 
 p. 42, 1884 (with Fig.)]. 
 
 This form has a somewJiat bulging, oval body, on an average about 
 0'015 mm. long, not including the terminal filament, which is half the 
 length of tJie body. The flagella, which do not exceed the whole body in 
 length, are generally three in number. The lateral undulating comb 
 reaches from tJie anterior margin to about the middle of the body, and 
 
 1 Stein, who expresses the same opinion, blames me for having " immediately " made 
 a separate genus (Sacnolophus) of this parasite (see the first German edition of this work, 
 p. 140). In exculpation, I may state that at that time, when the structure of the acces- 
 sory ciliated apparatus of Trichomonas was still unknown, the Infusorian described by 
 Eberth stood completely isolated, and therefore had to be regarded as the representative 
 of a special genus. 
 
 - [This has been confirmed by Blochmann (loc. cit.). K. L.] 
 
STRUCTURE AND OCCURRENCE. 249 
 
 is said by older observers to consist of six or seven short hairs, which are 
 in constant vibration. The parenchyma is colourless and clear, with 
 fine granules in the interior (Fig. 125). 
 
 As will be seen from the foregoing diagnosis, our knowledge of the 
 vaginal Monads has only reached a satisfactory state in consequence 
 of Blochmann's researches. Even the num- 
 ber of the flagella was uncertain, being 
 supposed to vary from one to three. Where 
 apparently only one is present, they have 
 probably coalesced, as may be guessed from " 
 the fact that in such cases the flagella are 
 sometimes represented as divided at the 
 end. A fine longitudinal line running FIG. i25.Trickomonas 
 
 j ,, .,..., alls. (After Kolliker.) 
 
 down near the accessory cilia is interpreted 
 as the mouth, with what accuracy is a moot-point; it might more 
 probably represent the point of attachment of the ciliary comb. 
 [In the anterior end is a distinct nucleus (Blochmann)]. 
 
 Some investigators assert that they have seen forms of Trichomonas 
 which were in a state of greater or less expansion, and were furnished 
 with stiff, bristly hairs, and have even tried to make a particular species 
 of them. To all appearance, however, these statements deserve but 
 little confidence. These parasites are extremely sensitive to water 
 and watery solutions, and generally perish quickly after the applica- 
 tion of sucli fluids. They then swell up, and coagulate into a more or 
 less globular mass motionless, and robbed of its appendages. As these 
 much altered forms have a certain resemblance to ciliated cells, it is 
 very likely that they were the origin of the above statements, just as 
 in earlier times they gave rise to the very widely spread opinion, held 
 by many weighty authorities (such as Valentin, Siebold, and others), 
 that the Trichomonas of Donne represented only isolated and altered 
 ciliated cells. 
 
 In their natural condition the vaginal Monads show a quick and 
 lively motion, which, when the parasites are present in great numbers, 
 almost gives the impression of the so-called Infusorian "swarming," and 
 especially since the animals frequently crowd round a lump of mucus, 
 or are united into a group by means of their tails. The motion also 
 changes, more or less, as the body turns first right, then left, in con- 
 sequence of the influence exerted on it by the undulations of the 
 ciliary comb. [These forms have also a creeping motion like Euglena.] 
 If the surrounding temperature be reduced, the motion becomes 
 slower, and entirely ceases a few minutes after 9 C. is reached, but 
 recommences as soon as heat is again applied. 
 
250 TRICHOMOXAS INTESTIXALIS. 
 
 Nothing is known regarding the reproductive process, for though 
 Hennig mentions having seen two animals hanging firmly together by 
 their tails, and interprets the process as an act of copulation, it might 
 very probably merely represent the result of division. 
 
 Donne*, who first discovered these parasites in women suffering 
 from gonorrhoea, thought for some time that he could attribute a 
 diagnostic value to them, but afterwards convinced himself that they 
 occurred quite as frequently in uninfected persons. In quite normnl 
 vaginal mucus, containing only separated epithelial cells, but no mucus 
 nor pus corpuscles, the parasites indeed appear to be absent. But in 
 increased secretion, especially of the mouth of the womb and upper 
 part of the vagina, they become quite frequent, and are the more 
 likely to occur when the secretion gives a strongly acid reaction, 
 is of a creamy nature, and rich in pus corpuscles. Kolliker and 
 Scanzoni found these parasites in the majority of persons whom they 
 examined, and during pregnancy as well as at other times. Haus- 
 mann mentions that he found them thirty-seven times in two hundred 
 pregnant women, and forty times in one hundred not pregnant, In 
 the secretion of the cervix, which differs both chemically and histolo- 
 gically from the vaginal mucus, TricJwmonas is never found. 
 
 Trichomonas intestinalis, Leuckart. 
 
 Man-hand, Archiv f. pathol. Ancti., Bd. Ixiv., p. 294 (Uercomoneu intcttinalu), 1875. 
 Zunker, Zeftschr.f. pract. Medicin, No. 1, p. 1, 1878 (pro parte). 
 
 This species resembles the above in size, form, and in the possession 
 of a tail, but is destitute of flagella (?). The ciliary comb is distinctly 
 developed, and seems to consist, as the accompany- 
 ing illmtration shoius, of at least twelve hairs 
 (Fig. 126.) 
 
 I think I am not mistaken in referring 
 to the genus Trichomonas yet another Infu- 
 FIG. 126 1. Trichonwnas in- sorian form, 1 which was first found by 
 
 teslinalis (after Zunker). ,., , , . ,. . . . J 
 
 Marchand in the stools of a typhus patient, 
 
 and afterwards by Zunker in severe intestinal disease, but was looked 
 upon by both as a Cercomonas. It is true that neither of the two 
 observers mentions the flagellum, which must be regarded as a 
 characteristic mark of Trichomonas ; but it is probable that they 
 
 1 Stein wished also (p. 40) to claim the Cercomonas intestinalis, first found by Larnbl 
 in the small intestine of a child, as a Trichomonas, but Lambl himself fterwards estab- 
 lished its identity with the Cercomonas from the ZiWuwotr/w-tuinour, so that it is a 
 genuine Cercomonas. 
 
STRUCTURE AND PATHOLOGICAL SIGNIFICANCE. 251 
 
 merely overlooked the two closely approximated thin threads, as has 
 often been done in similar cases even by skilful investigators. Apart 
 from this, the parasite in question has so striking a resemblance to 
 Tricliomonas vayinalis, that the two forms could hardly be distin- 
 guished, if the accompanying plates did not show the ciliated fringe of 
 Tricliomonas intestinalis consisting of a much larger number of cilia. 
 
 The form of the mobile animal in its condition of rest is, according 
 to Zunker, best compared to a somewhat long almond kernel. It 
 consists of a transparent mass of protoplasm, which contains, 
 besides some irregularly scattered granules, one or two vesicular 
 structures (vacuoles ?) lying in the pointed posterior end of the body. 
 At the posterior end there is also a short spine-like process, while 
 the rounded-off anterior portion seems to exhibit a very distinct row of 
 cilia, which by their rapid action produce a continuous undulating 
 motion. Under favourable circumstances the animals were extremely 
 lively. They moved with great rapidity, and also possessed great 
 contractility, so that the form of the body often changed in an almost 
 amoeboid manner. The dimensions varied from 0*007 to O'Ol mm. in 
 breadth, and from O'Ol to O'Ol 5 mm. in length, exclusive of the long 
 tails, which were from 0'002 to 0'003 mm. long. The nearer the time 
 of death approached, the weaker the motions became. The animals 
 remained upon the same spot, turned round in a circle on the anterior 
 end, or swung like a pendulum, using the caudal extremity as a point 
 of support. Finally, they sank down motionless, lost the ciliary 
 comb, and assumed a round shape, most deceptively like the dull 
 granular clotting of a cell. The rapidity with which death followed 
 depended very essentially on the surrounding temperature, just as we 
 noted before in the cases of Trichomonas vaginalis and Cercomonas 
 intestinalis. 
 
 What has been previously observed as to pathological and clinical 
 significance, and as to the nature of the Monad-containing fceces in the 
 case of Cercomonas intestinalis (which, according to Zunker, seems 
 much more rare than Trichomonas, since he only observed it twice 
 and Trichomonas seven times), is so perfectly applicable to this second 
 .species that 1 shall content myself with referring to it. But this much 
 may be added, that this Trichomonas occurred in acute cases of 
 typhus, peritonitis, and in severe diarrhoea, complicated by icterus and 
 pneumonia, as well as in chronic ailments (which were again generally 
 diarrhoetic). 
 
 In conclusion, I may note that Trichomonas intestinalis, like Cerco- 
 monas intestinalis, is probably sometimes found in the human mouth. 
 I base this supposition on the researches of Steinberg, who, in the 
 above-mentioned treatise on the microscopic character of the dental 
 
252 INFUSORIA CILIATA. 
 
 deposit in men, mentions no fewer than three species of Trichomonas, 
 which are respectively described under the names of T. elongata, 
 T. caudata, and T. flagellata. 
 
 Order II. CILIATA. 
 
 Stein, " Der Organismus der Infusionsthiere : " Abth. i., 1859; Abth. ii., Leipzig, 1867. 
 
 Infusoria with numerous cilia, which are never confined to the 
 immediate neighbourhood of the mouth, but either cover the whole body 
 or are disposed in greater numbers, and in more regular groups on the 
 anterior portion, or on the ventral sarface. The body-parenchyma 
 exhibits, as a rule, a distinct differentiation into a cortical layer and 
 central mass, and usually contains a nucleus and accessory nucleus. 
 When a mouth is present there is also an anus. 
 
 This division contains the larger and more highly developed 
 Infusorians, the properly typical forms with respect to which what 
 we have before remarked in regard to reproduction and multiplication 
 primarily and specially holds good. 
 
 Although agreeing in certain essential conditions, the Ciliata show 
 manifold differences in the details of structure, not only in the above- 
 mentioned ciliary apparatus, but in form and habit, and especially 
 in the mode of motion. Some have attempted to turn these differ- 
 ences to account by dividing the Ciliata 1 again into a number of sub- 
 orders. Thus they distinguish in the first place a group " Holotricha," 
 so called because the generally flattened and oval body is covered 
 throughout its whole extent by a thick coating of short cilia. In the 
 group " Heterotricha " there is, in addition to this covering of cilia, a 
 peculiar modification of the oral region, which develops by flattening or 
 by excavation into a larger and smaller peristome. This peristome is 
 sometimes indicated even in the Holotricha, but in the Heterotricha 
 it is always distinguished by one of its edges being furnished with a 
 longer or shorter, and sometimes spiral, row of strong cilia, which 
 can be traced as far as the mouth aperture. In the so-called 
 " Peritricha " this per'istoniial region surrounds the whole anterior 
 end of the body, which thus possesses a complete girdle of cilia, and 
 can also be retracted to a greater or less extent into the other portion 
 of the body. In individual members of this group an aboral girdle 
 of cilia occurs, in addition to the cilia of the peristoniial region, while 
 the former uniform ciliated coat is completely absent. The body has 
 besides a cylindrical form, so that the structure appears somewhat 
 
 1 The altogether unciliated adult Suetoria, or Acinetans, are not taken into account, 
 as they never appear as parasites in the Vertebrata. 
 
ORGANISATION OF THE C1LIATA. 253 
 
 radiate. Unlike the members of the last group, the so-called 
 " Hypotricha " are bilaterally symmetrical with flattened body and an 
 arched back. The latter is completely naked, for the cilia, which 
 are partly in the shape of stylets and hooks, are developed exclusively 
 on the ventral surface, on which the mouth is also found. With the 
 help of these appendages, the animals exhibit a regular creeping motion. 
 
 All these groups, with the exception of the last, contain, besides 
 free-living forms, parasitic species, which infest both the higher and 
 lower animals. Thus the paunch and reticulum of the sheep and ox 
 harbour no fewer than six different species of ciliated Infusorians, 
 and that in such abundance and constancy, that they are always to 
 be found, along with the above-mentioned Monads, in countless 
 numbers in every individual. Five of these (species of Ophryoscolex 
 and Entodinium) are remarkable mail-clad forms with retractile organs, 
 and belong to the Peritricha ; the sixth (Isotricha intestinalis} is one 
 of the Holotricha. 1 Along with the latter we must include the 
 mouthless genus Opalina, which has, however, been hitherto observed 
 only in cold-blooded animals, but is very often found as constantly 
 and frequently 2 in the cloaca of the Batrachia, and especially of the 
 common frog, as are the formerly mentioned parasites in the ruminants. 
 Along with the Opalince, other heterotrichous parasites are found in 
 the frog, all which forms were referred by Ehrenberg to the great 
 genus Bursaria, but we now know that they belong to certain ex- 
 clusively parasitic groups (Balantidium , Nyctitherus) which are nearly 
 related to Bursaria, and which form along with them the family 
 of the Bursariese. 
 
 To this family, and indeed to the genus Balantidium, we must 
 also refer the so-called Paramcecium coli, the only ciliated Infusorian 
 which has been as yet found in the human body. Other ciliated 
 forms have, it is true, been observed in men, in unclean wounds, 
 ulcers, &c., but always only free-living forms, which generally live on 
 putrefying matter, so that, in spite of their occurrence in this way, 
 they ought hardly to be reckoned among genuine parasites. J. Vogel 
 mentions among these forms Colpoda cucullus and Vorticella, 3 which 
 are both extremely common in putrid infusions. Wedl also mentions 
 a Bursaria (?), 4 but from the "flapping" motions of the lips of the 
 
 1 Regarding these species see the statements of Stein (Lotos, Jahrg. ix., pp. 55, 1859, 
 and Abhandl. der kgl. Bohmischen Gesellsch., Bd. x., p. 69, 1860). In the colon of the 
 horse there very often occurs a hitherto but little known Infusorian, which, so far as 
 regards the nature of its cilia, might belong to the above-mentioned genus, Isotricha, 
 or Balantidium, and at any rate possesses a completely ciliated oval body. 
 
 2 The parasitic Infusoria of the frog were detected even by Leeuwenhoek, " Op. omn., 
 Anat. et Contempl," t. i. p. 56, 1722. 
 
 3 " Pathologische Anatomie," Th. i., p. 404, 1845. 
 
 * " Grundziige der pathol. Histologie," p. 796, Fig. 195. 
 
254 BURSARIES BALANTIIHUM. 
 
 slit-like mouth, I am inclined to think that this species is simply 
 the very common Glaucoma scintillans, Ehrbg. 
 
 Family BURSARIES. 
 
 Heterotrichous Infusoria, with a sometimes oblique, sometimes straight, 
 peristomial cleft, which runs from the anterior end of the egg-shaped 
 body, generally on the right side of the ventral surface, as far as the 
 mouth, and is bordered only on the left side by the adoral cilia. 
 
 Balantidium, Claparede and Lachmann. 
 
 The body is egg-shaped, or rather longer, with ventral and dorsal 
 surface almost equally arched, anteriorly somewhat truncated, and pro- 
 vided with a peristomial region, which narrows posteriorly, and only 
 deviates slightly towards the right side of the ventral middle line. Tliis 
 asymmetrical condition is most striking in a state of rest, when the 
 peristome is bent together into a trough-like shape. The adoral cilia of 
 the left peristomial border differ only slightly in length and strength from 
 the cilia of the body. The mouth occupies the deepest part of the peri- 
 stomial region, and is continued into the interior by a short gullet. The 
 anus at the posterior end of the body is recognisable by the escape of 
 excrement. There arc generally two or three contractile vesicles. The 
 nucleus is of an oval or short ribbon-like form. All the species live 
 parasitically in the alimentary canal of the Vertebrata, especially in the 
 naked Amphibia. 
 
 The genus Balantidium was instituted by Claparede and Lach- 
 mann, 1 for the reception of Ehrenberg's Bursaria entozoon, but was 
 erroneously credited with styliform cilia on both borders of the peri- 
 stomial notch. Stein was the first to recognise the true nature of 
 the peristome, and he increased the number of species, partly by new 
 discoveries, and partly by proving that the so-called Paramcecium coli 
 also belonged to this <zenus. 
 
 Balantidium coli (Malmsten), Stein. 
 
 Malmsteu,'* Archiv. f. pathol. Anat., p. 302, Bd. xii., 1857 (Paramcecium coli). 
 Leuckart, " Parasiten," first German edition, Bd. i., p. 146. 
 Stein, " Organismus der Infusorien," Abth. ii., p. 320. 
 
 Ekeckrantz, Bidrag till kannedomen om de i menniskans tarmkanal forekommande 
 Infusorier," Nord. med. Ari'iv, No. 20, Bd. i., 1869. 
 
 Wising, " Till kannedomen om Balantidium coli hos manniskan," ibid., Bd. iii., No. 3, 1871 . 
 
 Infusoria with a short oval body (of - 07 to O'l mm. long by O'Oo to 
 07 mm. broad); the anterior end somewhat truncated, urith a very short 
 
 1 Etudes, toe. cit. t t. i., p. 247. 
 
HISTORY AND OCCURRENCE. 255 
 
 peristome, which usually extends to the right of the middle line, in the 
 form of a funnel, narrowing to a small cleft, and leading into a short 
 gullet. While feeding the peristome is tooadened out, so as to look like a 
 triangular surface, sloping away obliquely towards the anterior loi^der. 
 
 FIG. 127. Balantidium coli, with widely FIG. 128. Paramcecium (?) coli. 
 
 opened peristome (dorsal view). (After Malmsten). 
 
 The nucleus is elliptical, and slightly lent, two sluggish contractile 
 vacuoles usually lie on the right side, one behind, the other further for- 
 ward. The anus is hardly perceptible. 
 
 Balantidium coli (Fig. 127) was first detected in 1856 by Professor 
 Malmsten, in Stockholm, in the stools of a man who had two years 
 before suffered from a violent attack of cholera, and had since continu- 
 ally complained of dyspepsia, and was alternately affected with consti- 
 pation and with painful diarrhoea. On examination of the rectum there 
 was seen, about an inch above the anus, a small sore, which produced 
 a purulent secretion, mixed with blood ; in this the Infusoria were 
 found in large numbers. Even after the wound healed the former 
 troubles remained, and the Infusoria were still found in the faeces 
 and intestinal mucus. Even at the time of discharge the almost 
 convalescent patient was still infested with the parasites, although 
 their number had considerably decreased. The investigation of the 
 Infusorian was undertaken with the help of the famous zoologist 
 Loven, and it was he who recognised it as new, and referred it 
 (Fig. 128) with some hesitation to Ehrenberg's holotrichous genus 
 Paramcecium. Soon afterwards the parasites were abundantly ob- 
 served in a woman who had suffered for years from a severe in- 
 testinal trouble, and who applied for treatment enfeebled by continual 
 diarrhoea, with bloody and purulent stools. The patient died after a 
 short time. During the last stages of the disease the faeces had been 
 voided involuntarily, and with a fearful stench. Post mortem examina- 
 tion showed numerous small gangrenous ulcers in the large intestine, 
 
256 BALANTIDIUM COLI. 
 
 which was, from the sigmoid flexure onwards, filled with stinking pus. 
 At these places but few Infusoria were found, but they were present 
 in immense numbers over the whole of the sound mucous membrane 
 of large intestine, as also in the atcum and vermiform appendix. 
 There were none to be found either in the small intestine or in the 
 stomach. 
 
 Stein has made it probable that this parasite had perhaps been 
 previously observed, and that by the great discoverer of the Infusoria 
 Leeuwenhoek himself. The latter at least reports 1 that, once 
 having had for a lengthened period abnormal stools, he made an 
 examination of them, and observed delicate mobile organisms, mostly 
 about the size of a blood corpuscle, but some larger, which moved about 
 with the aid of a little foot-like hook. In small portions of the faeces, 
 as large as a grain of sand, there was at least one of these little 
 animals, but generally more four or five, or even eight. These 
 never occurred in the normal excrement. Since the Bulantidia are 
 considerably larger than a blood corpuscle, Leeuwenhoek's description 
 seems but slightly applicable ; but probably the report as to the 
 size was based on a merely subsequent estimate, in which a mis- 
 take might easily be made ; and it is indeed impossible that Leeuwen- 
 hoek, with the optical appliances at his disposal, could have seen the 
 movement of cilia, which he describes, in an Infusorian, as only the 
 size of a blood corpuscle. 
 
 The observations of Malmsten still stood alone when I stated, in 
 the first edition of this work (1863), that man was not the only 
 host of the so-called Paramcucium coli, but, on the contrary, that it 
 also occurred in swine, and was in fact found constantly, and in 
 extraordinary abundance, in the colon and cttcum of these animals. 
 In order to see the parasites, one has only to take a probe and remove 
 some dung or mucus from the rectum. Even with a lens one can 
 distinguish colourless Infusoria moving here and there about the dung. 
 
 Since my results have been corroborated in various parts of Ger- 
 many, in Sweden (by Stein, Ekeckrantz, and Wising), and in Italy 
 (Grassi), we may conclude that the pig is the proper host of Bal- 
 antidium coli, and that man only occasionally derives it from the 
 latter, and under favourable circumstances harbours it for a while. 
 In harmony with this is the fact that the Balantidium in man has an 
 average size of 0'06 to 0*07 mm. (according to Wising), which is a 
 little less than that of the forms found in the pig. 
 
 In the meantime, however, the cases investigated by Malmsten 
 have not remained solitary. Stieda 2 first observed the occurrence of 
 
 1 Loc. cit., Part ii., p. 37. 
 
 2 Arrhirf. patlid, Anat., Bd. xxxv., p. 139, 1865. 
 
STRUCTURE AND MODE OF LIFE. 257 
 
 Balantidium in two cases of typhus in the Dorpat Hospital, and 
 Ekeckrantz, 1 Belfrage, 2 Windbladh, 3 and Wising 4 soon reported four 
 more instances. The number of cases was afterwards doubled by 
 Petersson 5 and Henscheri/ so that apparently Balantidium does not 
 belong to the rarer human parasites. The Balantidia were always 
 found in individuals affected with more or less obstinate diarrhoea, 
 and once in association with numerous ulcers, especially of the caecum, 
 which finally led to the death of the patient (Belfrage's case). In one 
 case Henschen observed a complication with acute stomachic and 
 intestinal catarrh, but this was perhaps an exception. 
 
 It is a striking fact that all the cases of Balantidium coli as yet 
 observed have been confined to a somewhat restricted geographical 
 area. No case of this kind has yet been observed in Germany, 
 England, or France, 7 although the examination of the faeces has been 
 prosecuted at the universities in these countries as well as in Stock- 
 holm, Upsala, and Dorpat, and although the swine are probably, and 
 in Germany certainly, infested with these parasites. The reason of 
 this limited distribution in space can only be sought in local conditions. 
 There must be certain habits of life which determine the occurrence 
 of the parasite, but without more intimate knowledge of the circum- 
 stances we can hardly enter into details. Only this much is clear, 
 that the explanation is to be sought primarily in the relations between 
 men (especially in their food and drink) and the swine, which, in the 
 localities referred to, are probably fattened in the houses. 
 
 Structure and Mode of Life. 
 
 The ease with which we can procure specimens of Balantidium coli 
 from pigs has of course aided the progress of our knowledge of its 
 structure and life-history, so that this is at present, though not indeed 
 perfectly complete, at least satisfactory. 
 
 The Body exhibits great permanency of form greater at least 
 than we are wont to find in the naked Infusoria. This is specially 
 true of those specimens which are distended with food, and easily 
 detected by their compressed oval form and rounded posterior ex- 
 
 1 Loc cit. 
 
 2 " Fall af Balantidium coli," Upsala lakareforen. Forhandl., Bd. v., p. 180. 
 
 3 " Fall af Balantidium coli," ibid., Bd. v., p. 619. 
 * Loc. tit. 
 
 5 Upsala Idkareforen Forhandl., Bd. viii., p. 251, 1873 (three cases). 
 
 " Fran Dr. Waldenstroms Poliklinik," ibid., Bd. iv., 591 (one case) ; and " Fern nya 
 Fall af Balantidium coli," ibid., Bd. x., p. 123 (five cases). 
 
 7 [Grassi states (loc. cit., p. 67) that Dr. Graziadi found Balantidium in one of the 
 chlorotic patients at the St. Gotthard Tunnel ; and Treitte also reports it from Cochin - 
 China (Arcldv. med., t. xi., pp. 129-133, 1877). R. L.] 
 
 R 
 
258 BALANTIDIUM COLI. 
 
 tremity. But even the more slender specimens exhibit on the whole 
 but slight contractility, and are never specially lively. The most 
 striking movement one sees is that of the peristome and anterior end 
 of the body, which sometimes stretches out like a neck/ and bends 
 round towards the somewhat less convex ventral surface. 
 
 This is correlated with the nature of the body, which has its inner 
 parenchymatous substance packed full of food, leaving only the front 
 part of the body unoccupied, and reducing the cortical layer to a com- 
 paratively thin sheath. It is, however, well defined, since the two 
 masses differ widely in nature and appearance, and are sharply dis- 
 tinguished from one another. 
 
 TJie Interior Mass consists of a substance finely granular through- 
 out, in which one can distinguish fat granules of varying size, and, 
 especially in the posterior half, one or two larger granular bodies 
 (faecal masses?). Occasionally, too, one sees a starch granule, 
 especially when the pigs are feeding copiously on potatoes. Wising 
 has also observed red and white blood corpuscles (pus corpuscles ?) in 
 the interior of the Balantidia infesting the human intestine. Since, 
 on the whole, but few firm and definite bodies are found in these 
 animals, we may perhaps conclude that their food consists mostly (as 
 in the other species of Balantidiwn) of the more pulpy contents of 
 the intestine. In contrast to the thick interior substance, the cortical 
 layer consists of a clear, almost transparent, protoplasm, exhibiting that 
 striated appearance which often occurs, and more conspicuously than 
 in the present case, among the Infusoria. The striae all start from the 
 peristomial region, and run in long spiral lines to the posterior ex- 
 tremity. They are most distinct in front, and in their arrangement 
 present an almost radiate appearance. They consist probably of fine 
 fibres, which are embedded in the cortical layer at equal distances 
 from one another, and which squeeze the looser parenchyma between 
 them into frills. At the anterior end of the body one can often see 
 these frills in profile as little marginal knobs. On its surface the 
 cortical layer bears a somewhat firm cuticle with cilia, which are, as 
 Malmsten pointed out, more thickly arranged between the above- 
 mentioned frills. 
 
 Observers are not altogether consistent in their descriptions and 
 representations of the peristome. Previously to Stein's researches it 
 was usually regarded as the mouth opening, and is so still by some 
 (Ekeckrantz). This idea is tenable so long as one examines it only 
 in its short and rudimentary state, but not when one compares it with 
 the more developed peristome of other species. This comparison 
 leaves hardly any doubt as to the fact that this structure forms part 
 of the outer body-wall, a part, moreover, easily distinguishable from 
 
STRUCTURE OF THE BODY. 259 
 
 the rest of the surface of the body, but leading so gradually into the 
 mouth that it seems to represent only a sort of pre-oral cavity. 
 
 The Peristome (Fig. 130), as seen in these constantly rotating 
 animals, usually appears as a conical shell, with a slit running up 
 its whole length, opening to the exterior at the right side of the 
 anterior pole, and thence extending obliquely towards the median 
 plane. The narrowed posterior end is continued further into a 
 short gullet, which is never absent (as Stein alleges), but can be 
 followed plainly to the anterior limit of the medullary substance, into 
 which it distinctly sinks. The more or less widely gaping slit of the 
 peristomial funnel, whose left border is beset by the adoral cilia, 
 belongs to the ventral surface. 
 
 These conditions are entirely altered when one has the opportunity 
 of observing the animal feeding. In this act the peristome (Fig. 127) 
 broadens out by the unfolding of its lateral borders into a triangular 
 space, which is recognisable as the anterior portion of the ventral 
 surface obliquely truncated in a dorsal direction. The space is, more- 
 over, almost symmetrical, 1 which shows that the left peristomial 
 border exceeds the right in length and mobility, and therefore projects 
 further out when the funnel is unfolded. The surface is by no means 
 perfectly even, but sinks in posteriorly, so that it passes without any 
 well defined boundary line into the above-mentioned gullet. One 
 sometimes sees these animals creeping on their expanded peristome, 
 as snails do on their foot, without in any way changing the position 
 of the body. The adoral cilia keep up a lively motion, which some- 
 times looks like the rapid rotation of a wheel. The other cilia round 
 the border are stronger and longer than those of the general body 
 surface. On the other hand, the peristomial region itself is (according 
 to Stein) destitute of cilia. 
 
 Besides the gullet (oesophagus) which runs obliquely through the 
 cortical layer, we find internally a nucleus and contractile vacuoles, 
 both of which, of course, belong to the ectosarc. 
 
 The Nucleus lies on the ventral surface, above the middle line, 
 sometimes far forward, sometimes posteriorly. It is only faintly 
 defined, pale, and homogeneous, extended, and not straight, but kidney- 
 shaped. The median constriction, which Loven and Wising thought 
 they perceived, does not in reality exist. Nor have I been able to 
 find a nucleolus, although Wising reports having several times ob- 
 served it as a small round body beside the nucleus. Stein also has 
 looked for it in vain. 
 
 1 Deceived by such appearances, I have, in the first edition of this work, credited the 
 so-called Paramcecium coli with a terminal mouth, and have suggested its association with 
 the genus HolopJirya, if, indeed, it were not preferable to erect it into a new genus. 
 
260 BALANTID1UM COLI. 
 
 The Vacuoles are usually two. One lies at the posterior extremity 
 of the body, the other, separated from it by a varying distance, 
 is further forward on the ventral surface. Sometimes a third is 
 seen, and there are also cases in which only one is present 
 usually the posterior, which is generally the larger. Their state of 
 tension varies exceedingly, and they become sometimes so full that 
 the surrounding substance is protruded like a hump, or the whole 
 body is deformed. The contractions are exceedingly slow and weak, 
 so that they easily escape observation. One sometimes sees the 
 
 FIG. 129. Balantidium cell in conjugation (after Wising). 
 
 vacuoles perceptibly changing their position, and wandering from one 
 place to another. Stein observed them connected by a lacuna, and 
 the contents of the anterior one being conveyed to the posterior. An 
 opening to the exterior has not been observed. 
 
 The Reproduction of Balantidium coli exhibits, according to Wising, 
 a process of conjugation (Fig. 129), in which the peristomial regions 
 are closely fused with one another, while the bodies remain quite 
 separate. The conjugating individuals present exactly the same 
 appearance as Stein described in Balantidium entozoon, except that 
 the changes of the nucleus and nucleolus, which occur normally in 
 the latter, have not been observed by Wising. Indeed, only a few 
 instances of conjugation have been observed, but quite enough to 
 convert the d, priori probable occurrence of the process into a certainty. 
 
 Division is much easier to observe than conjugation. It is trans- 
 verse division which takes place here, as in the allied species, and 
 indeed in the majority of the Infusoria. Stein, Ekeckrantz, and 
 Wising have often observed it, and I have frequently noted it in my 
 later investigations. As regards some points of detail, I am forced to 
 differ somewhat from my predecessors. They describe the body of 
 Balantidium as simply constricting itself in the middle, after previ- 
 ous growth in length, and then, along with the nucleus, separating into 
 
PROCESS OF DIVISION. 261 
 
 two parts, of which the posterior subsequently forms for itself a peri- 
 stome and an adoral zone of cilia. My observation was somewhat 
 different, and agrees with Stein's account of the division of Balanlidium 
 entozoon. The first step in the division of the almost cylmdrically 
 extended body (0*15 mm.) is the formation of a ciliated circle, which 
 surrounds the middle of the body, and comes short of the adoral cilia 
 neither in size nor in lively motion. On the dorsal surface this girdle 
 exhibits a considerable blank ; it is therefore primarily and especially 
 on the ventral surface that it originates, whether by new formation or 
 by outgrowth of former hairs I must leave undetermined. The two 
 vacuoles are widely separated, and the nucleus has grown com- 
 paratively little. 
 
 FIG. 130. Balantidium colivn. various stages of division. 
 
 The girdle of cilia is nothing but the first outline of the subse- 
 quent adoral zone, as the further course of the process shows. One 
 can very easily recognise, close beside the girdle of cilia, a constric- 
 tion which is at first shallow and easily overlooked, but which, after 
 a short time, separates the two halves from one another, so that the 
 connecting part is restricted to a small band. The two halves are 
 easily recognisable as independent organisms, the more so since the 
 granular inner substance is drawn back, especially posteriorly from 
 the line of constriction. The arch of cilia has gathered more and 
 more closely round the anterior pole of the posterior half, and has been 
 continued inwards into a short, flat, but already triangular protube- 
 rance, formed close behind the extremity on the ventral surface. At 
 this stage, the nucleus has usually divided into two parts, which lie 
 one in each half, and are extremely like one another, especially since 
 a second contractile vacuole has made its appearance. As the divi- 
 sion progresses, the posterior peristomial region gradually acquires 
 its more definitive structure, by the growth of the aforesaid protube- 
 
262 BALANTIDIUM COLL 
 
 ranee, and the large cilia sink deeper into it, but finally persist in their 
 former size only on the left margin. Sometimes one finds animals 
 which are all but separate, being united only by a thin connecting 
 thread. In one case in which I observed the separation, I saw this 
 thread draw itself together into a ball, which remained connected 
 with the anterior individual, and looked just like a little ball of dung 
 which the animal was about to drop. These adherent balls are often 
 seen in Balantidium, and have been quite generally described by 
 previous investigators as dung-balls. That this is a mistake I have 
 little doubt, not only because of the previous observation, but because 
 of the fact that it is always the smaller and more slender forms with 
 narrowed posterior extremity that bear this appendage. The size of 
 this ball varies greatly, and is in some cases so considerable that 
 Ekeckrantz regarded it as a bud, and was thereby led to the con- 
 clusion that these Infusorians also reproduced by budding. Although 
 I have actually observed a small vacuole inside one of these balls, 
 I am far from being inclined to interpret this occurrence according 
 to Ekeckrantz's theory. The fact that budding occurs in but few 
 groups of Infusoria, and has never yet been observed in forms allied 
 to Balantidium, is of some weight in this connection. The same 
 may be said in regard to the statement that it is the posterior end of 
 the body which buds, for, a terminal budding is, as far as we know, in 
 the highest degree improbable among the Infusoria. 
 
 Division occurs, to all appearance, so frequently and rapidly 
 among the Infusoria, that we can easily conceive how the number of 
 parasitic inmates, after a time, considerably increases, and after a 
 lengthened period becomes quite immeasurable. The parasitism itself 
 cannot, of course, be thus explained. 
 
 The Mode of Infection by this parasite is at present in a state of 
 uncertainty, and a decided proof is needed as to the form in which 
 the Balantidium gains admission to its host, and until this is furnished 
 our knowledge of the subject cannot claim to be satisfactory. 
 
 So far as we can judge from the analogy of other intestinal In- 
 fusoria, and especially from the facts lately established by Engelmann T 
 and Zeller 2 as to Opalina, we may on d priori grounds expect that this 
 transmission occurs in the encapsuled state, and therefore under cir- 
 cumstances which allow to the Infusorians a further distribution out- 
 side the living organism. And, as a matter of fact, it has been proved 
 beyond a doubt that Balantidium has such an encapsuled state. Even 
 in the first edition of this work I was able to state the results of some 
 observations of this point, which were afterwards confirmed by Stein. 3 
 
 1 Morphol. Jahrb., Bd. i., p. 573, 1876. 3 Zeilschr. f. wss. Zod., Bd. xxix., p. 352, 1877. 
 
 8 Against this corroboration the negative results of Wising's observations have not 
 
 much weight. Besides, Wising does not dispute the correctness of our statements, but 
 
MODE OF INFECTION. 263 
 
 I may premise that Balantidium is by no means so sensitive to 
 the influences of water and cold as the intestinal Monads. Even 
 after copious application of water, we can, without using a warm 
 stage, see the Infusorians moving for a long time without apparent 
 diminution of vigour. But later the animals become wearied, they 
 remain lying on the object glass, and finally suspend the play of 
 their cilia. But even in this state they retain unchanged for hours 
 a fresh appearance. One does indeed find some specimens which 
 are already more or less strongly contracted, and have lost all their 
 covering of cilia, except a few adoral ones. The granular interior 
 mass has gathered together into a heap, from which some large drops of 
 fat shine out. Later still, the cilia and the epistome have disappeared, 
 and the body finally appears as a ball (0*08 to O'l mm.), which is 
 surrounded on all sides by a capsule-like thickened cuticle, but still 
 encloses as before a clearer peripheral layer and a dark central mass 
 with fat-drops. The origin of the -cyst admits of no doubt, for one 
 can often observe in its earlier stages the nucleus and the vacuoles of 
 Balantidium. Since this capsule is found in the deposited and even 
 somewhat dry excrement, one may perhaps conclude that its forma- 
 tion as above described is an entirely normal process, occurring perhaps 
 in all, and at least in many of the parasites expelled with the excre- 
 ment. That the Balantidium-c&psulQ plays an important part in the 
 preservation and transference of these animals, is not only in itself 
 most probable, but finds justification and confirmation in the facts 
 known regarding Opalina. One may indeed doubt whether it is these 
 encysted Balantidia exclusively which bring about the infection, or 
 whether the newly voided animals are not sometimes directly trans- 
 ferred to the intestine, there again to become its denizens. So far as 
 man is concerned, this question is indeed irrelevant, seeing it could 
 hardly happen that he thus infected himself. But it is quite the 
 reverse with swine, which, with their dung-eating habits, might easily 
 afford opportunity for such a mode of infection. 
 
 In support of the position that an effective transmission is only 
 brought about by means of the encysted animals, I lay but little 
 emphasis on the fact that the attempts of Ekeckrantz and Wising to 
 infect dogs and other mammals ( per os et per anum) with dung con- 
 taining Balantidium, have all yielded only a negative result ; but I rely 
 rather on the well-known fact that small delicate skinned Entozoa, as 
 these forms undoubtedly are, cannot without a protective covering 
 survive in the stomach of an animal (p. 76). And it is through the 
 
 thinks that one must not transfer the results of the observation of the Balantidium in 
 swine to that found in man, and sees in this a further reason for not regarding man as the 
 proper and natural host of this parasite. 
 
264 BALANTID1UM COLl. 
 
 stomach that the Balantidia must reach their destined habitation, for 
 an entrance per anum is by the nature of the case impossible. 
 
 Man becomes infected with Balantidium by eating substances with 
 which the encapsuled animals have come into contact ; how this con- 
 tact occurs we can hardly tell, it is simply the result of the same 
 countless chances which determine the ubiquitous distribution of eggs 
 of Helminths. Then, of course, the Balantidivm-cysts are not 
 imprisoned within the pig's dung, but if this be broken and dried up, 
 they may be spread about without loss of the power of development, 
 and may be conveyed to man with an ease proportionate to the 
 closeness of the local relations obtaining between him and the swine. 
 
 As to the pathological import of Balantidium, we might answer 
 much in the same words as in regard to the related Infusoria, the in- 
 testinal Monads, and the Amaebce. It is uncertain whether they 
 can be regarded as having actually a power of originating disease. 
 Although they seem to be constant in pigs, no pathological pheno- 
 mena result. Of course this is not decisive, for we know hrw differ- 
 ent organisms are very variously affected by different influences ; and 
 it is perhaps worth noting, in connection with the above facts, that 
 the excrement of pigs has usually a loose and stinking character, 
 which is not normally the case in man. 
 
 But granted that we cannot directly affirm that the parasitism of 
 Balantidium determines of itself a pathological state, it does not in 
 the least follow that its presence is indifferent to its host. Bather it 
 is, d priori, very probable that the movements of the animals, present 
 as they are in thousands and hundreds of thousands, occasion a state 
 of irritation which might easily increase and aggravate an existing 
 disease. For this reason it is advisable, when the occurrence of this 
 parasite has been proved, to take measures against it, as well as 
 against any other disease. 1 
 
 It is doubtful whether these parasites can live in a perfectly 
 healthy intestine. Hitherto they have been found only in stools of 
 patients otherwise diseased. If these changes be not regarded as 
 a consequence of the parasitism, then evidently one must conclude 
 that an abundant secretion of mucus (for the stools of infested persons 
 are usually pulpy and diarrhcetic) is a condition favourable to the 
 existence and reproduction of Balantidium, as, indeed, we have 
 formerly concluded of the other intestinal Infusoria. But, on the 
 other hand, it is doubtful whether we are warranted in ranking Bal- 
 antidium among the so-called " putrefactive Infusoria," since they live 
 more upon the fluid chyle than upon the secretions of the intestine. 
 
 1 As to the means to be used (clysters of acetic and tannic acids), see especially the 
 reports of Henschel's experiments (loc. cit.). 
 
VERMES. 265 
 
 SUB-KINGDOM II VEBMES. 
 
 Bilaterally symmetrical animals without a skeleton, having a longer 
 or shorter cylindrical or flattened body, which is either perfectly simple 
 or exhibits a larger or smaller number of flat or ring-shaped segments, 
 which thus give their possessors a certain resemblance to the Arthropod a. 
 Dorsal and ventral surface often closely resemble one another. External 
 appendages are in many cases completely wanting. When present, they 
 consist either of organs of attachment (suckers, chitinous hooks, &c.\ or, 
 as in the majority of the segmented or ringed worms, of tufts of bristles, 
 which are then distributed very regularly over the segments. Sometimes 
 branchiae are also found ; if they be not present, the respiration is simply 
 cutaneous. The habitat is in water or in damp localities; the motion 
 is in general slow. 
 
 The animals now included under the designation Vermes form a 
 group much more restricted than was originally intended by Linne in 
 his famous " Systema Natime." The latter included under that name 
 all the invertebrate animals, with the exception of the so-called 
 Arthropods (Insecta, L.) that is to say, a host of animals of the most 
 heterogeneous types, which Cuvier first taught us to distinguish. 
 Worms now include only a small group of these animals, namely, those 
 which remain after the exclusion of the Protozoa, Radiata, and Mollusca. 
 
 To fix the natural limits and characteristics of this division is a 
 very difficult problem of systematic zoology, especially difficult be- 
 cause the worms, even as now limited, represent no uniform group. 
 For our present purpose it is sufficient to describe them as above. 
 
 In regard to internal organization, the worms exhibit almost greater 
 contrasts than in external structure, for there is no single organ which 
 is even essentially the same throughout. Not only is the body-cavity 
 frequently wanting, so that the intestine and the cortical layer, other- 
 wise separated by it, are united into a common mass, but in many 
 cases neither blood nor blood-vessels are present. There are even 
 a great many worms, and particularly among those which we are 
 about to consider, which are entirely destitute of an alimentary canal, 
 although this is by far the most constant of all animal organs, and 
 is hardly ever wanting in the other Metazoa, The disposition of 
 the muscular and nervous systems also exhibits numerous and im- 
 portant differences, which are partly co-ordinated with the external 
 structure of the body. The only organ constantly present is an 
 
266 VERMES. 
 
 anterior so-called cephalic ganglion or brain, from which the nerves 
 radiate anteriorly and posteriorly. In the segmented forms the 
 branches running back are united into a single ventral cord, which 
 forms a special nerve ganglion in each segment. The sexual organs 
 exhibit, in the flat-worms at least, a very considerable development. 
 They consist of male and female parts, which are sometimes in 
 separate individuals, but are also often, and perhaps more frequently, 
 united in the same body. 
 
 The development is as a rule associated with a metamorphosis. 
 In many groups there is an alternation of generations. Thus we dis- 
 tinguish the so-called " nurses," which arise directly from the eggs, 
 and the "sexual animals," which originate partly by budding, and 
 partly from egg-like cells in the interior of the " nurses." 
 
 Of all the divisions of the animal kingdom, that formed by the 
 worms is by far the most important for our present purpose, for to it 
 belong the great majority of parasites, and these the most dangerous. 
 
 In man the parasitic worms inhabit exclusively the internal 
 organs, where they are soaked by the juices of their host. Only on 
 aquatic animals do we find them as external parasites. Their ecto- 
 parasitism on land animals is rendered impossible by the necessary 
 conditions of respiration (see p. 13). 
 
 The parasitic worms infesting man and the higher animals are 
 therefore literally intestinal worms (Entozoa). They have a true 
 right to this name, which is often used in a wider sense to denote all 
 parasitic worms, including even ectoparasites. 
 
 At one time these worms were regarded as forming a single united 
 group, not only with a biological, but also with a systematic signifi- 
 cance ; in other words, they were erected into a special class of 
 Entozoa or Helminths. So is it according to Cuvier, for example, and 
 also according to many more modern zoologists e.g., Owen, v. Siebold, 
 van der Hoeven, &c. Cuvier even had the idea of separating this 
 class of Entozoa from the worms proper (i.e., from the ringed worms 
 (Annelida), which he had united with the likewise ringed Arthropoda 
 into a single group, Annulata), and thought of uniting them with 
 the Eadiata. 
 
 Now, however, zoologists are of a different opinion on this point. 
 Not only do they insist on the union of the Helminths with the 
 higher worms, but deny the propriety of a special class of intestinal 
 worms in any natural system of the animal kingdom. 
 
 Even the adherents of the older opinion must at any rate confess 
 that the aforesaid class " includes most diverse animals " so diverse, 
 indeed, that no common character in their organization is to be found. 
 In reality the limits of the class are simply those of a common mode 
 
SUBDIVISIONS OF PARASITIC WORMS. 267 
 
 of life, a characteristic very important from a biological point of 
 view, but only of subordinate importance in determining natural 
 relationship. To base a classification on such physiological characters 
 is in this case all the more illegitimate, since we know that not a few 
 Helminths live for a longer or shorter part of their life in freedom. 
 
 Also, the older zoologists have never scrupled to refer certain non- 
 parasitic forms, such as the Rlidbditis (Anguillula), to this group, 
 and to refer other really parasitic worms, such as Chcetogaster, 
 Hirudo, &c., to their place beside the true worms. 
 
 When we further recall how many Helminths have an undeniable 
 relationship with free-living worms how the Trematodes, for ex- 
 ample, are, as we have seen (p. 105), closely allied to the Turbellaria 
 how the leech comes almost as a connecting link between the 
 Helminths and the higher worms we shall be sufficiently convinced 
 of the truth of the opinion staunchly upheld half a century ago by my 
 uncle, F. S. Leuckart x namely, that a class of Helminths has only 
 the rank and import of a faunistic group, and ought never to be in- 
 vested with a systematic unity. 
 
 Since the time of Zeder and Kudolphi five distinct groups of 
 Helminths have been generally recognised, whether unified into a 
 special class or no viz., the thread-worms or Nematodes, the Acan- 
 thocephali, the flukes or Trematodes, the tape- worms or Cestodes, and 
 the bladder-worms or Cystici. The attempt of Diesing to form a sixth 
 order Acanthotheci of the so-called Pentostomata has only found 
 a limited support, and calls for no further notice, since we are de- 
 cidedly convinced (p. 14) that these animals, in spite of a certain 
 superficial resemblance to Helminths, have no more claim to be classed 
 as worms than have the Lern?eadcie (p. 92), which were referred to the 
 same class before v. Nordmann's investigations. Just as the latter 
 are Crustacea, as their larval stages indisputably prove, so are the 
 former to be regarded as peculiarly modified mites. 
 
 Nor has it been possible for the five orders of Rudolph! to remain 
 unaltered, for experimental helminthology has established beyond 
 doubt the opinion of Dujardin, v. Siebold, van Beneden, and others, 
 that the bladder-worms were no independent species, but only stages 
 in the development of Cestodes. The order has thus vanished from 
 systematic zoology, and the number of groups of Helminths is thus 
 reduced to four, which have, according to all results, a reasonable 
 claim to be regarded as natural divisions. 
 
 On closer inspection, however, it soon appears that they are not 
 equally closely united to one another. As we formerly showed 
 
 1 " Versuch einer naturgemassen Eintheilung der Helminthen, nebst dem Entwurfe 
 einer Verwandschafts- und Stufenfolge der Thiere uberhaupt :" Heidelberg, 1827. 
 
268 VERMES. 
 
 (pp. 105-109), the Cestodes are closely united to the Trematodes, and 
 the Acanthocephali to the Nematodes ; and this is not only a super- 
 ficial resemblance, but concerns the development and the anatomical 
 arrangement of the intestinal organs. In certain cases the resemblance 
 is so great that it is difficult to determine with certainty the syste- 
 matic position of the animal. Thus we know of Helminths which 
 seem intermediate types between Cestodes and Trematodes such as 
 Ampliiptyches and AmphUiiie. The connecting links between Ne- 
 matoda and Acanthocephali, though not so perfect, are not wholly 
 wanting (Gordius). 
 
 Thus we can distinguisli two great groups of Helminths which 
 have been named according to their most conspicuous external 
 characteristic respectively Playthelminthes (Platyhelmia) and Nema- 
 thelminthes (Nemathelmia). 
 
 We must not, however, forget that these two groups do not repre- 
 sent definite unities, any more than do the Entozoa or Helminths. 
 The intestinal worms have originated, as we have shown (p. 89 et seq.\ 
 by the adaptation of originally free-living forms to a parasitic environ- 
 ment, and both groups are in various ways connected with free-living 
 relatives. The natural system has attempted to express this relation 
 by associating the Platyhelminthes with the Turbellaria and Hirudinea, 
 and Nemathelminthes with the other free-living worms ; in other 
 words, by distinguishing two classes of worms, which include both 
 free and parasitic species, and which are not unfitly distinguished by 
 their characteristic forms as flat-worms (Platodes) and round-worms 
 (Annelides). I will indeed grant that there may be a difference of 
 opinion as to the limits, and even justifiability, of these two classes. 
 This is especially so in regard to the second class, which includes 
 forms widely differing from one another besides the Nemathelminthes 
 and Chcetognatki (Sagitta), also the Gephyrea and Ckcetopoda. The 
 position of the Hirudinea among the flat-worms has also become 
 doubtful (p. 107). 
 
 But all these are questions of subordinate importance for us here. 
 We have to discuss not the systematic position of worms, but their 
 structure and life-history. The above remarks will serve as a general 
 introduction as to the relations of these form?. 
 
PLATODES. 269 
 
 CLASS I. PLATODES. 
 
 Schneider, " Untersuchungen liber Plathelminthen," Vierzehnter Bcricht der oberhess 
 Gesdlsch. Jiir Natur- u. Heilkunde : Giessen, 1873. 
 
 Minot, "Studien an Turbellarien, Beitrage zur Kentniss der Plathelminthen," 
 Arbeiten des zool.-zoot. Institutes in Wiirzburg, Bd. iii., 1876-77. 
 
 Animals with a more or less flat and short body, seldom ringed, 
 either with no appendages, or with organs of attachment in the form of 
 suckers and hooks, varying in number and arrangement. In a few 
 cases there are gills. Generally hermaphrodite, the young forms some- 
 times resemble the adults, but sometimes differ from them, and exhibit an 
 alternation of generations before attaining sexual maturity. When 
 this takes place by budding, the sexual animals remain for a long time 
 united with their nurse in a polymorphic colony. 
 
 The majority are temporary or stationary parasites, as the frequent 
 occurrence of fixing organs would lead one to suppose. 
 
 The alimentary canal has a fleshy pharynx, discharging the 
 function of an organ of attachment or of capture, and showing, in 
 accordance with the form of the body, a striking tendency to rami- 
 fication. In many cases the anus is absent, in others (endopara- 
 sites) even the whole canal, so that the ingestion of food takes 
 place by the surface of the body. Blood and blood-vessels are only 
 found in segmented flat-worms. They have indeed been described also 
 in other forms, but this was due to a confusion with an often rami- 
 fying excretory apparatus which generally occurs in these organisms. 
 The nervous system consists of a ganglion lying in front of the mouth- 
 opening, or at the anterior end of the body, and of nerves running 
 from this, usually with two specially strong and well developed 
 lateral branches. In the segmented flat-worms these unite in the 
 middle line, and form a single chain of ganglia running below 
 the alimentary canal. The sense organs are usually but slightly 
 developed, and in the endoparasites are generally present only as 
 tactile organs. 
 
 A body-cavity, usually present to contain the vegetative organs, 
 is here wanting. These animals are parenchymatous worms (vers 
 parenchymateux), i.e., organisms whose viscera are in continuity with 
 the other tissues, and are directly embedded in the general connective, 
 tissue substance of the body like the muscles and nerves. In other 
 words, the splitting which usually separates the mesoderm into an 
 outer somatic and an inner splanchnic layer has not taken place, or if, 
 
270 CHARACTERS OF THE PLATODES. 
 
 as in the Hirudinea, it has existed for a time, it has been obliterated 
 in the course of further development. Under such circumstances 
 the musculature of the viscera only rarely acquires any inde- 
 pendence, and is generally closely connected with the musculature of 
 the body. However, this is not equally true, as we shall presently 
 see, for all Platodes. Nor is the disappearance of the body-cavity 
 always quite complete, for some of the higher, and even some of the 
 lower (parasitic) forms show evident traces of this structure. 
 
 ORDER I. CESTODA. 
 
 Van Beneden, " Les vers Cestodes ou Acotyles," Mm. Acad. roy. Belg., t. xxv. : 
 Bruxelles, 1850. 
 
 Idem, " M&noire sur les Vers intestinaux," p. 112 : Paris, 1858. 
 
 Flat-worms without mouth or alimentary canal, which typically de- 
 velop by alternation of generations, by budding from a generally pear- 
 shaped nurse, with which they remain united for a lengthened period as 
 a ribbon-like colony or ' strobila" The individual joints of the colony, 
 i.e., the sexual animals or Proglottides, increase in size and maturity as 
 they are removed further from their origin, by the intercalation of new 
 buds, but are not distinguished in any special way. The nurse, how- 
 ever, known by the name of the " head " (Scolex), is provided with four 
 or two suckers, and usually with curved claw-like hooks. The dorsal 
 and ventral surfaces of the head are perfectly identical, so that the ar- 
 rangement of the hooks presents a strikingly, radiate appearance. By 
 means of this apparatus the worms fasten themselves on the intestinal 
 membrane of their hosts, which (except in the case of the otherwise peculiar 
 Archigetes) all belong to the vertebrates. The nurses develop in a more 
 or less complicated fashion as so-called " bladder-worms "from little round 
 six-hooked embryos. The latter inhabit very diverse but usually paren- 
 chymatous organs of the higher and lower animals, and are thence 
 passively transferred to the intestine of their subsequent host. 
 
 What we have here described as a polymorphic colony is that 
 creature which is commonly called a " tape-worm," and regarded as a 
 simple individual with a head and jointed body. At first sight this 
 common conception seems to be perfectly justified, but it can hardly 
 be upheld in face of the facts of the case. It is, for instance, scarcely 
 consistent with our idea of an individual animal to observe that not 
 only can the terminal " ripe " joints of the tape-worm separate them- 
 selves with the greatest facility, and creep about for a while as inde- 
 
CESTODES. 
 
 271 
 
 pendent animals, 1 but the so-called head can, after the loss of its 
 chain of joints, grow again to a new tape- worm within a few weeks. 
 Can we wonder that these observations long ago raised a doubt as to 
 the correctness of the usually accepted theory, and that thoughtful 
 
 FIG. 131. 
 
 FIG. 132. 
 
 Fio. 131. Tape- worm form of Tcenia sayi- 
 nata s. mediocanettata. 
 
 FIG. 132. Isolated Proglottides of the same. 
 
 investigators more than a century ago suggested that the tape-worm 
 was no simple individual, but a compound animal. 
 
 Not to speak of the Arabian physicians, this was the opinion of 
 Vallisnieri 2 and Coulet, 8 and also of Linne, who places the tape- worm 
 
 1 In fact, these discharged joints, especially of Twnia saginata, have been repeatedly 
 considered both in ancient and modern times as distinct parasites, Verities atcurbitini. 
 
 2 " Considerazioni ed esperienze intorno alia generazione dei vermi del corpo umano," 
 p. 75 : Padova, 1710. 
 
 a " Tractatus de ascaridibus et lumbrico lato," p. 37, &c. : Lugd. Bat., 1729. 
 
272 CESTODES. 
 
 in his system beside the polypes among the polyzootic zoophytes, 
 and in other places 1 expressly compares it with a plant of many 
 shoots. 2 
 
 Linnd's conception was also in advance of his contemporaries in 
 this respect, that hitherto they had been inclined to suppose that the 
 tape- worm arose by the isolated joints (Vermcs cucurbitini = chdbb al- 
 kar'i of the Arabians) subsequently forming a chain. And this idea 
 struck its' roots so deeply that even Blumenbach, towards the end of 
 last century, regarded it as correct. Even the unequal development 
 of the individual joints, which surely suggests successive budding, did 
 not lead him to alter his opinion. He tried, indeed, to explain it by 
 assuming that the older worms were ever being sucked out by their 
 progeny, and were thus reduced in size. And yet even at this time 
 the observations of Pallas and others had made it almost indubitable 
 that the smaller joints were the younger, and that they attained the 
 larger size as they gradually grew older. 
 
 The conception of the tape- worm as a polyzootic animal could, how- 
 ever, only slowly gain ground. It appeared as though the presence of a 
 distinct and definitely formed head could not be brought into harmony 
 with it. Pallas, following up Linne, had indeed already attempted to 
 regard this head as the root (quasi-radix) of a plant-like animal, yet, 
 with the exception of Eeimarus, but few zoologists supported his 
 idea. And so it has come about that, in spite of the protests of F. S. 
 Leuckart and Eschricht, the tape- worm has even in our own day, in 
 scientific and popular conception, been persistently regarded as a 
 simple animal. 
 
 It persisted in fact till Steenstrup 3 gave us the key to the proper 
 understanding of the tape-worm, by showing its harmony with his 
 theory of alternation of generations, according to which the head was 
 seen to be the larval " nurse," and the joints the sexually mature in- 
 dividuals. The ingenious Danish naturalist left us, indeed, without a 
 strict proof of the correctness of his theory, but this was speedily fur- 
 nished in such masterly fashion by van Beneden 4 and v. Siebold, 5 that 
 it is now hardly permissible to harbour a doubt as to the compound 
 character of these animals. 
 
 1 " Amcenit. acad.," vol. ii., p. 87 et seq. (Dissert, de t;enia). 
 Qotting. gelehrt. Anzeig., No. 154, 1774. 
 
 3 "Generationswechsel," p. 115: Kopenhagen, 1841; "Alternation of Generations," 
 Ray Society, 1845. 
 
 4 " Les vers cestoides sont-ils mono- ou polyzoiques ?" " Vers Cestoides, ' p. 94, and 
 "M6m. sur les vers intest.," p. 251. 
 
 6 " Ueber den Generationswechsel der Cestoden:" Zeitschr. f.iciss. Zod., Bd. ii.,p. 198, 
 1850. See also his " Abhandlung iiber Band- u. Blasenwurraer," 1854. 
 
SIGNIFICANCE OF THE HEAD. 
 
 273 
 
 As the often corroborated observations of these investigators showed, 
 there is in the developmental history of the Cestodes a stage in 
 which nothing of the future tape- 
 worm is to be seen, except the so- 
 called "head," which then lives by 
 itself like an independent animal, 
 and only gradually and under favour- 
 able conditions buds out one joint 
 after another from its posterior ex- 
 tremity. This isolated tape-worm 
 head, or more correctly " nurse," 
 had indeed been formerly observed, 
 but its true value was not de- 
 tected, and it was usually regarded 
 as the representative of a special 
 form (Scolex, &c.). 
 
 The joints, which are budded 
 off one after the other, are like all 
 buds, at first small and immature, 
 but they gradually increase in size 
 and maturity as they are pushed 
 further from the head by the in- 
 tercalation of new buds. After a 
 certain time, or, what cornes to the 
 same thing, at a certain distance from their nurse, they become sexu- 
 ally mature, sooner in some species than in others. The head, which 
 is usually designated by the originally much more restricted name of 
 " Scolex," remains, like a true nurse, asexual. 
 
 Thus by continued budding there arises from an originally isolated 
 nurse a whole community of individuals a colony, in which one 
 has to distinguish not only animals at various stages of maturity, but 
 also one asexual and aberrant member, the so-called " head." 1 
 
 The significance of this head is not, however, purely genetic. 
 It is not only the origin of the whole chain, but serves further for 
 its fixation, and thus benefits the whole colony. It was formerly be- 
 lieved that nutrition was also effected by the head ; 2 the suckers were 
 regarded as mouth openings (Nitzsch, Owen), or the oral opening was 
 
 1 Van Beneden used the term " strobila " to designate this colony. It was formerly 
 employed by the famous Norwegian zoologist, M. Sars, to denote a stage in the development 
 of certain jelly-fish (Aurelia) a stage, indeed, formerly described by him as a new species. 
 In this instance we have, as in the tape- worm, a "nurse " here in the form of a polype, on 
 which there rises a pillar of young jelly-fish, at first imperfectly separated from one another, 
 but afterwards set free. See Archiv f. Naturgesch., p. 9, tab. i., 1841. 
 
 2 As we shall afterwards see, a similar opinion has lately been advanced by Blumberg. 
 
 S 
 
 Iso- 
 
 ; head" 
 
 of Echineibothrium 
 minimum, van Bene- 
 den, from the intes- FIG. 134. Chain 
 tine of Trygon pas- of joints of Echinei- 
 tinaca. bothrium minimum. 
 
274 
 
 CE8TODBS. 
 
 FIG. 135. 
 
 looked for between the suckers (Bremser, Mehlis), at a point on the 
 top of the head, where the outer coverings are often drawn together 
 into a depression, and where, in some species, a minute but distinct 
 sucker (the frontal sucker) is formed. We know, however, that the 
 Cestodes are wholly destitute of both mouth and alimentary canal. 
 The observation of two repeatedly described longitudinal channels 
 suggested the existence of an alimentary canal, and therefore lent 
 some probability to the above belief in the presence of a mouth, but 
 we shall afterwards see that they are only the main stems of the so- 
 called " excretory vascular " system. 
 
 The physiological significance of the head referred to above is 
 evidently important, since the suspended sexual animals are destitute 
 of hooks. The nurse undertakes the attachment of the colony, and 
 thus has its specific share in the general economy, as is usual in 
 cases of polymorphism. 1 
 
 The association of sexual members (the so-'called " Proglottides ") is 
 
 not, however, a lasting one. Sooner or 
 later the terminal joints become loose, 
 sometimes singly, sometimes in groups, 
 and after remaining for a while in in- 
 dependent freedom beside their still 
 attached fellows, are carried along with 
 the faeces from their intestinal home. 
 As a rule, this separation takes place 
 only after the perfect development of 
 the discharged sexual members, and 
 often, as in Tccnia, after even their 
 embryos are mature; 2 but there are 
 cases where the joints are liberated 
 much earlier. Thus, thanks to van 
 Beneden, we know of certain forms 
 from the alimentary canal of the pre- 
 datory rays and sharks, whose proglot- 
 tides only reach maturity after they 
 have become free, and which, in their 
 isolated state, grow to a size almost as 
 great as that of the whole tape- worm, 
 from which they originated. With 
 such cases before us, every doubt as 
 to the independent nature of the 
 individual joints must vanish. 
 
 1 See Leuckart, " Ueber den Polymorphismus der Individuen oder die Erscheinungen 
 der Arbeitstheilung in der organischen Natur:" Giessen, 1852. 
 
 2 Hence the name " Ovaria amlmlnntia," sometimes applied by Pallas to the sexual 
 animals of Ttenia. 
 
 FIG. 136. 
 
 FIGS. 135 and 136. Strobila and 
 Proglottis of Echineibothrium mini- 
 mum (after van Beneden). 
 
INDIVIDUALITY OF THE JOINTS. 
 
 275 
 
 We would not, however, conceal that there are, on the other hand, 
 certain tape-worms in which the sexual animals are never isolated, 
 and some indeed in which the jointing 
 is so incomplete that only an in- 
 distinct constriction (Tricenophorus) or 
 merely successive sets of generative 
 organs (Ligula) suggest the composite 
 nature of the body. If we compare 
 this state of matters with what we find 
 in other composite animals, we shall 
 not be led into error ; it only proves 
 that the independence of the united 
 individuals, or, if one prefer it, the 
 individualisation of the joints, is of 
 different degrees in different cases. 
 
 Even the external characteristics of 
 the tape-worms give us some standard 
 in judging of these degrees of indi- 
 vidualisation. The earlier and the 
 more sharply the individual joints are 
 marked off from one another, and the 
 looser their mutual association, the 
 greater will be their independence 
 in a biological sense. And thus it is 
 the typical forms of Tcenia, with their 
 narrow joints, like the seed of a 
 melon (Fig. 131), which most evidently 
 exhibit the polyzootic nature of these 
 animals. The joints separate singly, 
 and then in their movements and 
 behaviour appear as perfect, indepen- 
 dent individuals. In the broad, short 
 joints of the Bothriocepliali (Fig. 137), 
 this independence is not so marked, for 
 they are liberated, not singly, but in 
 groups of varying number. In the unjoin ted forms there is, of course, 
 no regular liberation. The individual parts are here subordinated to 
 the whole, both anatomically and biologically. 
 
 The forms hitherto mentioned do not, indeed, represent the highest 
 degree of centralisation possible to the Cestodes, for there are tape- 
 worms, as has been previously pointed out (p. 106), where the body 
 is destitute of any kind of joint. There is a short proglottis like 
 a flat-worm which contains only a simple generative organ, and is 
 
 FIG. 137. Bothriocephalus latus. 
 
276 CESTODES. 
 
 provided anteriorly with a more or less highly developed apparatus 
 of hooks (Caryophyllceus, Amphiptyches). In such cases there is no 
 distinction between nurse and sexual animal, or head and joint ; the 
 life-history, which is in ordinary cases spread over two generations, 
 is here perfected in the same individual ; instead of alternation 
 of generations a simple metamorphosis is seen. 
 
 Physiologically, the polyzootic tape-worm is a composite colony. 
 Sensation and movement, nutrition and excretion, are distributed 
 uniformly over all the joints, as if they were simply organs of one 
 individual and were not themselves individualised. In respect of 
 their functions they are, indeed, like organs, or "parts of a higher 
 unity," but the unity which they form and uphold by their combined 
 effort is, morphologically, not a single individual but a colony. 
 
 It was obviously these indications of a physiological unity which 
 hampered the true conception of the structure of the Cestode, and 
 ever recalled the old opinion that the tape- worm, even in its joitned 
 form, was a single animal. It was seen that the movements passed 
 as waves from one joint to another, that considerable portions of the 
 worm could extend their length, or, by contracting, increase their 
 breadth. How was this possible, except on the supposition of a 
 common and single impulse ? A number of canals were seen 
 running continuously throughout the chain; did not this prove the 
 individual simplicity of the body ? Was it not, after all, more 
 natural that the nurse should be regarded as the "head," and the 
 divisions filled with eggs as the "joints ?" 
 
 The physiological unity of a polymorphic community is not less 
 wonderful now than it ever was, but we have gradually become accus- 
 tomed to it. We see the same thing in every case where similar 
 conditions obtain. 1 Could one doubt that the bees of a hive form a 
 colony in spite of their separateness and various kinds, or that the 
 operations of the indisputably distinct individuals of such a colony 
 are not as mutually complemented and co-operative as if they were 
 directed by an individual will ? 
 
 But no more need be said in favour of a theory which is suffi- 
 ciently justified by the facts of development. 
 
 We have to distinguish, then, in the so-called "tape-worm" 
 two kinds of individuals the " head," originating the whole colony 
 (the "root" of Pallas, the "bulb" of Reirnarus), and the sub- 
 sequently produced "joints." At the first glance the latter differ 
 markedly from one another, the anterior joints near the head (the 
 " neck ") being small, and often indistinctly separated ; but all the 
 
 1 See my treatise on Polymorphism, referred to above. 
 
RADIATE ARRANGEMENT OF THE HEAD. 
 
 277 
 
 differences are simply dependent on age .and development. The an- 
 terior joints are the youngest, and therefore smaller and more im- 
 mature than the posterior, which have gradually attained 
 their full size and maturity. The chain furnishes us 
 with a perfect succession of developmental stages, and 
 consists sometimes of many hundred joints, though 
 sometimes of only a few, in Tcenia echinococcus of three 
 or four (Fi^. 138). 
 
 The differences between head and joints are, mainly, 
 that the former is provided with suckers and hooks, and 
 that the latter enclose highly developed hermaphrodite 
 reproductive organs. But besides this characteristic and 
 essential difference, there are many minor ones, so that in 
 fact hardly any common character can be mentioned. It 
 would be difficult to recognise a flat-worm in the head, 
 since it is usually pear- or club-shaped, and from the per- 
 fect similarity of the dorsal and ventral surface, conforms 
 rather to a radiate than to a bilateral type. This is FIG. 133. 
 most decidedly seen in the Tcenice, where the head Adult specimen 
 
 /T" 1 on\ i ji i i -it P f Twnia echino- 
 
 (tig. 139) is not only constantly provided with four coccus. (xi2.) 
 suckers, arranged two on either side round the longi- 
 tudinal axis, but bears also a neat circle of hooks on the apex, which 
 conform exactly to the architectural relations of the radiate animals, 
 both in their high number and regular arrangement. The interior 
 organs also, and especially the excretory vessels, show a distinct 
 radiate arrangement. In other cases the radiate structure is certainly 
 less striking ; for not only do the hooks often lose their circular ar- 
 rangement, and form groups corresponding in number and position 
 to the four suckers, or even wholly disappear, but even the structure 
 of the suckers changes. Sometimes the four approximate in pairs, 
 and fuse into two more or less simple suckers, thus assuming a bila- 
 teral arrangement ; or, instead of the lateral suckers, two median ones 
 appear, one on the dorsal and one on the ventral surface, as in the 
 genus Bothriocephalus (Fig. 1.40). 
 
 In contrast to this formation of the head, the sexual animals 
 possess an undeniable bilateral structure. This is, however, not 
 always shown with equal clearness and emphasis ; indeed, the lateral 
 symmetry is often disturbed, as also not unfrequently happens in 
 other bilateral animals. But it is only the generative organs which 
 are thus asymmetrical, the others lie on either hand in exactly the 
 same fashion. And sometimes even the generative apparatus is 
 quite symmetrical, as, for example, in the genus Bothriocephalus t whose 
 sexual animals are in a certain sense typical Cestodes. The genital 
 
278 
 
 CESTODES. 
 
 ducts and openings lie (Fig. 141) in the middle line, and are so 
 arranged that the openings are on that surface towards which the 
 
 FIG. 139. Apex and hooks of Tcmia solium. 
 
 FIG. 140. Head and anterior 
 portion of Bothrioccphalus cordatus. 
 
 female ducts are approximated, while the male organs lie near to the 
 opposite surface. According to the analogy of the Trematodes, the 
 former must be the ventral surface, and the latter the dorsal; and 
 among the Tamiadae also there are forms which exhibit like conditions, 
 as, for example, the Tcenia litterata of the fox. As a rule, however, 
 the genital openings are shifted from the middle to the side walls, 
 
 FIG. 141. Generative organs of Bothrio- 
 cephalus lotus (ventral aspect). 
 
 FIG. 142. Generative organs of 
 Tcenia solium. 
 
 and are found either all on one side, or on either side in an irregular 
 alternation (Fig. 142.) In such cases it would be hardly possible 
 to distinguish the dorsal and ventral surfaces, were it not that the 
 
ARRANGEMENT OF THE GENITAL OPENINGS. 279 
 
 position of the generative organs e.g., of the testes dorsally affords ns 
 certain fixed points for their determination. x 
 
 As we shall afterwards see, there are also Trematodes 
 with marginal genital openings, but their number is so small 
 that this position of the openings must be regarded only as ex- 
 ceptional, while in the case of the Cestodes it is almost the 
 general rule even outside the group of the Teeniadee. On a priori 
 grounds one would expect these peripheral openings to occur 
 on either side, but there are only few species 
 in which this is the case (Tcenia elliptica, 
 Tcenia expansa, &c., Fig. 143). In spite of 
 this, it must be regarded as forming the basis 
 of the common asymmetrical formation, and 
 this is proved by certain individual variations, 
 which we shall have further occasion to dis- 
 cuss particularly. Thus one finds, for example, 
 joints of Tcenia solium with symmetrical 
 marginal pores, and joints of T. elliptica occa- 
 sionally asymmetrical. In bilateral animals, 
 the unpaired mesial organs are, as is well 
 known, very often represented by two lateral 
 symmetrical organs. If further proof be FIG. 143. Sexually mature 
 needed of the morphological identity of the proglottis of T. elliptica. 
 lateral organs in Tcenia with the median structures of Botliriocephalus, 
 this might be noted, that in some species of Botliriocephalus (B. 
 fasciatus, B. tetrapterus), the genital openings lie, not, indeed, ex- 
 actly marginally, but regularly, right and left of the middle line. 
 And while this occurs here as a rule, it also appears as an exception 
 in other species. 
 
 The Anatomy of Cestodes. 
 
 Sommer and Landois, " Ueber den Bau der geschlechtsreifen Glieder von Bothrio- 
 cephalus," Zeitschr. f. iviss. Zool., Bd. xxii., pp. 40-100, 1872. 
 
 Schiefferdecker, " Beitrage zur Kenntniss des feinern Baues der Tanien," Jenaische 
 Zeitschr., Bd. viii., pp. 459-488, 1874. 
 
 Steudener, " Untersuchungen iiber den feinern Bau der Cestoden," Abhandl. d. 
 naturf. Gcsellsch. zu Halle, Bd. xiii., pp. 277-366, 1877. 
 
 Kahane, "Taenia perfoliata, als Beitrag zur Anatomic und Histologie der Cestoden," 
 Zeitschr. f. wiss. Zool., Bd. xxxiv., p. 175, 1880. 
 
 1 In the first edition of this work I called attention to the peculiar distribution of the 
 generative organs of Ta>nia>, and indeed of Cestodes generally. My conclusions have since 
 been corroborated, especially by Kahane (Zeitschr. f. wiss. Zool., Bd. xxxiv., p. 214, 1880), 
 and by Moniez (Bullet, scientif. dfp. du Noi'd, p. 220, 1878), who has, indeed, failed to 
 notice my previous observations on the subject. 
 
280 THE ANATOMY OF CESTODES. 
 
 In our general discussion of the flat-worms we have already noted 
 that the Cestodes are parenchymatous animals. The whole body is 
 one mass, the continuity of the tissues is not broken by any visceral 
 cavity. The vegetative organs are embedded in the general substance 
 just like muscles or nerves. 
 
 The simplest and most convincing proof of this is furnished by 
 their longitudinal and transverse sections, which are easily cut from 
 carefully hardened specimens, and which, with the help of the now 
 familiar staining and clarifying reagents, show the structure of the 
 organism most beautifully. 1 
 
 The Body-Parenchyma. The mass of the Cestode body is in its 
 morphological and histological relations a hyaline connective tissue 
 of varying firmness, and developed so abundantly that one can almost 
 fancy that the whole body of the animal has been modelled out of it. 
 Externally, it is surrounded by a cuticle which is elevated at many 
 points, especially on the head, into little spikes and hooks. The in- 
 terior of the body, apart from the viscera, is traversed by muscular 
 fibres, which run sometimes singly, sometimes in bundles, and 
 generally in all three dimensions of space, so that the body-mass 
 can be contracted on all sides. The more conspicuous are the 
 longitudinal and transverse fibres, which at some distance from the 
 exterior are developed in such numbers, and so close to one another, 
 that the whole body-parenchyma is thus divided into two successive 
 outer and inner sheaths, which (following Eschricht) we will respec- 
 tively designate as "cortical layer" and "middle layer." 2 
 
 The middle layer is seen on cross section to be bounded externally 
 by a narrow clear border 3 (the strong muscular bands), and includes 
 the generative organs, the longitudinal vessels, and the nerve cords ; 
 while the cortical layer mainly consists of the numerous muscular 
 fibres, and a considerable number of round, solid, laminated concre- 
 tions the so-called "calcareous bodies " which contain a considerable 
 but varying proportion of lime salts. 
 
 1 I need hardly mention that such methods were but little known or practised when 
 the first edition of this work appeared (1862). So far as I know, I was the first to 
 apply them to the investigation of Helminths, or indeed of Invertebrata in general. I 
 mention this not to claim credit for it, but as an excuse for the errors which crept into 
 my former account, largely in consequence of my necessarily imperfect methods. 
 
 2 The latter includes the "transparent " layer distinguished by Eschricht in Bothrio- 
 cephalus latus, and also the so-called ventral and dorsal granular layers. See Nova Actn 
 Acad. Cces. Leop.-Carol., t. xix., Suppl. 2, 1841. 
 
 3 Pagenstecher believes (Zeitschr. f. wiss. Zod., Bd. xxx., p. 177, 1878) that he can dis- 
 tinguish a narrow space within the muscular layers of Tcenia critica. This he would repre- 
 sent as a body-cavity. I have never seen any such appearance in my examination of 
 numerous species. 
 
NATURE OF THE CALCAREOUS BODIES. 281 
 
 They are not, however, exclusively confined to the cortical sheath, 
 but are also to be found in the 
 middle layer, only sparsely, 
 however, in the mature joints, 
 though indeed in considerable 
 numbers before the develop- 
 ment of the sexual organs. We 
 
 , ,, ,, . FIG. 144. Cross section of Tcenia solium, 
 
 must alSO note that tlieir showing middle and cortical layers, under low 
 
 number varies not only in indi- power. 
 
 vidual cases but in the different species, and this to such an extent 
 that one sometimes looks for them almost in vain, while in other 
 cases they are present in extraordinary abundance. 
 
 In the Bothriadse, as we shall afterwards see, the cortical layer 
 also includes the numerous cell-groups which form the yolk-glands 
 (Eschricht's ventral and dorsal granules). 
 
 The connective tissue nature of the ground substance has been 
 recognised on all hands since the publication of my researches in the 
 first edition of this work. Opinions differ, however, as to its exact 
 histological structure. I still maintain that it partakes of the nature 
 of cellular connective tissue. The cells are indeed seldom prqvided 
 with a distinct cell membrane, in fact they are usually mere nucleated 
 masses of clear protoplasm, and sometimes (especially in the ripe 
 joints) are fused together into a mass, leaving only their nuclei 
 distinct. But these characters not unfrequently occur in connective 
 tissue. In other cases one can observe a distinct intercellular 
 substance usually in the form of a tolerably well-defined cubical 
 network of bands and fibres, with cells of various sizes (up to O'Ol 
 mm.) lying in the meshes. Here and there the nuclei are so closely 
 appressed to the intercellular substance that one can easily mistake 
 the fibres for processes of special cells. There are, indeed, in the 
 parenchyma of the Cestodes true fibre -like cells, some spindle- 
 shaped, some multipolar, the former lying in the so - called sub- 
 cuticular sheath, as we shall afterwards have occasion to notice. 
 The multipolar cells, which have been hitherto noticed only by 
 Schiefferdecker, possess a membraneless, finely granular protoplasm, 
 enclosing a very distinct nucleus, and running out into a varying 
 number of long, thin, sometimes even reticulated processes of a 
 similarly finely granular nature. They are found scattered through 
 the whole parenchyma, especially in large Tcenice, and sometimes 
 recall ganglion cells. 
 
 The Calcareous Bodies. We have already noticed these as distributed 
 through the body-parenchyma, and belonging specially to the cortical 
 layer. These concretions vary in size up to O'Ol 9 mm., and have a 
 
282 THE ANATOMY OF CESTODES. 
 
 generally spheroidal, but often elliptical or kidney-like shape. In 
 their solidity, in their power of refraction, and above all in their more 
 
 or less distinct concentric lamination, they 
 rem i n( l one f starch grains. Sometimes 
 the central mass is distinguishable like a 
 nucleus from the surrounding substance, 
 which is occasionally radiately arranged. 
 FIG. 145. Calcareous cor- In some cases the bodies form twins, with 
 5S2' 8hOWiDg two or three centres and an irregular 
 
 form. 
 
 Very varied opinions have been held as to the nature of these 
 calcareous bodies since they were first described by Pallas and Goze. 
 In the bladder-worms, where they often occur in most extraordinary 
 abundance, they were frequently regarded as eggs, or as blood and 
 lymph corpuscles. It was only after the lapse of some time that 
 Doyere and others proved that they were mainly composed of car- 
 bonate of lime. This altered the nature of the current explanations, 
 and v. Siebold, reasoning on the analogy of similar bodies in the lower 
 animals, claimed them as skeletal, while Claparede thought they were 
 the results of an execretion. 1 This opinion was based on an observa- 
 tion made in the first instance on a Trematode-larva, but which seemed 
 to shed a new light on the nature of these bodies in the Cestodes. 
 Claparede thought he had clearly established that these structures 
 were not freely embedded in the body-parenchyma, but were sur- 
 rounded by pouch-like dilatations of the terminal branches of the 
 excretory system. Although I formerly believed myself warranted 
 in confirming these conclusions from an investigation of an oceanic 
 Cestode 2 (the Echinobothrium of the ray), which I conducted along 
 with Pagenstecher, and indeed attempted in the first edition of this 
 work to support the above theory, and to remove the physiological 
 arguments against it, yet I feel myself now compelled, along with 
 other investigators (Eindfleisch, Landois and Sommer, Schiefferdecker), 
 to adopt v. Siebold's opinion. I must, however, leave it undecided 
 whether these bodies have any other functional significance than as 
 supporting or protective structures. 
 
 It would, however, be a mistake to suppose that the designation 
 " calcareous bodies " implied that these structures were wholly com- 
 posed of lime. In the tape-worms they do indeed contain in many 
 cases a very large proportion of lime 3 21 per cent, of salts (mostly 
 
 1 Zeitschr.f. wiss. Zool., Bd. ix., p. 99, 1858. 
 
 - " Untersuchungen liber niedere Seethiere," Mutter's Archiv f. Anat. u. Physiol., 
 p. 605, 1858. 
 
 3 There are, besides, small quantities of magnesia, oxide of iron, soda, and potash. 
 
FUNCTION OF THE CALCAREOUS BODIES. 283 
 
 calcium salts) in the case of a newly examined Tcenia marginata, 
 according to an analysis made at my request by Professor Naumann 
 in Giessen. But the most superficial micro-chemical examination 
 reveals in the calcareous bodies the presence of an organic mass whicl 
 is associated with the lime, and which can even be isolated as a clear 
 ball of the original size by dissolving out the lime with an acid. Since 
 this process is accompanied with more or less effervescence, the lime 
 is therefore, for the most part, though we cannot say exclusively, 
 deposited as carbonate of lime. 
 
 In some cases the bodies do not effervesce on being treated with 
 acid, and this even in some species where they have previously been 
 observed to do so. I tried formerly to explain this fact by the suppo- 
 sition that the carbonate had been replaced by some other salt of lime, 
 but I have been informed by Sommer and Landois that small quantities 
 of carbonic acid gas, instead of escaping in bubbles, are absorbed in 
 statu nascente by the surrounding fluid, and that thus the absence of 
 effervescence is in no way a sign of a complete absence of carbonic 
 acid gas. 
 
 That effervescence should be absent when the calcareous bodies 
 are present in smaller numbers, seems to me hardly to explain why it 
 should be absent under certain circumstances in forms which usually 
 exhibit it. Nor is the development of gas observed in all the cor- 
 puscles in equal intensity. Since they also differ markedly in appear- 
 ance, lustre, and power of refracting light, I think we may assume 
 that not only the number, but the composition of these calcareous 
 bodies, is subject to manifold individual and specific variations. 
 
 It appears to me a mistake to regard the calcareous bodies of the 
 Cestodes as unalterable and permanent structures. As they arise and 
 increase during the development of the joints, so they under some 
 circumstances decay. This is most, easily observed in species where 
 they are numerous. Thus Tcenia serrata is not only much more richly 
 provided with them in its cysticercoid stage than later, but it at first 
 possesses them abundantly in the middle layer of the proglottides, 
 where they afterwards often almost wholly vanish in the more mature 
 stages. We are irresistibly reminded of the history of the so-called 
 " crab-stones," which are known to represent reserve materials ; and 
 we are well aware of various epochs .in the life -history of Cestodes 
 when there is a temporary demand for a large quantity of lime, and 
 especially of carbonate of lime, e.g., to neutralise the acid digestive 
 juices, and to form and harden the egg-shells. 
 
 Phosphoric, carbonic, hydrochloric, and sulphuric acids have also been detected. The ashes 
 yielded a smaller quantity only 4'9 per cent. but this was in the case of a specimen 
 of Tcenia solium which had been kept for long in spirits. 
 
284 THE ANATOMY OF CESTODES. 
 
 Virchow first suggested that the calcareous bodies of the Cestodes 
 arose from connective-tissue corpuscles; but although the majority 
 of subsequent observers have supported this opinion and Schieffer- 
 decker considers that lie has even followed the process through all its 
 phases, 1 the cellular origin of these bodies seems now hardly 
 plausible after Harting's 2 beautiful investigations, in which he shows 
 the origin of the various forms occurring so abundantly among the 
 lower animals, and particularly of those which now interest us. The 
 presence of a formed specific organic substratum is by no means 
 necessary, as was formerly believed ; it is sufficient if an amorphous 
 or fluid organic substance be present, with which the carbonate of 
 lime may incorporate itself. If the formation occur in ordinary 
 albumen, then calcareous bodies arise of exactly the same form and 
 nature as those of the Cestodes, agreeing with them also in that they 
 exhibit the same clear residue (" Calcoglobulin," Harting) after 
 dissolving away the lime, and they repeat in their individual 
 divergences all the variations above noted. 
 
 There remains, indeed, no reason for connecting the origin of these 
 calcareous bodies with any special cellular structures in the body of 
 the Cestodes. From suitable preparations, and especially from the 
 larval cystic stage at the time of the formation of the head, one can 
 distinctly convince oneself that they arise without the help of cells. 
 They originate as small roundish grains, having from the first their 
 peculiar optical and chemical properties, and attain their subsequent 
 size by peripheral growth, i.e., by the deposition of successive sheaths. 
 
 All the intermediate stages observed between the calcareous bodies 
 and connective tissue cells are, in my opinion, merely concretions, 
 with slightly or unequally distributed lime contents that is to say, 
 calcareous bodies which contain only a small quantity of inorganic 
 substance, either because it has only been partially deposited, or be- 
 cause the degeneration above referred to has set in. 
 
 The Cuticle. On its surface the parenchyma of the Cestod^s bears 
 a clear unciliated elastic skin, which shows no trace of its elementary 
 
 1 Schiefferdecker describes the development of the calcareous bodies as follows 
 (loc. '., p. 470): "The doubtful cell first surrounds itself with a membrane. The 
 protoplasm has not its normal appearance ; the granules are further separated ; it looks as 
 though the cell-contents were diluted. The cell becomes more and more invaded by fluid, 
 the protoplasm shrinks round about the nucleus, which then looks like a ball floating in the 
 fluid contents of the celL The protoplasm seems still further to disappear, at least only 
 the nucleus remains, and that without its nucleolus. The calcification begins from the 
 nucleus, it works its way out in distinct /ones to the periphery, till the calcareous body is 
 finished. I have never seen any connection between the calcareous bodies and the excre- 
 tory canals, nor can I tell why so many connective tissue cells calcify." 
 
 2 " Recherches de tnorphologie synthe'tique, &c.," Naturk. Vcrh. koninkL Akad., Deel 
 xiii. : Amsterdam, 1873. 
 
NATURE OF THE CUTICLE. 285 
 
 composition, but is perfectly homogeneous. Both in this respect and 
 in its chemical composition (as shown with regard to Ecliinococcus) 
 this skin reveals its essentially cuticular nature. The thickness 
 of this cuticle varies exceedingly, and not always in proportion to 
 the size of the animal, although as a rule the larger species have 
 the thicker covering. It ought not, of course, to be overlooked that 
 the thickness and firmness of the cuticle is very different at different 
 parts of the body. The cuticle is thickest in the bladder-worm of 
 Tcenia echinococcus, which sometimes grows to the size of a child's 
 head, or even larger. In this case it shows a very striking lamination, 
 often hardly perceptible in other cases. When the cuticle attains a 
 certain thickness, it possesses a more or less distinct vertical striation, 
 which is, of course, fine, and only visible by the use of a high power. 
 This is of great importance, however, for these organisms, since it is 
 caused by the presence of thickset pores, by means of which the 
 absorptive power of the skin the only absorbing organ in these 
 asplanchnic Cestodes is greatly increased. The pores can some- 
 times be observed on surface inspection as fine, thickly studded little 
 points, some bright, some dark, according to position of the microscope- 
 tube. 
 
 We owe the detection of these pores to the researches of Sommer 
 and Landois, whose results have been fully confirmed by subse- 
 quent observers. All unite, too, in emphasising their nutritive im- 
 portance, but this is represented in a way which I cannot but con- 
 sider erroneous. According to this theory, the pores are not in them- 
 selves directly efficient in nutrition, but only in so far as they serve 
 for the protrusion of fine protoplasmic threads, which are in direct 
 continuity with the subcuticular tissue to which they thus pass on 
 the food. This theory is especially maintained by Schiefferdecker, 
 who has tried to establish it to the minutest details. 
 
 In suitable preparations it is not difficult to observe, as I have 
 myself done in my earlier investigations, that the cuticle, when intact 
 arid of considerable thickness, bears, at certain intervals, a fringe of 
 fine rods or threads. These are about as long as the cuticle is thick, 
 have a granular nature, and " forcibly remind one of similar structures 
 sometimes exhibited on the outer surface of intestinal epithelial cells 
 in Mammalia." 1 They are not unfrequently "so thick that they 
 look as though the outer surface of the worm were covered with 
 a thin layer of granular protoplasm." 1 I attached no special physio- 
 logical importance to these structures, simply because I could only 
 regard them as anatomically very unimportant, namely, as the re- 
 mains of an older exfoliated and altered cuticle, or, in other words, 
 
 1 Quoted from Landois and Sommer (loc. tit.). 
 
286 THE ANATOMY OF CESTODES. 
 
 as the result of a moulting. This opinion I still maintain, even more 
 firmly than ever, and believe that I can support it on indisputable 
 grounds. 
 
 I base my arguments mainly upon the state of affairs in the 
 bladder-worms, where this outer fringe may be quite regularly ob- 
 served, but not on the absorptive, i.e., the outer surface of the bladder, 
 but in a situation where this is impossible namely, in the canal-like 
 interior space of the so-called head, which is merely the future head 
 of the tape-worm in its invaginated state. 
 
 The cuticle which clothes this head is therefore turned inwards 
 towards the above-mentioned canal space, and is repeatedly thrown 
 off and changed as the head rapidly grows. The cast cuticles remain 
 lying in the interior of the space, and more or less fill it. They have 
 exactly the finely granular appearance and the loose texture of the 
 usual fringe, except that they usually hang together as a membrane, 
 and only rarely, and that imperfectly, fall into rods. The outer that 
 is, the youngest of these layers for two or three can sometimes be dis- 
 tinguished is in more or less close connection with the cuticle, just 
 as is the fringe with the cuticle of the tape-worm. 
 
 I attach no special weight to the fact that the latter often takes 
 the form of a border of more or less distinct rods. This certainly does 
 not occur so generally and constantly as we are led to infer from 
 the reports of Schiefferdecker and Steudener, who speak of nothing 
 but "little hairs," or "cilia." It is, indeed, occasioned by the 
 rupture which follows in consequence of the increase of surface in 
 the growing proglottides, by forces, therefore, which were not so 
 powerful in the inverted head of the bladder-worm, which was re- 
 stricted in its longitudinal extension. I need hardly notice further 
 that the presence of the pore-canals must be a factor in the process. 
 The liberation of the so-called " covering membrane " on the above- 
 mentioned epithelial cells is only possible because of the pore-canals 
 which penetrate it. 1 
 
 When I finally note that the connection between the proto- 
 plasmic threads and the subcuticular tissue has never been seen by 
 any one, but only imagined for the sake of the theory, and seems 
 in the highest degree improbable when we consider the histological 
 structure of this tissue, then I think I have said enough to show how 
 untenable that theory is, which attempts fundamentally to alter our 
 conception of the nature of endosmotic nutrition. 
 
 The cuticle is, on the whole, flat and smooth, but is raised at 
 certain points into little hairs, prickles, and hooks, which vary ex- 
 tremely in form and size. 
 
 1 Compare also similar conditions in the cuticle of the tubules of Rainey or Miescher 
 (p. 201). 
 
THE SUBCUTICULAR LAYER. 287 
 
 The most conspicuous and important of these elevations are the 
 hooks which are situated on the apex of the Cestode head, and which, 
 are instrumental in fixing the head, and hence the whole worm, to 
 the intestinal wall of the host. The structure and arrangement of 
 these hooks are also of great systematic importance, as we shall see in 
 the course of our exposition. 
 
 The study of the development of these organs shows that not 
 only are all the hooks reducible to the same primitive form, but 
 also that hooks, spines, and little bristles, in fact all the cuticular 
 appendages, are referable to a common type. This primitive form 
 is simply a little cone, seated on a papilliform elevation of the sub- 
 cuticula, and arising from the hardening of its outer surface, which 
 is at other points also sometimes of a firmer character. If these 
 
 FIG. 146. Development of the hooks of Tcenia serrata. 
 
 cones remain small and thin-walled, then we have the common form 
 of hair or spine. When they grow gradually stronger and bend, 
 and when the continued deposition of skeletal substance renders 
 them even harder, then there arise the characteristic forms of the 
 true hooks. Finally and particularly, in the Tcenice they develop 
 a special process on their lower border, and having formed a well- 
 developed basis or root, become the familiar independent and often 
 even moveable hooks. 
 
 The fully developed hook has a very considerable strength, owing 
 to the thickness of its walls, and to the deposition of carbonate of lime. 
 This strength is gradually acquired as the layers are deposited in- 
 ternally, and slowly hardened. In many cases one can detect the 
 successive layers, even in the full-grown hooks, by the lines running 
 down the hook parallel to the outer surface. The thicker the wall 
 the narrower does the internal space become, and in many species it 
 wholly vanishes. 
 
 The Subcuticular Layer. We usually regard the cuticle of animals 
 as the excretion of an epithelial layer of cells, and we often find, lying 
 below it, a tissue of more or less distinct cellular character. Such a 
 subcuticular layer has often been sought for in the Cestodes. I 
 
288 THE ANATOMY OF CESTODES. 
 
 was formerly of opinion that the analogue of the ordinary subcuticula 
 . was to be found in a " richly granular parenchymatous layer," dis- 
 covered by me under the cuticle. Although this layer has a peculiar 
 structure, and is but imperfectly marked off from the subjacent tissue, 
 my opinion was followed by subsequent observers, except Eindfleisch, 1 
 and the layer in question was even credited with a distinct cellular 
 structure. The most distinct description is furnished by Steudener, 
 who asserts that the subcuticular layer consists, in all Cestodes, of 
 extended, narrow, conical cells, which stand together like a palisade, 
 with the summits of the cones directed inwards, and with the bases 
 resting on the cuticle. Each cell has an oval nucleus, often slightly 
 broader than the cell itself, which, therefore, must bulge out at that 
 point. The nuclei lie in the middle of the cell, sometimes nearer the 
 summit, sometimes nearer the base, so that in a vertical section they 
 are not seen in a line, but irregularly alternating in a somewhat broad 
 zone. The two halves of these cells differ strikingly in their optical 
 and histological characters, for the basal portions are homogeneous, 
 while the other halves consist, according to Steudener, of a granular 
 protoplasm, in which the boundaries of the cells are but faintly dis- 
 tinguishable. 
 
 An inspection of sufficiently thin and well-stained preparations 
 of Tcenia is quite enough definitely to prove that this sub-cuticular 
 layer is formed, not of mere granules, but of cells usually arranged 
 perpendicularly to the cuticle. It is not, however, so easy to accept 
 Steudener's reports as to the nature of these cells. I am unable to 
 resolve the finely granular outer layer into tops of individual cells, and 
 cannot therefore regard them as cylindrical cells. They seem to me 
 rather, as they formerly appeared to Eindfleisch and Schiefferdecker, 
 as spindle-shaped cells, whose protoplasm lies round about the oval 
 nucleus in a thin layer, and runs out at both ends into thin threads. 
 The outer ends lie against the cuticle, while the inner threads may be 
 followed some distance into the body-parenchyma, and, as I have often 
 observed, may come into distinct connection with the very fine trans- 
 verse muscular fibres. 
 
 Nor can I recognise in these cells the matrix cells of the cuticle, 
 but agree with Eindfleisch in regarding them merely as peculiarly 
 formed connective tissue cells. I am further confirmed in this opinion, 
 since the cells in question sometimes lose their spindle form, and look 
 exactly like the connective tissue cells of the Cestodes. Thus it is, 
 for example, in the head of the tape-worms, in the parts connecting 
 the individual joints of Tcenia saginata (Fig. 147), and in the leaf-like 
 
 1 "Zur Histologie der Cestoden," Archiv /. milcrosk. Anat., Bd. i., p. 140, 1865. 
 
STRUCTURE OF THE SUBCUTICULAR LAYER. 289 
 
 or lappet-like prolongations of the side-walls of T. perfoliata. Hence 
 the transverse muscles are but slightly developed at these points, and I 
 feel almost inclined to suppose that there is some connection between 
 them and the spindle-shaped cells, especially since the latter have, as 
 has been mentioned, been seen in direct connection with the former. 
 When one further notes that the direction of the spindle-cells in the 
 long-jointed Tcenice (Tcenia saginata, &c.) varies at the ends of the 
 proglottides in conformity with the muscle-fibres, one feels almost 
 warranted in regarding the spindle-shaped or subcuticular cells as a 
 sort of tendinous fibres. 
 
 In agreement with this we may note that the spindle form of the 
 cells in question is but inconspicuous in the Bothriocephali (B. latus), 
 which have a poorly developed musculature. The filiform ends are 
 extremely delicate, and are very easily overlooked ; the cells them- 
 selves are closely grouped together in a thick layer. With the excep- 
 tion of the peculiar grouping, they exactly resemble the ordinary 
 connective-tissue cells of the rest of the parenchyma. 
 
 If the above theory of the subcuticula be correct, then the Cestodes 
 have no epithelial membrane covering the body, and the same will 
 be true of the Trematodes. The cuticle cannot be genetically com- 
 pared with the cuticle of the lower animals ; it is rather the structure- 
 less limiting membrane of the connective-tissue substance, and is 
 comparable with the so-called basement membrane found in the other 
 flat-worms, and especially in the Planarians-, between the muscular 
 layer and the dermal epithelium. 
 
 This is, indeed, a theory which has been formerly repeatedly main- 
 tained, particularly by Schneider, 1 and was suggested especially in 
 connection with the embryos of some species which throw off their 
 ciliated epithelium. Minot reports having seen, even in the adult 
 stages of Caryophyllceus, Tcenia, Botliriocephalus, &c., distinct cylindri- 
 cal cells on the uninjured cuticle. 2 This must, however, rest on a 
 confusion with the above described excreted layer. 
 
 The histological and chemical nature of the Cestode cuticle can 
 hardly be used as an argument against regarding it as comparable 
 to the basilar membrane, for we know that in the lower animals 
 the connective substance occasionally assumes a thoroughly cuticular 
 character. 3 The only argument against this theory is the dogma 
 according to which the outer surface of every animal should during 
 
 1 " Untersuchungen iiber Plathelminthen, " Vierzehnter Bericht d. oberhess. Gesellsch. 
 Natur- u. Heilkunde, p. 69, 1873. 
 
 2 " Studien an Turbellarien " (loc. cii.), p. 456. 
 
 3 I may refer to my observations on the intermuscular connective substance of the 
 Nematoda and Acanthocephali : see Vol. II. 
 
 T 
 
290 THE ANATOMY OF CESTODES. 
 
 life be clad with an epithelial layer the ectoderm. But general 
 statements of this kind must vary with the growth of our experience, 
 and it is only to the results of experience that we can attach 
 decisive importance. 
 
 Yet another argument against the prevalent explanation of the 
 so-called subcuticula as an epithelial layer is found in the fact that 
 it is not directly adjacent to the cuticle, but is in fact separated from 
 it by a layer of fibres crossing at right angles. 
 
 Our attention is first directed to the existence of this peripheral 
 fibrous layer by the appearance of a thin section of the skin, which 
 shows on its surface a delicate, extremely fine lattice- work. The lines, 
 which form this, run very regularly transversely and longitudinally, 
 and turn out on further examination to be the contours of fibres, 
 which are arranged one over the other in simple layers. The outer- 
 most are the transverse or circular fibres, which form a continuous 
 sheath, while the longitudinal fibres are separated by interspaces, 
 through which run the external processes of the spindle-shaped cells. 
 
 This difference between the two layers of fibres is obviously the 
 reason why many investigators have claimed for each a distinctive 
 character. The longitudinal fibres have been very generally regarded 
 as muscles, but those running circularly have sometimes been regarded 
 as connective-tissue fibrils (Rindfleisch), and sometimes as integral 
 parts of the cuticle (Schiefferdecker and Steudener). Only a few 
 observers (Leuckart, Nitsche, Schneider) have regarded them as a 
 layer of circular muscle fibres. 
 
 I still hold to the last opinion, because if the fibres of the two 
 layers be observed under the same conditions, they have the same 
 optical characters; and, besides, there are cases, as in the so-called 
 caudal bladder of the Cysticerci, where both circular and longitudinal 
 fibres are in their thickness and microscopic characters undeniably 
 muscular. They are indeed usually paler and narrower than most 
 muscle fibres, but these present so many striking differences that one 
 cannot lay much weight on such peculiarities. 
 
 After this discussion of the facts of the case, I do not think that 
 I am wrong in claiming the subcuticular fibrous structure of the 
 Cestodes as a musculo-dermal layer. 1 The other muscles penetrating 
 the connective substance of the body might then be called the 
 parenchymal muscular system. 
 
 1 Previous investigators have also sometimes spoken of a musculo-dermal layer in the 
 Cestodes, meaning thereby usually the muscles of the cortical sheath, including generally 
 the transverse fibres surrounding the middle layer. These I designated, not quite cor- 
 rectly, in the first edition of this work as the layer of circular fibres, and indeed as the 
 " deeper" or "inner" layer, as distinguished from the subcuticular system. 
 
THE PARENCHYMAL MUSCLES. 
 
 291 
 
 The Muscular System. The fibres of which this consists are some- 
 times separate, sometimes united, but in the adult stages run so 
 regularly in the three dimensions of space, that one can fitly designate 
 them longitudinal, transverse, and sagittal muscles. As in other 
 animals without a skeleton adapted for locomotion, these muscles are 
 wholly composed of smooth or so-called " organic " fibres. One looks 
 indeed in vain for a nucleus, at least in those which are full-grown. 
 They consist of a perfectly homogeneous, strongly refractive proto- 
 plasm, showing at most, and that only in the thick fibres, a differen- 
 tiation into peripheral and axial substance. The ends are narrowed 
 and drawn out into more or less long- 
 threads, not unfrequently dichotomising. 
 On the isolated fibres one often sees late- 
 ral processes, as thin, delicate filaments, 
 forming sometimes a distinct network. 
 One may even hazard the supposition that 
 the intercellular network above described 
 was of a muscular nature. 
 
 These parenchymal muscles attain 
 their greatest development in the musculi 
 longitudinales which occur in all Cestodes, 
 and which run, especially down the inner 
 part of the cortical layer, in the form of 
 numerous strong bands (Fig. 147). This 
 is most distinctly and most beautifully 
 seen in the younger joints, where the 
 fibres are arranged in closer groups, 
 though they are of course much shorter 
 than is afterwards the case. These deeper 
 bands exhibit the thickest fibres the 
 thickest, indeed, in the whole body. Ex- 
 ternally both bundles and fibres thin off, 
 sometimes gradually, sometimes suddenly, 
 until in the close neighbourhood of the 
 cuticle we only find the fine isolated 
 fibres. In many cases these can be followed into the longitudinal 
 fibres of the musculo-dermal sheath, so that the distinction between 
 the two systems becomes somewhat fictitious. 
 
 Like the longitudinal muscles, those which run transversely are 
 usually well developed, and grouped in bands of considerable 
 strength. This is at least true of the main mass of those fibres, 
 which bound the middle layer, and which (except in Tcenia undulata 
 and a few others) are almost united into a continuous layer, lying 
 
 FIG. 147. Longitudinal section 
 of Tcenia saginata (young chain of 
 joints). ( x 25.) 
 
292 THE ANATOMY OF CESTODES. 
 
 under the longitudinal bands. With a low power it often appears 
 as though we could, in a cross section, follow these fibres in a 
 ring round the middle layer (Fig. 144), but in reality we have here 
 to do with two flat muscular plates, whose fibrous bands enclose the 
 middle layer, and expand at the sides of the joints (Fig. 148) into 
 
 FIG. 148. Cross section of a somewhat older joint of Tcrnia 
 saginata. ( x 38.) 
 
 a fan shape towards the cuticle. Inasmuch as the bundles on either 
 side often converge, and even occasionally cross, it appears as if they 
 were in continuous connection ; and this is especially so, since many 
 of the sagittal muscles also usually bend round, and surround the 
 middle layer. It is not, however, only at the lateral borders of the joint 
 that the transverse fibres bend from their normal direction towards 
 the cuticle; the same appearance is to be observed (Fig. 148) here 
 and there throughout the rest of their course. This occurs sometimes 
 at so many points, especially in the young joints, that the longitudinal 
 muscles, separated by the processes, assume an almost radiate arrange- 
 ment, and present an appearance which reminds one of the fibrous 
 groups in the cortical layer of the spinal cord. 
 
 Finally, as to the sagittal muscular fibres, these are mostly isolated 
 or united in slender bundles, which are stretched between the two 
 surfaces of the tape-worm, and were hence originally described by me 
 as dorso-ventral muscles. They are the thinnest of all the parenchymal 
 fibres, and run as fine fibrils almost straight across the whole thick- 
 ness of the body through both layers. In the outer layer they form 
 almost the only contractile elements, other niuscle fibres being but 
 rarely present to any considerable extent. It is, however, only in 
 their earlier stages that the sagittal fibres run at all straight, for the 
 development of the generative organs which finally grow throughout 
 the whole of the middle layer naturally influences their arrangement, 
 and often alters their direction. 
 
MODE OF CONNECTION OF THE JOINTS. 
 
 293 
 
 It is not necessary to enter into details as to the working of the 
 above-described muscles. It is easy to understand that the longi- 
 tudinal fibres shorten the body, while the other muscles give rise to 
 elongation by lessening the diameter. Their action is aided by their 
 general connection with the cuticle, as well as with the surrounding 
 body-parenchyina. We have already emphasised this fact, and also 
 the probable function of the subcuticular cells. 
 
 It is not only the transverse and sagittal fibres which exhibit a 
 connection with the latter. It can also be demonstrated of the longi- 
 tudinal fibres, at least in those cases where the individual joints are 
 sooner or later separated from one another. Then one sees that the 
 longitudinal fibres do not run continuously throughout the whole 
 worm, as in the unsegmented forms and in the anterior imperfectly 
 separated portions of other forms, but pass at the joints into a number 
 of fine threads, by means of which they are inserted into the folds of 
 the constricted cuticle. 
 
 I am most intimately acquainted with the state of matters in 
 Tcenia saginata, in which there is an 
 almost neck-like isthmus connecting two 
 adjacent joints, in itself well marked off 
 from the rest of the body-mass, both histo- 
 logically and otherwise. Especially one is 
 struck with the poverty of the muscula- 
 ture, and with the absence of the spindle- 
 shaped cells, usually placed at right angles 
 to the cuticle. Muscles are not, however, 
 wholly absent. With a high power one can 
 recognise a number, not only of sagittal 
 but also transverse fibres ; both are, how- 
 ever, much sparser, and, the latter espe- 
 cially, markedly thinner than usual. No 
 longitudinal fibres can be detected. They 
 all end near the boundary of the joint, 
 sharply and suddenly, so that there is no 
 doubt that the joints are, thus far at least, 
 independent. The connection between 
 them is effected by spindle cells, which 
 look exactly like those of the subcuticula, 
 except that they are not seated on the 
 cuticle, but are embedded longitudinally 
 in the clear ground mass. Here and there 
 one can plainly see how the fine end of a fibre comes into union 
 with a connective-tissue fibril, and is thence connected by a whole 
 
 FIG. 149. Longitudinal section 
 of Tcenia saginata. (x 25.) 
 
294 THE ANATOMY OF CESTODES. 
 
 series of spindle cells with the longitudinal musculature of the neigh- 
 bouring joint. It is, however, only the deeper layer of the longitudinal 
 muscles which exhibits this relation. The more superficial fibres 
 have indeed their spindle cells, but these bend at an early stage out 
 of their longitudinal direction and attach themselves to the cuticle. 
 They resemble the ordinary subcuticular cells, except in this, that 
 they do not lie at right angles to the cuticle, but at an acute angle 
 corresponding to the direction of the connected fibres. This cannot, of 
 course, be considered an essential difference, since even the sub- 
 cuticular spindle-cells bend from their normal direction at the in- 
 curved terminal borders of the proglottides, and apply themselves to 
 the cross muscular fibres, here bent into the form of a bow (Fig. 149). 
 These arrangements are best studied on sagittal longitudinal 
 sections, which show us further that (Fig. 149) the middle layer of 
 the individual proglottides, although passing through the isthmuses 
 without interruption, and thus, like the cortical layer, running the 
 whole length of the worm without breach of continuity, 
 differs widely at various situations in the structure of 
 its sagittal muscles. Not only do these become con- 
 siderably stronger at the ends, but they curve into 
 little arches, as has been already noted (p. 291). In 
 this way the generative organs are, to some extent, 
 bounded and restricted in the individual joints. 
 
 There is no need to point out how much the libera- 
 tion of the proglottides is facilitated by the above 
 arrangements. It is also evident that the liberation 
 will be effected by muscular contraction. I believe 
 that the sagittal muscles are by their structure specially 
 efficacious in the process of liberation, for they are able 
 by contraction to flatten themselves, and thus con- 
 laat joints of^nS siderably to expand the middle layer. It is, indeed, 
 saginata about to the middle layer which first ruptures, while the peri- 
 befibe fat. plieral p arfcg ^ and es p ec i a iiy the lateral borders, often 
 
 retain their connection for a while (Fig. 150). 
 In the interior of the head the arrangement of the muscles has 
 been specially modified on account of the presence of suckers and 
 hooks. The various muscle-groups of the body can be followed a 
 considerable distance through the "neck," but their arrangement varies 
 very much according to the nature of the attaching apparatus. We 
 will now simply refer to the detailed description which we shall 
 afterwards give of the head both in Tcenia and in Bothrioceplialus, 
 and will only note that these two types do not by any means exhaust 
 the existing modifications. 
 
THE NERVOUS SYSTEM. 
 
 295 
 
 The musculature of the head is not always limited to the hitherto 
 discussed groups of fibres. Special, more or less complex, muscular 
 arrangements are brought into requisition for moving 
 the suckers, and also sometimes the hooks, as in 
 Tcenia. The most peculiar modifications are found 
 in Tcenia (Fig. 151) and TetrarhyncJius, in which not 
 only have the suckers a specially strong and complex 
 musculature, but the hooks are seated on a more or 
 less proboscis-like muscular apparatus (four of which 
 are present in TdrarJiynchus), which finds a parallel 
 only in the Acanthocephali. 
 
 Similarly, there are usually special muscles in 
 connection with the penis, to which we shall after- 
 wards return. 
 
 The Nervous System. When we consider the 
 development of the muscles, it seems strange that 
 the nervous system has long been sought for in vain. 
 It is true that some investigators have described a 
 central ganglion in the head of certain species, and 
 especially in Tetrarhynchus, which is distinguished 
 by the large size of that part of the body. I recall 
 especially the observations of J. Miiller and Wagener, F IG i5i._Longi- 
 but they have still left us without any real proof of tudinal section of 
 
 ,1 i> ji j_- mi A\ a young Tcenia 
 
 the correctness of their representations. Ihus, the serrata, consisting 
 existence of a nervous system in the Cestodes long mainl y of head and 
 remained a moot-point, and that the more naturally 
 since the reports as to the nature of the ganglionic apparatus contra- 
 dicted one another, and the great majority of observers had to declare 
 themselves unable to find anything which could be with certainty 
 denoted as a nervous system. 
 
 And yet the Cestodes do possess a nervous system, and a well 
 developed one, with a central part lying inside the head, and with two 
 distinct lateral cords which run continuously down the whole chain of 
 joints, and which sometimes, as in the larger species of Tcenia and 
 Tdrarliynchus, break up into several strands running side by side. 
 In Tcenia they lie outside the excretory canals, and are easily 
 detected in transverse sections. That they have hitherto been generally 
 overlooked is largely due to the fact that they are destitute of any 
 independent sheath, and consist of but slightly specialised tissue. 
 They have not, of course, remained wholly unobserved. For not only 
 was the cephalic ganglion described by the older observers in Tetra- 
 rliynckus, partly at least, as really related to the nervous system, 1 
 
 1 See especially Wagener's representation, " Entwickelung der Cestoden," Den 
 naturk. Verhandl. Holland. Maatschappy : Haarlem, pi. iv., 1857. 
 
296 THE ANATOMY OF CESTODES. 
 
 but the same must be said of the " plasmatic longitudinal vessels," 
 described by Sommer and Landois, and referred by them to the ali- 
 mentary system. 1 Similarly Botticher described the cephalic ganglion 
 of Bothriocephalus latus as an anastomosis of excretory vessels, 2 and 
 I have myself regarded the lateral nerves of B. cordatus as of a 
 vascular nature. 3 
 
 Schneider was the first to identify these structures as nerves, 
 and observed a wide anastomosis formed by them in the head of 
 Ligula and Tcenia perfoliata. His identification was not based so 
 much on their liistological structure as upon their anatomical resem- 
 blance to the nervous system of Nemertines. The resemblance in- 
 cludes among other points this, that in both Tcenia perfoliata and the 
 Nemertines the nerve cords are lined with cells towards their ventral 
 and dorsal surfaces. SchiefFerdecker has supported Schneider's con- 
 clusion, trusting mainly to the results of a histological investigation, 
 according to which the so-called " vessels " are resolved into spongy 
 tracts, consisting of fibrils with layers of very delicate fragile cells. 
 Schiefferdecker believes further that he has found peripheral nerve 
 endings, both on the muscular fibres, where they have the form of the 
 so-called "terminal triangles," and also as independent structures, 
 something like Pacinian bodies (O011-0'017 mm. long by 0'004-0-006 
 mm. broad) distributed through the body-parenchyma of T. solium, 
 T. clliptica, and especially abundant between the thick fibrous bundles 
 of the musculi transversales. 
 
 The almost contemporaneous researches of Blumberg* and Steu- 
 dener, and the essentially corroboratory results of my pupil Kahane, 
 with which my own observations lead me to concur, may be held as 
 
 decisive as to the presence and general 
 nature of the nervous system. 6 
 
 The cephalic ganglionic mass con- 
 sists of a tolerably thick transverse 
 band, which in Tcenia lies somewhat 
 deep below the proboscis or so-called 
 
 FIG. 152. Nervous system of Tcenia " rOStellum," but which in BothriO- 
 
 perfoliata. (x 20.) cephalus and Tetrarhynchus is some- 
 
 what approximated to the upper surface of the head. The ends of 
 
 1 In Tcenia these strands were erroneously described as simple canals, and as lying in 
 the inside of the excretory vessels ; Zeitxchr. f. uriss. Zool., Bd. xxiv., p. 515, note, 1874 ; 
 see Nitsche, ibid., Bd. xxiii., p. 191, 1873. 
 
 2 Archivf. pathol. Ansit., Bd. xxx., p. 109, 1864. 
 
 3 First German edition of this work, Bd. i., p. 445. 
 
 4 " Ein Beitrag zur Anatomic der Taenia plicata, T. perfoliata und T. mamillana," 
 Archivf. wits. u. pract. Tkierheilk., Bd. i., p. 23, 1877. 
 
 5 [See also the later investigations of Pintner, " Untersuchungen iiber den Ban des 
 Bamlwurmkorpers," pp. 67, et seq. : Wien, 1880. R. L.] 
 
HISTOLOGY OF THE NERVOUS SYSTEM. 297 
 
 this nervous mass, corresponding to the sides of the head, are usually 
 thicker than the band stretching between them, though we are not 
 warranted by the histology in regarding them as two ganglia united 
 by a commissure, as Blumberg 1 and others have done. A strong 
 nerve cord runs backwards from each of these lateral swellings, and 
 since they are almost as broad as the latter, they look like direct 
 prolongations. Each passes outwards in a curved course, and, enter- 
 ing the body, becomes one of the above-mentioned lateral nerves 
 which run down the middle layer close by the border, 2 to which they 
 sometimes send an external branch. Such is the case in Toenia 
 perfoliata, where also one can observe, opposite the origin of the 
 lateral nerves, another branch, which runs forward between the 
 suckers, evidently designed to supply the head. 
 
 It is difficult to analyse the histological structure of these nerves, 
 and the accounts of their nature vary widely. In Toenia perfoliata I can 
 recognise, like Kahane, a distinctly fibrous texture in the finely granular 
 clear mass of the cephalic ganglion, and also lying between the fibres, 
 numerous small (0 '01 5-0*02 5 mm.) ganglion cells with a nucleus, and 
 membraneless, granular protoplasm. These are to be found both in the 
 median commissure and in the lateral swellings, and have usually an 
 oval or triangular form, which is probably to be regarded as related to 
 the presence of fibrous processes, especially since the long diameter of 
 the cell is always in a line with the direction of the fibres. Although 
 these cells are by no means sparsely distributed through the ganglion 
 mass, I cannot at all agree with Blumberg in regarding the latter as 
 merely a conglomerate of ganglion cells. In Steudener's preparations 
 the cells had fallen into pieces, and their presence was only indicated 
 by the " somewhat large round nuclei with nucleoli " which remained. 
 
 The histological analysis is rendered more difficult by the fact 
 that the nerve substance is penetrated throughout by a fine meshwork 
 of supporting tissue, which is not striking in Tccnia perfoliata, but is 
 in some other cases strongly developed (in Tcenia crassicollis, accord- 
 ing to Steudener). This meshwork is also found in the lateral nerves, 
 where it sometimes predominates so much over the fibres that the 
 early observers spoke of it as "spongy cords." Here and there 
 Kahane and I have both been able to detect distinct cellular struc- 
 tures; but, on the other hand, I have never been able to discover the 
 
 1 Blumberg shows (loc. cit. Tab. i., Fig. 1), besides the two main masses, also a third 
 in the sagittal space between the suckers, and speaks in the text of several aggregations of 
 ganglion cells connected by nerve filaments. 
 
 2 We have already noted how Sommer erroneously places the lateral nervous cords of 
 Ticnia saginata inside the longitudinal vessels ; Zeitschr. /. wlss. Zool., Bd. xxiv., Tab. xliii. 
 and xliv., 1874. 
 
298 THE ANATOMY OF CESTODES. 
 
 layer of cells which Schneider described as lying on the dorsal and 
 ventral surface. 
 
 The Alimentary System. We have already noted how the struc- 
 ture of the Cestodes is simplified by the absence of these organs. Nor 
 is it the alimentary canal alone which is wanting, but blood-vessels 
 and blood are also sought for in vain. The transference of the nutritive 
 fluid is wholly effected by osmosis as in the other bloodless animals, 
 which include a great many of the parenchymatous worms. 
 
 Attempts have, indeed, been made to credit the Cestodes with 
 these structures. It used to be very common to describe an alimen- 
 tary canal, and even a two-lobed one, as in the majority of the Trema- 
 todes. Observers spoke of two vascular canals running laterally 
 throughout the whole chain, and opening to the exterior, sometimes 
 on the top of the head, sometimes by the suckers. Longitudinal 
 canals the Cestodes certainly do possess, which run uninterruptedly 
 from head to terminal joint, and which are sometimes straight, or 
 sometimes bent into zigzag folds, according to the state of contrac- 
 tion exhibited by the animal. But these canals are not alimen- 
 tary ; they have no mouth opening to the exterior ; they contain no 
 chyme, but only a clear watery fluid, without granules, and at most 
 yielding a finely granular precipitate on treatment with certain re- 
 agents (absolute alcohol). This substance is occasionally expelled in 
 the form of little pillars of varying length. The chemical analysis of 
 these masses yields, according to Sommer, sub- 
 stances which are related to xanthin and guaniii. 
 
 The Excretory System. From what has just 
 been said, we may take it as proven that the 
 longitudinal canals of the Cestodes have an 
 excretory function, as has indeed been for long 
 very generally assumed from the analogy of the 
 Trematodes. x 
 
 The arrangement of the vessels is not the 
 same in all the Cestodes, nor are they typically 
 two, but rather four in number, particularly in 
 , . forms with four suckers. Four are generally to be 
 
 FIG. 153. Head of > . . J 
 
 Twnia term/a, with its seen in the head, corresponding in position to the 
 excretory vessels ( x 24). suc k erS) an( j urnting under the rostellum, when 
 there is one, by means of a simple or plexifonn circular vessel. 
 
 1 The term *' water vessels," introduced by v. Siebold to denote these canals, is by 
 no means happy. In the first place, the contents do not consist of water, and further, 
 the name is associated with v. Siebold's erroneous idea that the "water vessels" were 
 respiratory (" Vergl. Anat.," pp. 43 and 137, 1848). Further, the term has been used to 
 denote the most diverse structures. See my remarks in Bergmann and Leuckart, " Vergl. 
 Anat. u. Physiol.," p. 284, 1851. 
 
LATERAL AND TRANSVERSE EXCRETORY VESSELS. 
 
 299 
 
 From the head the four vessels pass to the neck of the tape-worm, 
 where, with the increasing breadth, they diverge ever further from 
 one another, till they finally acquire a lateral position. 
 
 In many species these lateral stems can be followed throughout 
 the whole chain as four strands, sometimes equally developed, or 
 sometimes with one canal on either side abortive. This unequal 
 growth is seen in very various degrees, and is sometimes much 
 marked, especially in the larger Tcenice, where one canal much 
 narrower has been observed running for some distance considerably 
 to the inside of the larger (see Fig. 148), but gradually dis- 
 appearing in the broader and thicker joints. 1 Instead of the four 
 canals, there is thus but one on either side, but this has a considerable 
 diameter, which has grown in proportion to the joints. This is the 
 state of the case, e.g., in Tcenia saginata and T. solium, while T. elliptica 
 and T. perfoliata, on the other hand, are 
 instances of forms where there are two vessels 
 on either side, in the first case unequally, 
 and in the latter almost equally developed. 
 
 One must not suppose that these vessels run 
 isolated through the body of the tape-worm. 
 As in the head, so in the joints, they are con- 
 nected by a transverse anastomosis, by a 
 circular vessel, when four canals are present, 2 
 or by a simple vessel, where there are 
 only two. The anastomosis always takes 
 place at the posterior border of the joint 
 (Fig. 147), and has about the same diameter 
 as the connected vessels. 
 
 We may further note that the width of 
 the vessels is not always equal, but under- 
 goes many changes, which take place indeed 
 only slowly and gradually, but sometimes 
 are so marked as to result in the dis- 
 appearance of individual vessels. One is 
 
 FIG. 154. Joint of Tcenia 
 ccenurus, with excretory vessels 
 and generative organs. ( x 10.) 
 
 sometimes inclined to suppose with v. Siebold (in the case of Tcenia 
 cchinococcus), that the walls of the vessels possess a slight but real 
 
 1 Moniez connects the abortion of these canals, perhaps not without reason, with the 
 formation and growth of the genitalia (Bull. sci. dep. Nord, p. 225, 1878). He is, how- 
 ever, wrong in regarding the strands of Sommer, which we have seen to be nerves, as the 
 remains of the aborted vessels. Indeed, he has afterwards recognised their nervous 
 nature (ibid., p. 73, 1879). [According to Pintner's observations, the abortive vessels 
 always lie on the dorsal aspect of the body. R. L.] 
 
 a Steudener denies the existence of these circular vessels, and asserts that the com- 
 munication between the two sides is always effected by a simple cross vessel. This ia 
 a mistake, as is proved by Kahane's researches on Tcrnia pcrfoliata. 
 
300 THE ANATOMY OF CESTODES. 
 
 power of contracting, were it not, however, possible that the phenomena 
 observed were due to external pressure or to internal obstruction. At 
 any rate, the vessels even the widest of them are without circular 
 muscles. Their walls consist of a clear, structureless cuticular mem- 
 brane, which is of varying thickness, according to the width of the 
 lumen, but is otherwise without peculiarity. A coating of cells has 
 never been observed, even on the outer surface of the vessels, which is 
 on all sides in direct contact with the connective-tissue substance in 
 which they are embedded. 
 
 Here and there one can observe individual fibres attaching them- 
 selves to the walls of the vessels. The connection is effected by means 
 of a small wing-like or conical terminal piece, which is somewhat like 
 the so-called " terminal triangle " of the motor nerve fibres. I can 
 hardly doubt that these fibres have a muscular character, and that they 
 are able to affect the width of the vessels, especially since they lie at 
 right angles to the walls. If we suppose, what is indeed warranted 
 by the optical characters of the walls, that the canal system of the 
 Cestodes is in a state of elastic tension, even when the vessels are 
 moderately full, then the presence of these special dilators is very 
 natural, and well suited to increase or to oppose the action of obstruc- 
 tion or pressure, as the case may be. The local limitation of these 
 actions is readily intelligible, since the contents of the vessels can 
 only move backwards, in spite of the continuity of the whole system. 
 It has never been found possible to fill the longitudinal stems by in- 
 jecting substances from behind forwards, while there is no difficulty in 
 driving the fluid from the head downwards through a long stretch of 
 joints. This is explained by the presence of a valvular arrange- 
 ment, which is formed (according to Platner and Sommer) by two 
 opposite folds or duplicatures of the walls, which project into the 
 lumen at a point above the transverse anastomoses. 
 
 This arrangement would of course result in a constant accumula- 
 tion of excreted matter in the posterior joints, were there not some 
 means for its removal. And so there is, for at the end of the last 
 joint the vascular apparatus opens to the exterior. 
 
 This is generally effected by means of the transverse anastomoses. 
 In the posterior joints which are sharply divided from one another, the 
 transverse branches shorten according to the depth of the constriction, 
 and finally, when the joints separate and the vessels rupture, the line of 
 anastomosis becomes a cross cleft. This has no great length, and, 
 curving forward, assumes a sort of bladder-like form, while the line of 
 rupture is at the same time drawn together. It is this bladder which 
 receives the longitudinal vessels and conducts their contents to the 
 exterior, for which function it is specially fitted by the presence of the 
 
11AMIFICATION OF THE EXCKETORY VESSELS. 301 
 
 circular muscles of the body which surround it, and are thus able to 
 cause it to contract. 1 
 
 What I have said above as to the excretory apparatus of the Ces- 
 todes is primarily applicable only to those species with four suckers. 
 In Bothrioceplialus, which has only two suctorial grooves on the surface 
 of the head, the structure of the canals is somewhat different, since the 
 longitudinal canals are not only increased in number, but are very 
 thoroughly connected by numerous transverse and oblique anastomoses, 
 which are" quite independent of the joints and 
 form a more or less close mesh work. Usually 
 there are eight of these longitudinal vessels, 
 which are equally distributed on either side, but 
 there are cases where sixteen and even more ap- 
 pear, though not all necessarily of the same size. 
 Towards the head, these canals usually run to- 
 gether till only two main stems are left. It is 
 doubtful whether these are united in a loop, as 
 in Tcenia, but in some species at least this is 
 not so. At the posterior end one finds a FIG. 155. Excretory ap- 
 
 r paratus of Bothnoccphalus 
 
 distinct opening in the form of a bowl or probostideus, after Steu- 
 bladder-like depression into which the longi- dener - ( x 32 -) 
 tudinal canals run. This structure is most conspicuous and inde- 
 pendent in Caryopliyllceus, which, as is well known, has no joints, 
 and in which, therefore, the posterior extremity is permanent. It has 
 formed a longish tube, which exhibits a distinct pulsation effected by 
 the musculature investing its cuticle. 2 
 
 The above-mentioned network of vessels is not the only structure 
 of the kind to be found in Botliriocephalus. In small transparent 
 worms, which can readily be investigated alive, one can convince 
 oneself of the existence of a system of fine, richly ramified and 
 
 1 Wagener describes special excretory openings in the anterior end of many Cestodes 
 (" Entwickelung d. Cestoden," Breslau, 1854: Nova Acta Cces.-Lcop. Acad., Bd. xxiv., 
 Suppl. ), which are connected with the longitudinal vessels by short cross branches. Both 
 Kolliker and I think we have occasionally observed these openings. Hoffman has lately 
 described similar openings in Tetrarhyncltus, not, however, behind the suckers, but before 
 them, and in fewer numbers also on the anterior lateral borders ("Ueber den encys- 
 tirfcen Scolex von Tetrarhynchus," Niederldnd. Archiv f. Naturw., Bd. v., Heft. L, p. 1, 
 1879). [The investigations of Fraipont (Archiv. d. BioL, t. ii , p. 10, 1881) have shown 
 that such secondary openings are by no means uncommon in tape-worms. In Ligula, 
 where Riehm (Corresp.-BL d. Natunc. Ver. f. Sachsen u. Thiiringen, p. 276, 1882) observed 
 them, they were arranged in regular metameric fashion. Pintner (loc. cit., p. 31), in con- 
 tradiction to the above, remarks that the longitudinal vessels always open singly at the 
 hinder margin of the joints. R. L.] 
 
 2 According to Steudener, this funnel-shaped organ is, even in the case of Caryophyl- 
 I&us, only a depression of the posterior extremity. 
 
302 THE ANATOMY OF CESTODES. 
 
 interlaced vessels, lying in the more superficial parenchyma, and 
 partly close under the cuticle. Though not uniformly developed, 
 these vessels are distributed over the whole body, and are connected 
 so frequently and distinctly with the larger stems as to leave 
 no doubt as to the relations of the two systems. The finer vessels 
 obviously form the proper excretory apparatus, being suited to act 
 as simple filters by the structureless nature of their walls, whilst the 
 coarser canals are the efferent ducts. Here and there, doubtless, sub- 
 sidiary functions are discharged ; for example, the abundant develop- 
 ment of the fine network, in the head especially, in forms with com- 
 plex suctorial organs, leads one to conjecture that they act as a sort of 
 corpora cavernosa in the expansion of the suckers. 
 
 As in Bothriocephalus so is it in the other tape-worms, even in 
 Tcenia, as one can observe in fresh clear specimens of say Tcenia 
 elliptica. It is not, indeed, always possible to follow the capillary 
 system for a long distance without interruption, since the individual 
 vessels often seem to disappear and crop up again at other places. 
 Nor are their relations to the longitudinal canals equally distinct 
 throughout. * 
 
 What specially attracts the attention of the observer to this peri- 
 pheral apparatus, is the presence of small, continually waving, cilia- 
 like lappets which are situated on the inner wall of the vessels, 
 especially at the clefts, and which serve to keep up a continuous 
 movement of the fluid, independent of the contractions of the body. 
 In suitable specimens, such as Tcenia elliptica, and especially in 
 Tricenoplwrus, it is not difficult, with a little careful observation and 
 with a high power, to detect these cilia-like lappets, 2 and they have 
 been noticed by v. Siebold. M. Schultze, and others. Their existence 
 has, however, been lately called in question, especially by Steudener. 
 The cause of this mistaken criticism is to be found mainly in the 
 too exclusive examination of sections instead of living animals, and 
 also doubtless in the use of large opaque tape-worms, which, though 
 more readily obtainable for examination, are but little suited for 
 deciding the point in question. 
 
 But not only did the cilia-like apparatus escape observation, but 
 even the capillary vessels in which the former are situated. Longi- 
 tudinal stems and anastomoses were held to represent the whole excre- 
 
 1 It is a striking fact in this connection that the peripheral network cannot be in- 
 jected by way of the longitudinal vessels. This is perhaps due to the existence of valves 
 similar to those at the entrance of the cross vessels. We cannot, however, immediately 
 conclude that there is no communication between the systems. 
 
 2 The discovery of these structures is due to G. Wagener, who has alto earned our 
 approbation by the demonstration of the above-described capillary excretory system ; 
 see " Entwickelung d. Cestoden," loc. cit., p. 14. 
 
PLASMATIC VESSELS OF SOMMER AND LANDOIS. 303 
 
 tory system ; no ramifying side branches were to be seen ; at most a 
 few accessory branches have been described in the head, and the 
 suckers are indeed provided (Fig. 153) with a special vessel springing 
 from the above-described circular commissure. 
 
 It is also true that now and then vessels are given off from the 
 longitudinal canals, and are sometimes hardly less important than those 
 just mentioned. This is the case, for instance, in Tcenia perfoliata, 
 as was noted even by Kahane. The vessels pass soon after their 
 origin into the cortical layer, where they ramify, and finally assume a 
 capillary character. 1 The " plasmatic vascular system " observed by 
 Sommer and Landois in Bothriocephalus latus, traces of which are also 
 found in Tcenia saginata, obviously belongs to this capillary system. 
 This, however, only refers to those vessels which pass under the so- 
 called " subcuticula," and are really vessels, for in his later work on 
 Tcenia saginata Sommer has evidently represented the lateral nerves as 
 part of this apparatus. The vessels are described as fine and very 
 thin-walled passages, which ramify peripherally as well as cen- 
 trally, and ultimately become united with the processes of connec- 
 tive tissue corpuscles. By means of these cells, and by means of some 
 of the pores of the cuticle, they come into communication even 
 with the external layer. An excretory apparatus, consisting of 
 wider canals, was observed by Knoch 2 and Botticher, 3 in young and 
 transparent living examples of Bothriocephalus latus, but its existence 
 has since been denied. 
 
 The designation chosen by Sommer and Landois for the vascular 
 system which they have observed, and the description there given, leave 
 not the slightest doubt that they regard the canals in question as an 
 arrangement for nutritive purposes. This idea is thus a repetition, 
 although in improved form, of an opinion, which we have formerly 
 maintained, and still maintain, to be erroneous, although it has mean- 
 while found a representative in Blumberg. 4 It is true that, according 
 to the latter, it is not the whole of the surface of the body that serves 
 for the reception of nourishment and for its introduction into the vas- 
 cular system, but only the inner surface of the suckers, whose cuti- 
 cular pores are in connection with the spreading terminal processes of 
 the longitudinal canals. " The vessels form, especially at the base of 
 
 1 [According to the observations published by Pintner and Fraipont, in the above- 
 mentioned memoirs, the behaviour of this capillary apparatus is very different from that 
 here described. Its tubes never form a network, but, singly or united in pairs, open into 
 the wider canals, and bear each a ciliated funnel at the outer end. The cilia like 
 lappets are never present in the interior of the tubes. K. L.] 
 
 - Mem. Acad. imper. St. Petersbourg, t. v., No. 5, PI. ii., p. 38-38, 1862. 
 
 a Archivf. pathol. Anat., Bd. xlvii., p. 370, 1869. 
 
 4 Loc. cit., p. 39. 
 
304 THE ANATOMY OF CESTODES. 
 
 the suckers, a regular network, which unites into larger stems as it 
 leaves the suckers. In the spaces between the suckers the vessels 
 anastomose. Here originate the longitudinal stems of the body. In 
 Tccnia perfoliata I observed only two stems, 1 one of which ran down 
 each side of the middle layer of the body. The thickness of the walls 
 is considerable. In every joint the longitudinal canals give out 
 branches, which ramify." 
 
 And it is not only fluids which find their way through the pores 
 of the suckers, but formed substances, " roundish bodies of the size of 
 blood or chyle corpuscles." These are found in the intestinal mucous 
 membrane of the host, and are probably nothing else than blood and 
 chyle corpuscles. They are very frequently found in the interior of the 
 suckers, which are sometimes quite full of them. Blumberg thinks 
 that he has also found these corpuscles in the vessels of the suckers, 
 and followed them on their way to the interior ; but I must confess that 
 I am of Kahane's opinion, who identifies these so-called corpuscles with 
 cross sections of muscles, and regards the contents of the hollow of 
 the suckers merely as epithelial cells and their remains. After all 
 this, I see no reason for renouncing the old opinion as to the vascular 
 apparatus found in the Cestodes ; and the less so since this apparatus 
 has been shown by the elder van Beneden to be most thoroughly 
 homologous with that occurring in the Trematodes, where the presence 
 of an intestine shows, more distinctly than in other cases, that it is to 
 be regarded as an excretory apparatus. 
 
 The Sexual Organs. The structures which we have been consider- 
 ing extend throughout the whole body of the tape-worm, although the 
 various parts may exhibit many differences in the nature and perfec- 
 tion of their development. But it is quite otherwise in regard to the 
 last organ which we have to describe ; the great distinction being, 
 in a word, that though common to the joints, it is completely absent 
 from the so-called " head" of the tape-worm. It is true that at first the 
 proglottides are without sexual organs. But their asexuality has only 
 a short duration. As soon as a definite size is reached, the sexual de- 
 velopment begins just as is the case in many of the lower animals. 
 The separate parts originate in definite succession, they grow, they 
 perform their functions, and ultimately attain so large a size that 
 the other organs of the Cestode body are quite dwarfed. The 
 uterus is developed most of all, and by the accumulation of 
 the hard-shelled ova it assumes a more or less brownish colour, 
 and renders the appearance of the otherwise peculiar mature 
 joints very striking. This is especially true of the larger species, 
 
 1 This is a mistake, for four longitudinal stems Can be plainly distinguished. 
 
THE SEXUAL ORGANS. 
 
 305 
 
 such as Tcenia solium and Bothrioceplialus latus, whose branched 
 (Fig. 156) or rosette-shaped (Fig. 157) uterus was known to observers 
 as early as the beginning of the last century (since 
 Andry), although it was generally erroneously regarded 
 as an ovary until the time of v. Siebold. 1 
 
 But though the sexual organs of the tape-worms 
 are thus very striking, their accurate investigation is in- 
 volved in great difficulty. It was, of course, soon agreed 
 that the proglottides were provided with male as well as 
 female organs, but the structure and the relation of the 
 various parts eluded for a long time further deter- 
 mination. We have, however, gradually obtained a 
 satisfactory insight into these, thanks especially to the re- 
 searches of v. Siebold, Sommer and Landois, 2 and myself. 
 
 What stands in the way of the analysis of the sexual 
 apparatus of the Cestodes is partly the parenchymatous 
 nature and thickness of the tape-worm body, which 
 almost always necessitate a detailed methodical mani- 
 pulation, and partly also the complex structure and the .FIG. 156. Two 
 thick outline of the various parts. Besides this, the folium 1 ^th 
 form and structure of the latter often vary considerably branched uterus, 
 from those of nearly related species, and are influenced 
 in an unusual way by the external form of the joints, as will be still 
 more discussed in considering the Tseniadse. 3 
 
 Proceeding to the general consideration of these sexual organs, I may 
 
 FIG. 157. Female sexual organs of Bothriocephalus latus, showing the uterus, ovary, 
 shell -gland, and yolk-gland, (x 12.) 
 
 1 Concerning the historical development of our knowlege of the sexual organs of the 
 Cestodes, compare especially the statements of Sommer, Zeitschr. f. wiss. ZooL, Bd. xxiv., 
 p. 299, 1874. 
 
 2 Besides the formerly mentioned treatise on Bothriocephalus, Sommer's later work on 
 the structure and development of the sexual organs of Tcenia mediocandlata and T. solium 
 (Zeitschr. /. wiss. ZooL, Idc. cit., supra) deserves special mention. 
 
 For comparison with the original descriptions given by Sommer and myself, chiefly 
 of the common bladder- worms, I may refer to the data furnished by the following investiga- 
 
 U 
 
306 
 
 THE ANATOMY OF CESTODES. 
 
 remark, in the first place, that the male apparatus consists usually of 
 a large number of testicular sacs, whose delicate orifices open into 
 a seminal duct with cirrhus-pouch and cirrhus (penis). In the female 
 apparatus we have to distinguish not only an ovary (germarium) and 
 yolk-gland (albuminiparous gland), which co-operate in the formation 
 of the eggs, but also two kinds of exit ducts, a vagina, which serves 
 for the reception of the semen, and a uterus, which collects the 
 fertilised eggs, and often contains them until the formation of the 
 embryo. With the vagina there is often connected a receptaculum 
 seminis, and at the beginning of the uterus, where the oviducts are 
 connected with the posterior end of the vagina, there is yet another 
 special organ or shell-gland (Figs. 158 and 159). 
 
 The presence of a separate yolk-gland along with the ovary is a 
 peculiarity which the Cestodes share with numerous other flat-worms, 
 and especially with the Trematodes. The secretion furnished by the 
 gland surrounds the eggs, which in their state of formation possess 
 only a thin, clear protoplasmic sheath, and thus during the whole of 
 
 FIG. 158. Sexual organs 
 of Tcenia ccenurus. ( x 10.) 
 
 
 
 FIG. 159. Sexual organs of Both- 
 riocephalus latus (from the ventral 
 side), (x 20.) 
 
 their sojourn in the ovary exhibit conditions which in other cases exist 
 only for a short time, until the deposition of the granular yolk. Such 
 
 tors concerning the structure of the sexual organs in other forms of Tccnia Stieda (Archiv 
 f. Naturgesch., Jahrg. xxviii., p. 200, 1862), Pagenstecher (Zeitschr. f. wiss. Zool., Bd. 
 ix., p. 523, 1858), Feuereisen (ibid., Bd. xviii., p. 161, 1868), v. Linstow (Archiv f. 
 Naturgesch., Jahrg. xli., p. 187, 1875), and Kahane (loc. cit.). 
 
THE UTERUS AND VAGINA. 
 
 307 
 
 being the state of matters, we can understand how v. Siebold, to whom 
 we owe the first discovery of this peculiar structure, 1 and his next 
 followers (among whom I was numbered at the time of the first edition 
 of this work) recognised in the products of the ovary only a germinal 
 vesicle, which was then generally believed to serve, as in other animals, 
 as a starting-point for the future egg. We need hardly add that v. 
 Siebold's idea needs no particular refutation at the present day. 
 
 But the Cestodes have, in common with the Trematodes, not merely 
 a double egg-forming organ, but also a double female conducting ap- 
 paratus. The opinion formerly held that the so-called " uterus " of the 
 latter took part in copulation as well as in the deposition of the eggs, 
 was erroneous, as has since been placed beyond a doubt by the well 
 corroborated observations of Blumberg and Stieda. 2 The same error 
 prevailed, however, in regard to the female conducting apparatus of 
 Bothrioceplialm until Stieda's researches proved the existence in this 
 case also of a special vagina beside the uterus. 3 In the Tseniadae 
 the simultaneous presence of vagina and uterus had indeed been long 
 recognised, but the structure in this case seemed exceptional, since 
 in these animals the uterus is anomalous in being destitute of an 
 opening. 
 
 Minot considers the presence of two kinds of female conductive 
 canals as such a characteristic and important peculiarity that he 
 proposes to unite the Cestodes and Trematodes into one group of 
 " Vaginiferce." But, on the other hand, it ought to be remembered 
 that a similar arrangement also occurs in other lower animals. The 
 female butterfly, for instance, generally possesses a vagina, which is 
 separate from the oviduct, except for a narrow duct, and opens 
 exteriorly by a special opening near the latter a state of affairs 
 essentially similar to that found in the so-called " vaginif erous " 
 Helminths. 
 
 Although united in the same body, the male and female organs of 
 the Cestodes differ from each other, in becoming functionally capable 
 and mature at different periods of life. 
 
 As I have long since shown, it is the male organs which first 
 develop and attain maturity, and that at a time when the female 
 parts are often imperfectly sketched out, so that in many cases one 
 feels tempted (Feuereisen remarks this especially in the Tcenia 
 setigera of the goose) to characterise the anterior joints as exclusively 
 male (Fig. 160, A). In studying the male apparatus, it is therefore 
 
 1 "Lehrbuch der vergleichenden Anatomie der wirbellosen Thiere," p. 146, 1848. 
 
 " Ueber d. angebl. inneren Zusamrnenhang d. mannl. u. weibl. Organe d. Trema- 
 toden," MuUer'sArchivf. Anat. v. PhysioL, p. 31, 1871. 
 
 a " Ein Beitrag zur Anatomie des Bothriocephalus latus," ibid., p. 194, 1864. 
 
308 THE ANATOMY OF CESTODES. 
 
 better to examine the younger proglottides, whose ovaries are still 
 without eggs. In the older joints, in which copulation has taken 
 place, and the embryos are perhaps already developed, the testicular 
 sacs are generally empty and deserted, and sometimes have even in 
 great measure disappeared. Even the cirrhus and cirrhus- pouch 
 often fall into decay (Fig. 160, B). 
 
 This unequal development is most striking in the Tseniadae, which, 
 having no uterine opening, are unable to void their eggs successively, 
 and form them indeed only during a relatively short space of time, 
 whilst the Bothriada3 go on depositing during their whole life, as long 
 as they remain in the intestinal canal of their host, and thus require the 
 spermatic elements during a longer time. In this way it also becomes 
 clear that the Bothriadae not only continually replace the externally 
 deposited eggs by new batches, but as time goes on collect larger and 
 larger numbers in their uteri, which, while still in the neighbourhood 
 of their place of formation, distinctly exhibit the characteristics of 
 their youthful stage. On the contrary, the number of eggs in the 
 Tcenice is not increased after the transference has once taken place into 
 the uterus. And as this transference, as already mentioned, only lasts 
 during a definite and relatively short period, the eggs in the interior of 
 the uterus are all of nearly the same age, and of the same or only slightly 
 different development. 1 And this is all the more surprising in these 
 animals as the development of their eggs goes much further than in 
 the case of Bothriocephalus, and only terminates with the formation of 
 an embryo. When the uterus is filled, the female germ-producing 
 organs of the Tcenice have fulfilled their function, just as have the testes 
 after the filling of the seminal duct, and are then gradually destroyed 
 by the pressure of the uterus, which becomes larger and larger during 
 the embryonic development of the eggs. In the investigation of the 
 generative organs in Tcenia, the smaller " unripe" joints must evidently 
 be examined, for in the so-called " ripe " or pregnant proglottides 
 these parts are only slightly present, or have even entirely dis- 
 appeared. 
 
 1 Sommer declares (loc. cit., p. 532) my statements, that "in the case of the Tcenia; 
 the transference of the eggs into the uterus is limited to only a short space of time," 
 and that consequently "the eggs of a uterus are always of nearly the same age, and 
 of similar or only slightly different development," to be erroneous. He bases this asser- 
 tion on the fact that the transference of the egga in Tcenia sayinata takes place over a 
 stretch of 300 to 400 proglottides, and that the eggs of the older proglottides in the posterior 
 end of the uterus stem differ considerably from those found in the side branches. I have 
 known these facts from my own experience, and for a long time, but, notwithstanding, I 
 think I am able to support my statements. For Sommer overlooks that the matter in 
 question was not the nature of the Taeniadae per se, but the contrast between it and that of 
 Eothriocephalus, and I still think that this contrast was perfectly accurately and naturally 
 characterised in the way I put it. 
 
PORUS GENITALIS AND CLOACA. 309 
 
 As has already been mentioned, the male and female organs are 
 differently situated with respect to the two surfaces of the tape- worm, 
 the former belonging to the back and the other to the ventral surface. 
 Here, too, as in the position of the sexual openings, numerous and 
 striking differences appear, which at first sight are little in accord- 
 ance with the general nature of bilateral structure. This is particu- 
 larly true of the forms which have genital openings on one margin, 
 which is the case indeed in the majority of Cestodes, and especially 
 of Tetrabotkria. 
 
 What was formerly said of the genital openings in the Cestodes 
 was only true of the vaginal opening, which is the only female open- 
 ing constantly present in these animals, and is always situated near 
 the male one. 1 These two openings, which alone form what is 
 usually called the poms genitalis of the Cestodes, vary in their 
 position, but the uterine opening, when present, is always found on the 
 ventral surface, and, with the exception of a few species with double 
 uterus and double opening, lies on or near the middle line. 2 When 
 the other genital openings are also veiitrally situated, the uterine open- 
 ing lies a short distance behind them, or more rarely near them. 
 
 There are thus two openings in the porus genitalis of the Cestodes, 
 the male opening and the female vaginal opening. They lie close 
 together, and the male one is generally above. 3 The latter only 
 assumes a lateral situation in very short-jointed tape-worms, such as 
 Tcenia nana and T. perfoliata, and also in Ligula and Sckistocepkalus ; 
 and it is usually so associated with the female, that they have a short 
 and narrow pouch in common, a general cloaca, which is clad with 
 a thin prolongation of the investing cuticle, and, in spite of its origi- 
 nally small size, seems capable of considerable extension. In many 
 species, and especially in the larger ones, a more or less marked 
 swelling surrounds the porus, which is sometimes flat and plate-like, 
 but often deeper, and then protrudes like a papilla on the external 
 surface (Tcenia saginata, &c.). 
 
 From the male opening there generally protrudes a longer or 
 shorter thread-like process, which is known by the name of " cirrhus." 
 
 1 The statement of von Siebold (Vergl. Anat., p. 147), that in Tricenophorus and Tcenia 
 ocellata these openings were situated far from each other, since the vulva was found on 
 the ventral surface, but the penis on the margin, probably rests upon an error. There is, 
 indeed, no doubt that he has made a mistake in the case of Tricenophorus at least, for the 
 vagina is overlooked, and the uterine opening interpreted as a vulva. 
 
 2 It is so in Tricenophorus, whose uterine opening, according to Steudener (Abhandl. 
 naturf. GescUsch. Halle, Bd. xiii., p. 302, 1877), diverges a little towards the opposite side 
 of the peripheral porus genitalis. It is the same in the Ligulidae (see Kiessling). 
 
 8 In Tetrabothrium, van Beneden (loc. cit. ) describes the vaginal as above the cirrhus 
 pouch, but this is a mistake, as the case of Tetrarhynchus has convinced me. 
 
310 THE ANATOMY OF CESTODES. 
 
 This is a copulatory organ, which is introduced into the female open- 
 ing, 1 and indeed generally into that of the same joint (van Beneden, 
 Leuckart), and being provided with a fringe of backward-directed 
 bristles or points, is specially adapted to effect a firm union. As a 
 rule, however, this cirrhus is not an independent organ, but the more 
 or less independently developed anterior end of the so-called muscular 
 " cirrhus-pouch." This is attached to the male opening, and consists 
 of a conspicuous structure of cylindrical or ampulla-like form, which is 
 completely surrounded as far as the point mentioned by the body- 
 parenchyma, 2 with which it is also connected by retractor and pro- 
 tractor muscular fibres. In a certain sense, however, the cirrhus- 
 pouch appears to be also a part of the seminal duct ; at all events, 
 the latter appears to be in direct continuity with it. Its internal 
 cavity may be observed running along the whole length of the cirrhus 
 pouch as a distinctly marked passage, with pretty thick cuticular 
 covering; and one even feels convinced that it is only the highly 
 developed muscular wall of this passage which forms the cirrhus- 
 pouch, and that it only appears to be a special structure because the 
 other far greater part of the seminal duct is destitute of this covering. 
 But on closer examination it is soon seen that the cirrhus-pouch 
 does not consist of a simple layer of muscles, but rather of a muscular 
 external wall and of an internal mass, which is partly, it is true, X)f a 
 muscular nature, but consists principally of a clear connective sub- 
 stance. The enveloping layer exhibits fine thickly matted fibres, 
 which sometimes run circularly, or at other times with a more 
 diagonal course, crossing each other and forming a hollow muscle, 
 which is evidently able powerfully to compress the interior mass. In 
 contrast to this, the fibres of the latter have a more longitudinal 
 
 1 Sommer doubts the existence of a special copulation in the Cestodes (loc. cit. t p. 
 507), and only admits an overflowing of the seed into the vaginal opening, which might 
 easily be caused by the pressure of the body after the closure of the genital pore and the 
 shutting off of the general cloaca. This, he says, he directly observed in the case of Tcenia 
 saginata and T. solium. In answer to this, I can only repeat that I have observed just as 
 directly, and in the most distinct manner, an " immissio penit" (Fig. 165) in Tcenia. cchino- 
 coccw*, and that under circumstances which excluded the possibility of confusing it with the 
 overflowing of spermatic masses. Besides this, it cannot be admitted that an organ, which in 
 many species is as long as half the width of the body, and which most obviously possesses 
 all the characteristics of a copulatory organ, should only serve its possessor as an orna- 
 ment. Yet, as the structure of the cirrhus exhibits many varieties, it is quite conceiv- 
 able and possible that the act of copulation is not always effected in the same way. But 
 the above observations of van Beneden and myself are not the only ones which can be 
 adduced against Sommer. Pagenstecher (loc. cit., p. 528) has also observed the copula- 
 tion in Tetrabothrium auricula, but in this case no self-fertilisation took place, but the 
 penis of one joint was sunk into the vagina of another, a few joints distant. 
 
 2 Kahane describes the cirrhus of Tcenia perfoliata as a special organ, situated at the 
 base of a pocket or bell-shaped cirrhus-pouch, from which it protrudes. 
 
THE CIRRHUS AND ITS MUSCLES. 311 
 
 course, for they proceed from the rounded posterior end of the pouch, 
 and, converging anteriorly, attach themselves ultimately to the cuti- 
 cular wall of the seminal duct. In many cases this anterior part of 
 the seminal duct is also characterised by a thinner or thicker fringe 
 of spines situated on the cuticle. Its course is also always straight 
 and extended, while that of the posterior part, situated at the base of 
 the cirrhus -pouch, is generally coiled or twisted. 
 
 There can be no doubt as to the purpose of this muscular terminal 
 apparatus. It serves to protrude the penis, which in the state of rest 
 is more or less withdrawn, and lengthens it by the evagination of the 
 anterior end of the seminal duct. Under the pressure of the power- 
 fully contracting muscular pouch, the internal elastic mass reacts on 
 the free and pliant anterior end, until a regular prolapsus results, in 
 consequence of which the spinous fringe of the seminal ducts emerges, 
 and its windings adapt themselves more or less to the length of the 
 prolapsus. The retraction is accomplished by the above- described 
 longitudinal fibres, which pass through the interior mass, and are 
 physiologically antagonistic to the hollow peripheral muscle. 
 
 The seminal duct, or vas deferens, proceeding from the rounded 
 posterior end of the cirrhus-pouch is destitute of special musculature. 
 Its walls consist of a thin and extensible glassy membrane, which is 
 a continuation of the above-mentioned firm cuticle, and lies loose in 
 the substance of the body-parenchyma. On the exterior there is 
 generally distinguishable a layer of clear, delicate nucleated cells, 
 which may be interpreted as a kind of epithelium, and which, so far 
 as one can judge from appearances, can hardly be referred to the con- 
 nective-tissue corpuscles. We shall consider this afterwards, when 
 describing the manner of development of the generative organs. 
 
 In spite of the thinness of its walls, the seminal duct is in many 
 cases of considerable width sometimes throughout its whole length, 
 
 .--; 
 
 FIG. 160. Two proglottides of Tcenia setigera from the goose (after Feuereisen). 
 A, Male, and B, Female development, a, end of the vagina; 6, receptaculum 
 seminis ; c, yolk-gland ; d, ovary ; / and g, seminal vesicles ; h, testes. 
 (x about 40.) 
 
 and sometimes only in a definite place in the neighbourhood of the 
 cirrhus-pouch. This is due to its contents, the spermatozoa, which 
 accumulate in it in great numbers at the time of the male maturity, 
 
312 THE ANATOMY OF CESTODES. 
 
 and distend it to such an extent that one is tempted to speak of 
 distinct sperm sacs. Sometimes straightly extended, and sometimes 
 more or less tightly wound, the canal runs in a transverse direction 
 (Fig. 158), or perpendicularly downwards (Fig. 159), according to the 
 position of the porus genitalis, and ultimately breaks up into a number 
 of thin, delicate canals, which sooner or later, and often after repeated 
 ramification, meet the little testes, and are united with them. 
 
 The anatomical condition of these vasa efferentia is largely deter- 
 mined by the distribution and number of the testes, both which factors 
 are subject to extraordinary variations. In the larger species many 
 hundred testes (Fig. 158) are found, consisting of clear and round 
 little bladders. These are each surrounded by a clear, structureless, 
 glassy membrane, 1 and contain tufts of spermatozoa, or the cells in 
 which these are formed, in different stages of development, 2 and are 
 pretty equally distributed over the whole joint. But as the size 
 diminishes, so does the number of the testicles. Instead of a hundred, 
 perhaps only some dozens are then found, as in Tcenia perfoliata 
 (Fig. 162, A), where they are situated in what 
 appear to be two rows upon the vas deferens 
 behind the sperm sacs ; or they may be reduced 
 to smaller numbers, even down to two or three, 
 as is especially the case in certain Teenies of 
 birds, such as T. setigera (Fig. 160, A), and also in 
 Fio. 161. Generative T. uncinata of the shrew-mouse (Fig. 161). 
 
 organs of Tcenia uncinata ml , . 0,1 i j TI 
 
 (after Stieda), showing The emptying of the testes is effected, like 
 receptacuium (6), germ- that of the vas deferens, by means of the 
 
 eland id), yolk-gland (c), , (.,11-11 ,1 
 
 testes (A), and cirrhus- muscles of the body, but the two processes are 
 pouch (/). ( x 25.) apparently accomplished by different groups. 
 
 While the testes are principally subjected to the pressure of the 
 transverse and sagittal fibres, which run through the surrounding 
 tissue, all the more abundantly, since this is converted into a cubical 
 meshwork by the formation of the above organs, it appears to be 
 mainly the longitudinal and transverse fibres which act upon the vas 
 deferens, and discharge its contents into the cirrhus-pouch. 
 
 1 While this glassy membrane originates in the structureless connective tissue, the 
 spermatozoa are produced by a metamorphosis of cells, which in no way differ from the 
 young connective -tissue cells. In other words, the testes, like the other viscera of these 
 animals, are only differentiations of the body - parenchyma (mesoderm). Thus we can 
 understand the statement of Moniez (Butt. Scient. dep. Nord, p. 221, 1878) that the 
 formation of the spermatic elements takes place in the meshes of the body-parenchyma, 
 and not in a special organ. In the same way, he denies the presence of special vasa 
 efferentia, and thinks that the spermatozoa make their own way through clefts previously 
 formed in the tissue. 
 
 a Moniez has made the structure of these spermatozoa the subject of special investiga- 
 tion, I'lnstitut, July 1878. 
 
THE FEMALE SEXUAL ORGANS. 
 
 313 
 
 As has been sufficiently shown by the foregoing remarks, the 
 differences in the male apparatus are of entirely subordinate import, 
 especially in so far as they are determined by the form and size of the 
 proglottides. But it is in this respect quite different with the female 
 parts, which, although also much affected in form and arrangement by 
 the above factors, exhibit, besides, other important characteristics. 
 These consist mainly in the structure of the yolk-gland, and are of so 
 fundamental a nature that we have to distinguish two types of it 
 one which occurs in the Tseniadse, and another in the remaining tape- 
 worms (Bothriadae). As both have their representatives among the 
 human Cestodes, we shall now shortly consider them. 
 
 One of these types represented in the Tseniadse is mainly char- 
 acterised by the absence of the uterine opening, and by the small 
 development of the yolk-gland, characteristics which have a certain 
 connection with each other, since they both find their explanation in 
 the above-noted peculiarities of the breeding. The vagina, which, as 
 we have seen, is separate from the uterus, appears as a distinctly 
 marked narrow canal, which extends in a transverse direction from the 
 generally marginal porus genitalis (Fig. 162), and has either a straight 
 
 FIG. 162. Sexual organs of Tcenia perfoliata of the horse (after Kahane). 
 A, Joint in male maturity ; above, cirrhus, vas deferens with sessile testes ; 
 below, the yolk-glands, uterus with shell-gland and yolk-gland, vagina with 
 receptaculum. B, Female organs at the time of the transference of the 
 eggs into the ovar}'. ( x 15.) 
 
 course, or, as in the Tcenice with extended joints (Fig. 165), curves 
 backwards towards the middle of the joint. The posterior end enlarges 
 into a receptaculum seminis of varying and sometimes considerable 
 size, and is filled with semen at a time when the uterus contains 
 as yet no eggs. The vagina itself is, on the contrary, generally empty, 
 and its lumen is much contracted, obviously because the firm cuticle 
 which covers it, especially in the posterior part, is very elastic, and 
 quickly forces the introduced semen into the receptaculum. There is 
 no muscular sheath in the vagina. The only layer found on the 
 cuticle consists of a pretty thick epithelial layer, somewhat like 
 that which we observed in the vas deferens. 
 
 But the posterior end of the vagina not only leads into a sperm 
 
314 
 
 THE ANATOMY OF CESTODES. 
 
 sac (Fig. 163, c), but is in more or less direct connection with the 
 uterus. As a rule, and perhaps always (especi- 
 ally in the case of the Cystotcenice), this union 
 is effected by means of a special tube which I 
 have named the " fertilising canal " (Befruch- 
 tungscanal). 1 It originates from the posterior 
 end of the sperm sac being indeed in some 
 measure a continuation of it and of the vagina 
 and opens into the uterus after a short 
 course. Where the latter occupies the middle 
 line, it always opens at the posterior end, where 
 the " fertilising canal/' especially in the Cysto- 
 tcenice, often assumes a curved course. At 
 the point of union with the uterus there is 
 found a small round body, consisting of 
 numerous unicellular glands, which from its 
 function I have named the " shell-gland." 
 On its way to the shell-gland the fertilising canal receives the 
 
 exit canal of the ovaries, of which two are always present in the 
 
 FIG. 163. Connection be- 
 tween the different parts of 
 the female generative appa- 
 ratus in Tcenia ccenurus. 
 o, yolk passage ; b, oviduct ; 
 f, vagina with receptaculum ; 
 d, uterus ; , fertilising canal. 
 ( x 50.) 
 
 FIG. 164. Sexual organs of Tcenia echino- 
 coccus (penis during copulation). ( x 100.) 
 
 FIG. 165. Sexual organs of Tcenia 
 ccenurus. ( x 10.) 
 
 Taeniadae. In the majority of cases these have the appearance of 
 two wing-like or hand-shaped organs, which are situated about the 
 
 1 I may take this opportunity of mentioning that I was the first to observe the con- 
 nection between the different parts of the female sexual apparatus. The description given 
 
THE SHELL-GLAND AND YOLK-GLAND. 315 
 
 the height of the sperm sac, and also somewhat below it, on the right 
 and left of the middle line, and may be beautifully and distinctly brought 
 out by injected microscopic preparations. Constructed on the type of 
 the tubular glands, they consist, especially in the larger species, of nume- 
 rous more or less branched tubes, which contain the egg- cells enveloped 
 within an extremely fine structureless membrane, in the form of clear, 
 membraneless, little balls, with comparatively large germinal vesicles. 
 
 But it is quite different with the yolk-gland (albuminous gland, 
 Sommer), not only because, although usually an unpaired organ, it is 
 sometimes drawn out to the side, but because its efferent canal opens 
 directly into the shell-gland, into which there are also poured semen 
 (Figs. 163, 164), eggs from the ovary, yolk, and shell material, and 
 which possesses all the conditions necessary for the later formation 
 of the eggs. The yolk -gland is situated near the posterior extremity of 
 the joint, and thus below the other parts of the female apparatus. In 
 the larger species it consists of a branched glandular body like the ovary ; 
 but in other cases it is of a simpler saccular shape. The very fine and 
 structureless walls enclose little cells, which in the young joints often 
 contain several nuclei, but which afterwards generally dissolve, and as- 
 sume the appearance of a somewhat thick and tough glandular secretion. 
 
 The manner in which the position and arrangement of the above 
 shortly described organs is affected by the form of the joint is well 
 shown in the structure of Tcenia perfoliata, which we may regard as 
 typical representative of the short and broad-jointed Taeniadse. It is 
 most noticeable in the ovaries, which, in contrast to their usual struc- 
 ture, appear as two thin canals, which run out from the middle line 
 towards the edges, and are provided throughout with short unbranched 
 
 FIG. 166. Male and female organs of Tcenia perfoliata (after Kahane). ( x 15.) 
 
 egg-follicles (Fig. 166). They have thus a remarkable resemblance to 
 the male secretory apparatus, which is also determined by the form of 
 the body, and runs in the same direction, and to pretty nearly the 
 
 in the former edition of this work is also the first complete analysis of these structures. 
 All the more do I regret that, in opposition to the former correct opinion held by von 
 Siebold, van Beneden, and myself (" Blasenbandwurmer," p. 79), I unfortunately repre- 
 sented the yolk-gland as the ovary, and described the real germ-gland as the yolk-gland. 
 To any one who knows the difficulties which the investigator encounters at this very part, 
 the mistake will appeat pardonable. It is all the more easily committed, since the con- 
 tents of the two glands have often a great resemblance. Further, later observers, and 
 particularly Stieda, Feuereisen, and v. Linstow, have made the same mistake. 
 
316 
 
 THE ANATOMY OF CESTODES. 
 
 same height, but does not, like the ovaries, approach the ventral, 
 but the dorsal surface. 
 
 Lastly, as regards the uterus, it is at first, in the Tgeniadae, a 
 simple and straight canal, which, according to the form of the body, 
 runs in a transverse or perpendicular direction, and in the latter case 
 its posterior end (or its middle, as in Tcenia perfoliata, Fig. 162, B) 
 is connected with the vaginal canal. Like the other portions of the 
 female apparatus, it consists of a structureless, expansible, and elastic 
 membrane, whose external surface exhibits the repeatedly mentioned 
 but here specially abundant accumulated cells. Since there is also 
 no appearance of any special muscular covering in the uterus, the 
 expulsion of the eggs through the previously formed rupture must, 
 of course, be effected by the pressure of the muscles of the body. 
 
 But afterwards, when the eggs are transferred into it, and accumu- 
 late in it in ever larger numbers, and of increasing size during the 
 
 FIG. 167. Proglottides of Tcenia nana at maturity ( x 100). 
 
 FIG. 168. Mature joint of Tcenia perfoliata with uterus ( x 10). 
 
 development of the embryo, this primitive form of the uterus undergoes 
 a continuous and often very striking change. In some cases it consists 
 
 of a simple enlargement, often so ex- 
 tensive that the original linear tube 
 becomes a bulging sac (Fig. 167), and 
 in other cases lateral processes, vary- 
 ing in number and width (Fig. 168), 
 are formed, which ultimately turn into 
 slender and often branching twigs (Fig. 
 169). But such differences, however 
 highly characteristic of the different 
 groups and species, can only be shortly 
 noted. Therefore I shall only observe 
 that in some cases the uterus even 
 breaks up into many round vesicles, containing a larger or smaller 
 
 FIG. 169. Joint of T. saginata 
 
SECOND TYPE OF SEXUAL ORGANS. 317 
 
 number of eggs. The latter are further generally enclosed in a 
 common more or less firm envelope, as we shall afterwards see in the 
 case of Tcenia elliptica and others. 
 
 If, however, there be two pori genitales in every joint, the uterus 
 always remains simple, but instead of a simple vagina, it then possesses 
 two (each with a receptaculum). In Tcenia elliptica (Fig. 143), T. 
 denticulata, and others, each vagina has a special germ-producing organ, 
 whilst in the " biporous " proglottides of Tcenia solium the ovary and 
 yolk-gland are developed as usual along with two symmetrical vaginse 
 (p. 279). According to Moniez, the two receptacula of T. Giardi (a new 
 form found in the intestine of the sheep, and nearly related to T. denticu- 
 lata) send each a fertilising canal to the ovary of the opposite side. 1 
 
 The second typical form of the sexual organs is much more widely 
 distributed among the Cestodes than the one which we have considered, 
 and indeed apparently occurs in all the species which remain after 
 the exclusion of the Tseniadse (i.e., in the Bothriadae), being found in 
 the forms where the genital pore is marginal, as well as in those where 
 it is situated on the surface. As the former have a very general re- 
 semblance to the Tcenice in regard to the structure of the male appar- 
 atus, vagina, and ovary, and as none of them are found in man, we 
 need not give them special attention. 2 Further, their distinctive 
 characteristics, and especially the structure of the yolk-gland and the 
 presence of a special uterine opening, 3 will be sufficiently elucidated 
 
 1 Comptes rendus, t. Ixxxviii., p. 1094, 1879. 
 
 2 Compare, regarding the sexual organs of these forms, the statements of van Beneden 
 (" Vers Cestoides," p. 53), and of Sommer and Landois (loc. cit.) Moniez's recent reports 
 (loc. cit. ) on these structures, as specially observed in a new form, Leuckartia, are indeed 
 very divergent, for he disputes the independent existence of nearly all the parts except 
 the yolk-gland, but particularly of the uterus, shell-gland, and ovary. He thinks that, 
 as in Tania, the eggs originate in a cellular mass found in the meshwork of the paren- 
 chyma, provide themselves with yolk-granules, which reach them by ways of their own 
 making, and lastly become surrounded by a shell. My own investigations, which had 
 partly to do with the same objects (Ligula), do not lead me to agree with Moniez's inter- 
 pretation and description, but, on the other hand, I do not deny (p. 312) that the sexual 
 organs and the later formed connective substance both originate from the primarily quite 
 undifferentiated cellular mass of the parenchyma. 
 
 3 I may, however, expressly mention that the presence of this uterine opening has as 
 yet only been observed in few Bothriadse, although its general presence may be presumed 
 from the essential uniformity in the structure of the sexual organs. I am also convinced 
 that a similar opening is to be found in Ligula and Schistocephalus two species, which in 
 spite of the many differences which they exhibit in the organization of their sexual appara- 
 tus, are essentially allied to the Bothriadae. Donnadieu's statements regarding the 
 sexual organs of these animals (Archiv. pJiysiol., 1878), rest upon a complete misconception 
 of their real structure : see the above -cited memoir of Kiessling. Further, if the Tseniadae 
 possessed a uterine opening like the Bothriadae, it would be situated on the at present 
 closed anterior extremity. At least it would be so in the species with a perpendicular 
 uterus, and in those where the uterus assumes a transverse course it would presumably 
 occupy a lateral position. 
 
318 
 
 THE ANATOMY OF CESTODES. 
 
 in the following descriptions. The latter, however, refer mainly to 
 the forms with mesially situated porus, and especially to the genus 
 Dibothrium, or, as it is generally called, Bothriocephodus.' 1 - 
 
 As to the male organs (Fig. 170, A) but little can be said. Anatomi- 
 cally and histologically they resemble the same organs of Tit'iiiadib, and 
 indeed they only differ from them in particulars which are determined 
 by the ventral position of the porus genitalis. Thus the vas deferens 
 starts from the base of the cirrhus-pouch, which is perpendicularly 
 situated upon the ventral surface, and runs down the middle of the 
 joint, under the dorsal surface, as a tolerably wide canal, bending 
 sometimes to the right and sometimes to the left of the middle line. 
 Whether the bulbus musculosus, which in Bothriocephcdus latus lies 
 close behind the cirrhus-pouch, is of wide distribution, cannot be 
 determined without further investigation, but one feels tempted to 
 connect its presence with the above-mentioned position of the cirrhus- 
 pouch, and to interpret it as a pumping apparatus, designed to remove 
 the difficulties attendant upon the transference of the semen, with 
 
 - 
 
 FlQ. 170. Male (A) and female (B) sexual organs of Bothriocephalus 
 latus. ( x 20.) 
 
 which the seminal duct is itself abundantly filled. This filling takes 
 place exclusively at the posterior end, into which the vasa efferentia 
 
 1 Besides Eschricht's classical work on Bothriocephalu* lotus, which we shall often 
 have occasion to quote, it is especially to the already mentioned treatises of Stieda and of 
 Landois and Sommer that we owe our increased knowledge of the structure of the sexual 
 apparatus in Bothriocephalus. The description which I have given in the first edition of 
 this work, although expressing even in details many of our present views, contains a 
 number of errors. These are of course corrected in this edition, and throughout, on the 
 strength of my own observations, which corroborate the results of Stieda and Sommer 
 and Landois. 
 
THE VAGINA AND UTERUS. 319 
 
 of both sides open. The testes are apparently always present in great 
 numbers and pretty equally distributed over the middle layer. 
 
 The vagina and uterus (Fig. 170, B) have, on the whole, the same 
 course as the seminal duct, only differing from it in so far as they lie in 
 another plane. This is especially true of the vagina, which lies upon 
 the ventral surface, very much as the vas deferens lies upon the dorsal 
 surface. These three canals cover one another in their course, and this 
 must be to a large extent the reason why the vagina the narrowest 
 and most insignificant of the three, in spite of its contents of semen 
 has remained only imperfectly known, and was often wholly 
 overlooked till after Stieda's researches. It runs downwards in a 
 pretty straight course, while the uterus, at least in the older joints, 
 forms on each side a number of oval loops. These project a consider- 
 able distance towards the sides, and are all the more conspicuous 
 since they are stuffed full of eggs, and from their dark colour stand 
 out in sharp contrast to the other organs. Only in the narrow 
 posterior part does the uterus exhibit less regular windings, and a 
 more simple structure. Although the hinder portion of the vagina is 
 not unfrequently distended into a sort of caecum, no proper sperm- 
 pouch seems to be present, the whole vagina being, as we have men- 
 tioned, usually filled with semen. 
 
 At the connection of the vagina with the uterus there is also a 
 fertilising canal, which ends in a shell-gland the so-called "coiled 
 gland" of which the real nature was first understood by Stieda, and 
 which I erroneously held to be the ovary. This canal, as in the 
 Taeniadae, receives the efferent canals of the proper reproductive organs. 
 Although there are instances of a more or less marked simplification 
 (Caryopliyllceus) the ovary is, as a rule, of a hand-like or wing- 
 shaped structure, and, except in Ligula, generally exhibits the already 
 familiar symmetrical arrangement. This is the structure which I 
 formerly identified in Bothriocephalas and in the Tcenice as the 
 yolk-gland, which is, however, really represented by the organs de- 
 scribed by Eschricht as ventral and dorsal granules. These yolk- 
 glands are, indeed, the most striking and important characteristics of 
 the Bothriadae, not only on account of their size, but because, unlike 
 the other sexual parts, they belong to cortical layers of the body. In 
 many species they run down the sides of the joint in the form of a 
 pretty large caecal tube, abundantly provided with lateral protube- 
 rances, especially on the outer side. They open ultimately into the 
 vaginal canal by means of an efferent canal, which runs transversely 
 from the middle line, and close beside the shell-gland. They thus 
 exhibit conditions similar to those which we shall afterwards find in 
 the Trematodes conditions, moreover, which may undergo many 
 
320 THE ANATOMY OF CESTODES. 
 
 modifications by the more or less independent development of the 
 caecal tube. This is especially true of Bothriocephalus (sensu stricto) and 
 Ligula, in which these lateral tubes are broken up into a large number 
 of round or oval sacs (Fig. 170), which insinuate themselves between 
 the so-called " subcuticula " and the longitudinal muscles, and when 
 in their usual position, are found not only in the borders, but also over 
 a great part of the lateral portions of both surfaces. Their contents 
 consist mainly of the somewhat large and coarse-grained yolk-cells. 
 These pass into the fertilising canal by means of a branching system 
 (Eschricht's " yellow canals)," and finally in the shell-gland, or in the 
 commencement of the uterus, become enclosed in a firm shell, along 
 with a pale and membraneless ovarian egg. 
 
 At first sight the differences between these yolk-glands of the 
 Bothriocephcdi and the above- described corresponding organ of the 
 Tseniadae appears so striking that one feels inclined to adopt the view 
 of Sommer, who calls the latter an " albuminous gland," and dis- 
 tinguishes it from the " yolk-gland " of the other Cestodes. And this 
 seems all the more likely since the nature of the secretions is different, 
 for while the products of the yolk-gland are granular cells, the albumi- 
 nous gland yields a tough and almost homogeneous fluid. Yet this fact 
 is of little significance, for many differences are also found in the 
 secretion yielded by the yolk -gland, which in the latter instance are 
 dependent on the degree and nature of the breaking up of the cells 
 yielded by the glandular wall In considering these conditions it 
 must not be forgotten that the structures in question do not produce 
 an ordinary yolk, but an envelope for the egg, which, however, like 
 the granular yolk, furnishes nutriment for the embryo, but in its 
 relation to the true egg more nearly resembles the albumen of the 
 bird's egg. For this reason it has often been proposed (especially by 
 Eeichert) to change the name " yolk-gland " for " albumen gland." 
 
 Albumen gland and yolk-gland in these worms are, however, by 
 no means to be regarded as physiological contrasts, or at least they 
 are not so different as might perhaps have been supposed ; and it seems 
 to me also, that in the conditions existing in the Cestodes there is 
 hardly any difference morphologically between the organs in question. 
 
 In support of this statement, I may refer to the structure of the 
 yolk-gland in Caryophyllceus, which, besides the two posteriorly 
 situated lateral tubes, also exhibits a middle portion, corresponding in 
 position and arrangement to the albumen-gland of the Taeniadse. If 
 we suppose the lateral organs to disappear and this supposition is 
 justified to some extent by the smaller yolk requirements of the 
 Tieniadae then the only difference left is that in Caryophyllceus the 
 remaining structure belongs to the cortical layer, but in the Taeniada 1 
 
PRIMITIVE EGGS. 321 
 
 to the middle layer. Yet this is apparently a necessary consequence 
 of the fact that the middle layer of the jointed tape-worms passes 
 continuously, as we have seen, throughout the whole length of the body. 
 
 Consequently I see not the slightest ground for regarding the yolk- 
 gland of the Bothriocephali as quite different from that of the Tgeniadae, 
 nor for describing it by another name, which almost necessarily leads 
 to a different conception of it. 
 
 But without supposing a different nature of the yolk-glands, there 
 are considerable differences between the Tseniadse and the other 
 Cestodes in the structure of the sexual organs. These find their 
 expression in the nature of the eggs, which originate from the opera- 
 tion of the germ-glands. In the Bothriocephali they are at first of 
 a relatively large size, and are composed of a thin shell, generally 
 of oval shape, which encloses the ovarian egg, surrounded by the 
 granular yolk-cells. In contrast to these, the generative products of 
 the Tseniadse, which are first fully formed in the end of the uterus, 
 consist of very small round balls with a clear and almost non-granular 
 yolk, and with only a thin and loose covering, which in many of the 
 larger species is prolonged at one (Tcenia marginata) or at both (T. 
 saginata) ends into a kind of tail. 
 
 FIG. 171. Egg of Eothrio- FIG. 172. Recently formed egg of Tcenia 
 
 cephalus latus, showing yolk- marginata (A, B) and T. elliptica (C). 
 cells and shell. ( x 300.) ( x 600.) 
 
 But if we wish to see the latter in their above depicted primitive 
 form, it is necessary to observe the young, or, as they are generally 
 
 FIG. 173. Embryo containing egg, A, of Tcenia solium (without 
 yolk-skin), , of T. nymphcea. ( x 400. ) 
 
 called, immature joints, in which the uterus is still of its original 
 shape, or in which the lateral branches are just beginning to be formed. 
 In the older and so-called mature joints a peculiar alteration has taken 
 
 x 
 
322 THE ANATOMY OF CESTODES. 
 
 place in these eggs, for they have become large and generally round 
 balls with a more or less firm shell, which contains a clear globule, 
 with six slightly bent hooks (Fig. 173) arranged in pairs anteriorly 
 and laterally. These bodies are the embryos, first accurately observed 
 and described by v. Siebold. 
 
 During the growth of the joint in the Tcenice, the embryonic 
 development also progresses. The older mature joints, whose uterus 
 often appears of a rusty -brown colour from the contained eggs, have 
 gradually become pregnant animals. 
 
 The size of the embryos of Tccnia and of their hooks varies greatly 
 in the different species. This is especially true of the hooks, which 
 often attain a disproportionate development, and 
 become so long that they penetrate the greater 
 part of the embryonic body. And even in the 
 same embryo there may be differences in the 
 degree and manner of their curvature. In 
 general, however, the structure of the hooks has 
 v ^i ; 1 7 ~ Embr y." al a great resemblance to that of the adult Tcenia, 
 
 booklet of Toenia craterifor- 
 
 mis, from a bird. A, a except that as the root has a very straight 
 
 StrS'^telorhtok: course - the general form is more linear. 
 lets. ( x 700, after v. Sie- In some species, such as the Tcenice of birds, 
 **") these hooks often exhibit a distinct motion. 
 
 They approach with their free points a common apex, and in their 
 motion from it diverge downwards, the two side pairs moving almost 
 simultaneously in the lateral plane, and the middle pair somewhat 
 later in a median direction. 
 
 The shell which surrounds these embryos, without, however, lying 
 closely upon them, is sometimes thin and smooth, and is sometimes 
 also furnished with granules or with a number of little perpendicular 
 rods close beside each other, as is especially the case in the larger 
 Cystotcenice (Fig. 173, A). Nor is this always the only covering of 
 
 the embryos. In many species a 
 second and occasionally even a third 
 skin has been found, both of peculiar 
 and striking form. 1 But even in 
 cases where these extra coverings 
 around the shell are wanting, as in 
 
 Fw. 175.-Egg of 2M. nana oc- * e lar S 6r *<**** f ma " alld Caf - 
 
 curring in man, A ; and of T. sotium, nivorous mammals, one sometimes 
 B 9 with shell and yolk skin. ( x 400.) notices> especially if the egg be cau- 
 tiously emptied, an albuminous envelope bordered by membrane. 
 
 1 In this connection see the statements of v. Siebold regarding the egg-shell and form 
 of the eggs in the Tayniae in Burdach's " Physiologic,*' 2 Aufl., Bd. ii., p. 203, 1828-35. 
 
EMBRYOS OF THE TJENIAD.E. 323 
 
 Besides the shelled embryo, this generally encloses a number of 
 shining fatty granules which are often collected in large clusters. In 
 older eggs, this albuminous layer is often completely lost, so that the 
 thick shell is then the only embryonal envelope. 
 
 The difference between these embryo-containing eggs and the 
 original contents of the uterus is so striking, that it is right to in- 
 quire into the processes by which the latter are transformed into the 
 former. This investigation is, however, anything but easy, especially 
 in the large-hooked Tcenice, whose eggs can be isolated only with 
 difficulty. On the strength of my later observations, I am obliged to 
 modify in many ways the statements which I formerly made re- 
 garding the embryonic development of the Tcenice, which were, how- 
 ever, the first published. 1 
 
 I recall, in the first place, that the eggs on which our description 
 is to be based are not simple ovarian eggs, but consist of these, plus an 
 albuminous enveloping substance, which is covered exteriorly by a thin 
 and transparent skin the primitive shell-membrane. The whole struc- 
 ture has the appearance of a more or less spherical ball of about 0'03 
 mm., which at first sight one might easily take for a simple cell with 
 a large vesicular nucleus (0*018 mm.). Only gradually does one per- 
 ceive that the nucleus is surrounded by a narrow, membraiieless coat- 
 ing of protoplasm, which, with its contents, is really the ovarian egg. 
 Besides the latter, the enveloping substance in T. solium and its re- 
 latives generally contains one or two shining fatty bodies of varying 
 size (up to 0*01 mm.), and of a usually homogeneous but sometimes 
 granular nature. Sommer, who describes the bodies as accessory 
 yolk-granules, thinks that they originate directly in the ovary ; and 
 it is true one sometimes finds in it granules similar to, though hardly 
 identical with, those occurring in the protoplasmic envelope. 
 
 As everywhere, the embryonic development of the Tcenice is 
 effected by a division of cells, by a process which seems to associate 
 itself primarily with the persistent and apparently unaltered germinal 
 vesicles. But on account of the small size of the developing mass, and 
 the clear nature of the enveloping protoplasm, this division assumes, 
 especially at first, a very unusual appearance, which easily leads to a 
 wrong conception of it, and which indeed, so long as I was ignorant 
 of the yolk-coating of the ovarian egg, led me to imagine a formation 
 of daughter-cells in the interior of the germinal vesicle. On the whole, 
 
 1 " Blasenbandwiirmer," p. 14, and the first German edition of this work, Bd. i., p. 
 184. See also the descriptions of the younger van Beneden in his " Recherches sur la 
 composition et la signification de 1'ceuf," p. 51 : Brussels, 1870 (Mem. couronn. Acad. 
 Bdg., 1868) ; as also Moniez, Comptes rendus, Nov. 1877, and Bull. sci. dep. du Nord., 
 t.x., p. 227, 1879. 
 
324 THE ANATOMY OF CESTODES. 
 
 the process of division takes place, at least at first, somewhat regularly. 
 The first two divided globules again break up into two pale nucleated 
 balls of equal size, which is of course less than that of the former. 
 When the division has gone further, the segmentation masses collect 
 together, and round themselves off into a spherical body the so- 
 called " mulberry mass " (morula). During these changes the egg has 
 grown to a considerable size, so that the segmented mass alone is 
 larger than the whole mass formerly was. 
 
 One might suppose that this mass of balls changed directly into 
 the later embryo after continuous growth and diminution of its 
 cells, and after the formation of the hooks and shell. But the de- 
 velopment does not take place quite so simply. Van Beneden and 
 Moniez have both observed that in certain species (Tcenia bacillaris, 
 T. expansa) a peripheral layer of cells is first found in the embryonic 
 body, whose elements divide more rapidly, and assume a brighter 
 appearance, than is the case in the other forms. Although at first in 
 close contact with the embryonic body, this cell-layer gradually sepa- 
 rates from it. A cavity is left between the two, at first only in- 
 significant, but rapidly attaining a considerable size, and containing 
 a clear fluid. For a time the cells are distinctly visible around this 
 space, but afterwards they undergo a degenerative process, in conse- 
 quence of which they assume a more or less granular nature, lose 
 their former boundaries, and finally disappear. During these modi- 
 fications the other cell-mass has continued its development. The 
 cells have become smaller, and are so closely packed that they can 
 hardly be recognised as such. In consequence of this the embryonic 
 body has contracted into less bulk. Its boundary has become more 
 distinct, and very soon appears very like a special envelope of homo- 
 geneous nature, which becomes gradually thicker, and raises itself like 
 a mantle from the under layer. Not unfrequently (Tcenia bacillaris, 
 &c.) a second and third envelope appear in addition to this first one. 
 They all originate as excretions from the embryonic body, in the 
 same manner as the so-called egg-shells of Eehinorhynchus.' 1 
 
 Yet it cannot be doubted that the enclosed spherical body is 
 really the embryo. This is evident not only from its developmental 
 history, but perhaps still more clearly from the rapid appearance 
 of the characteristic embryonic hooks. 
 
 It is thus quite inadmissible to compare the firm envelope sur- 
 rounding the embryo in the Tcenice with the egg-shell of the 
 Bothriocephali, which is from the first present in the uterus, and 
 contains not only the embryo but also the yolk. The egg-shell is 
 represented in this case by the outer membranous boundary of the 
 
 1 Fir&t German edition of this work, p. 805. 
 
THE DEVELOPMENT OF THE EMBRYO. 325 
 
 albuminous mass, which takes the place of the yolk, by a structure 
 which in certain Tseniadse also gradually assumes a firm consis- 
 tence. Kegarding the structure of the horn-shaped or thread-like 
 appendages, we have only a single observation of E. van Beneden's 
 to go upon, according to which they are protruded subsequently 
 during the division of the yolk. The statement rests upon the exami- 
 nation of Tcenia bacillaris, which, however, differs in so far that the 
 horns are drawn back during the growth of the embryo, and leave no 
 trace of their presence in the mature eggs. In other cases even the 
 newly formed egg is provided with these appendages. So it is at 
 least in the larger Cystotcenice ; but the appendages vary greatly in 
 individual cases, both as to number and mode of occurrence. 1 I find 
 them most constantly in Tcenia saginata and T. marginata (in the latter 
 oftener one than two), but comparatively seldom in T. serrata. They 
 can also be sometimes demonstrated in the younger eggs of T. elliptica, 
 where again they usually occur singly. I think that they probably 
 originate when the transference into the uterus takes place, and in a 
 purely mechanical manner, by drawing out into threads the secretion 
 supplied by the shell-gland. 
 
 As has long been observed in the case of T. elliptica, certain other 
 alterations take place in the eggs of Tcenice, after the complete maturity 
 of the embryos, for they are collected in groups and surrounded by a 
 firm common envelope (p. 317). The groups always correspond to the 
 contents of a uterine branch, from the walls of which the enveloping mass 
 is distinguished as an originally clear granular substance. The same 
 may be observed in T. litter ata, except that in this case the simply 
 tubular uterus envelops all its egg-masses within a single capsule. 
 
 What we have hitherto said regarding the embryonic development 
 of the Tseniadae is based primarily and specially on observations made 
 by van Beneden and Moniez in certain smaller species. In the species 
 of Cystotcenice which I have specially investigated with regard to these 
 processes, the state of matters is somewhat different, although gene- 
 rally similar, so that it looks as though there might be many modifi- 
 cations in this respect, with which we are as yet only slightly 
 acquainted. 2 
 
 The first phases of the development, before the fourfold division 
 of the eggs, exhibit, it is true, no peculiarities. The yolk-balls are 
 pale cells of about 0'013 mm. with a large vesicular nucleus. They 
 
 1 I owe my first acquaintance with these structures to a communication from my 
 honoured friend E. van Beneden, who discovered them in the eggs of Tcenia saginata. 
 
 2 [E. van Beneden has recently made this process the subject of a thorough investiga- 
 tion, " Recherches sur la developpement embryonaire de quelques Tdnias," Archiv. d. Biol., 
 t. ii., pp. 183-210, 1881. R. L.] 
 
326 
 
 THE ANATOMY OF CESTODES. 
 
 occupy the largest space in the egg (0'03 mm.), and are surrounded 
 by a fine granular substance, in which some coarser shining grains of 
 a fatty nature are generally observed. But afterwards the yolk-cells 
 alter, larger and smaller ones (O007 mm.) can be distinguished, and as 
 the former usually occur in threes, the latter probably originate from one 
 of the four previous balls. And further, it is only those smaller cells 
 which produce the body of the embryo. They multiply without losing 
 perceptibly in size, and gradually collect into a spherical cluster near the 
 large cells, but this mass is larger (0'02 mm.) than the one formerly found 
 within the pale shell-membrane. The vesicular nucleus has a diameter 
 of O08-O1 mm., and a distinctly defined nucleolus. In some cases four 
 or five cells are found instead of three, and it appears as though one of 
 
 FIG. 176. Emlryonic development of Ttrnia scrrata (A ), and T. marginata (B) ; a, eggs 
 before segmentation. ( x 550. ) 
 
 the smaller cells sometimes detached itself from the rest and formed 
 a covering-cell. We can hardly doubt that these larger cells, in spite 
 of their peculiar origin and smaller numbers, are comparable to the 
 already mentioned cell-sheath of other species, for, like it, they do not 
 take the slightest part in the formation of the embryo, but are per- 
 manently present outside it in the surrounding shell. The latter 
 originates in the form of a very delicate and smooth cuticle, as soon 
 as the embryo has attained a size of about 0'02o mm... and has ex- 
 changed the former cellular structure for an almost homogeneous 
 appearance. The rod-like fringe only makes its appearance gradually 
 by the growth of protuberances upon the external surface. As the 
 
COVERING-CELLS AXD CILIA. 
 
 327 
 
 external egg membrane has by this time increased to about 0*06 mm., 
 a considerable space is left between it and the fringe, and this is 
 occupied by the covering-cells, which have also increased in size and 
 proportion to the egg, and are generally so closely packed together, 
 that they are flattened at their points of contact. The original 
 albumen has gradually contracted into the so-called " granular mass." 
 This generally assumes a spherical form, and inserts itself here and 
 there between the covering-cells, and during the growth of the embryo 
 gradually deposits within itself a number of coarse shining granules 
 and fat-like drops. 
 
 After a long stay in the ovary, the covering cells not unfrequently 
 lose their external boundary and are destroyed. Their contents have 
 generally previously assumed a finely granular nature, and in this 
 form can usually be demonstrated for a time lying round the embryo 
 with its vesicular nuclei. This is especially the case in Tcenia serrata, 
 whose covering cells are very considerably smaller than those of T. 
 maryinata and T. saginata. 
 
 The first indications of the embryonic hooks in Tcenia solium and the 
 related forms appear after the formation of the egg-shell, and at about 
 the same time at which the first protuberances are observed upon the 
 shell. They are at first little points, situated on the outer surface of 
 the embryo, which is covered by a soft skin ; and, like the hooks of 
 the tape-worm, they become independent organs, only by the growth 
 and development of the radical process. 
 
 Histologically, the adult embryo exhibits only a slight advance 
 upon its former state. It apparently consists of a uniform, clear sub- 
 stance, in which one can distinguish at 
 most only a number of granular deposits 
 and fatty drops. 
 
 And this is true not only of the 
 Tccnice, but of the majority of the 
 Bothriadae, whose embryos have notably 
 a similar form and armature. Only in 
 the embryos of Jlothriocephalus latus 
 do I find a greater differentiation, for 
 in this case there are not only distinct 
 fibrous bands, which are attached to 
 the roots of the hooks and move the 
 latter, but also four roundish groups of 
 cells embedded in the body, as will after- 
 wards be more particularly described. 
 
 The embryos of the Bothriadre exhibit many other peculiarities 
 in addition to these, both in origin, differentiation, and mode of life. 
 
 'urn 
 
 
 FIG. 177. Ciliated embryo of 
 Bothriocephalus Latus. ( x 500.) 
 
328 
 
 THE AXATOMY OF CESTODES. 
 
 In regard to their mode of origin, the rule is 1 that the embryos 
 are not developed inside the mother's body, as in the Tcenice, but 
 outside it, and often so slowly that weeks and months elapse between 
 the laying of the egg and the time when they attain their definite 
 structure. Being abundantly provided with granular yolk, the eggs 
 of the Bothriocephali by no means require during their development 
 that continuous supply of nourishment necessary for the less favoured 
 Tcenice. 
 
 But not only do the embryos generally develop in free life, but 
 they usually break forth from the egg on the attainment of maturity, 
 and swim about for a time in water by means of a ciliated mantle, 
 until they begin their future parasitism by migration into a living 
 creature. 
 
 The possession of the ciliated apparatus is indeed the most impor- 
 portant and striking peculiarity of these embryos. We have observed 
 it not only in the different species of Boihriocephalus, but in Trice- 
 nophorus, Liyula, Schistocephalus, &c., and may thus presume that it 
 is widely distributed in the allied species. The cilia are generally 
 of considerable length, and are based upon a firm cuticular mem- 
 brane, which is at some distance from the embryonic body. In 
 young embryos (Fig. 177) the space is occupied by a layer of clear 
 
 and relatively large cells of an 
 almost bubble-like appearance, 
 which have between them nume- 
 rous sharply defined granules 
 with strong refractive power. 
 Older embryos exhibit only the 
 latter, the place of the cells being 
 occupied by a clear fluid. 
 
 This mantle occurs, however, 
 not only in the roving embryos, 
 but also in those which, like the 
 Tcenice, remain in the egg, and 
 are thus of course only adapted 
 for passive migration. We have 
 therefore good reason to con- 
 
 FIG. 178. Embryonic development of 
 Bothriocephalus salmonis (after Kolliker). 
 (x 300.) 
 
 Bothriadse. 2 
 
 sider its presence as an almost 
 universal characteristic of the 
 Yet it will hardly surprise us to learn, from the de- 
 
 1 See on this subject the comparisons of v. Willemoes-Suhm, Zcitschr. f, wiss. Zool., 
 Bd. xxiii., p. 345, 1873. 
 
 a According to v. Siebold, there are, however, some exceptions in regard to this. See 
 Willemoes-Suhm, Zeitschr. f. wiss. Zool, Bd. xxiii., p. 344, 1873. 
 
EMBRYOS OF THE BOTHRIAD.E. 329 
 
 velopmental history, that this mantle-like structure is nothing else 
 than the further development of that same peripheral cell layer, with 
 which we are already familar in the embryos of the Taeniadse. 
 
 What we know regarding the embryonic development of the 
 Bothriocephali is due mainly to the investigations of Kolliker 1 and 
 Mecznikoff, 2 which both refer to Bothriocephalus proboscideus (B. 
 salmonis), whose embryos are produced in the mother, and whose 
 other conditions, in spite of the divergent nature of the ovary, agree 
 in all important respects with the embryonic history of the Tasniadse. 
 
 In the Bothriadae also it is only the germ-cell (germinal vesicle of 
 Kolliker) which forms the embryo ; the granular yolk-mass has no 
 more direct share in its formation than had the more albuminoid 
 matter of the Tcenice. A spherical mass of cells results from a com- 
 plete and regular segmentation. This becomes differentiated into a 
 central nucleus and a peripheral layer, as we have seen in some Tcenice. 
 This peripheral layer becomes the above-mentioned embryonic enve- 
 lope, which is destitute of cilia in Bothriocephalus proboscideus, but is 
 nevertheless homologous with the similarly originated ciliated covering 
 of B. latus. During the transformation of the nucleus into the body 
 of the embryo this layer loses (according to Mecznikoff) its early 
 cellular structure, and becomes a simple cuticular membrane enclosing 
 the embryo. 
 
 As to the comparative embryology of this peripheral layer, we can 
 only liken it to the ectoderm. This ectoderm, however, is never 
 retained in later life. Even the species with a ciliated coating are 
 stripped of it as soon as they migrate into their host. Thus we 
 conclude that the tape-worms have no ectoderm a conclusion to 
 which we were formerly led by histological considerations (p. 289), 
 which forced us to deny the existence of any true subcuticula. 
 
 The statement of the older van Beneden, that some Bothriada3 
 liberate their eggs in the Scolex form, is utterly without foundation, as is 
 also the assertion that the embryos are in some cases without booklets. 
 We have indeed come to know of a form in the genus Amphiline in 
 which ten hooks are present, 3 instead of the usual six, or the four which 
 occasionally occur in Bothriadae. It is, however, doubtful whether 
 these forms ought to be referred to the Cestodes (p. 268). Yet it is 
 interesting to note that even among the genuine representatives of the 
 Cestodes embryos are sometimes found which have more than the 
 normal six hooks. Thus Heller mentions instances of embryos of Tccnia, 
 saginata with twelve, sixteen, and even thirty-two hooklets, some of 
 
 1 Mullcr's Archivf. Anat. u. PhysioL, p. 91, 1843. 
 
 2 Bull. Acad. imptr. St. Pttersbourg, t. xiii., p. 290, 1869. 
 
 3 Salensky, Zeitschr. f. wiss. Zool., Bd. xxiv., p. 291, 1871 
 
330 THE DEVELOPMENT OF CESTODES. 
 
 which were perfectly developed, but others appeared only as short 
 blunt protuberances. 1 Moniez also speaks of tape-worm embryos with 
 twelve hooks. I have myself seen such cases in T. saginata and 
 T. elliptica, and Professor Ramsay- Wright has showed me, in my 
 laboratory here, embryos with ten and even twenty-four hooks. The 
 embryos are considerably larger than usual, some twice as large, and 
 they bear their hooks in groups of about six on only one-half of the 
 body. 
 
 The statement of 0. Schmidt, lately reasserted by Kiichenmeister, 
 that the six-hooked embryos of the Tcenia dispar occurring in the 
 common frog are the result of an asexual reproduction 2 is quite 
 erroneous ; it is by no means difficult to demonstrate the existence of 
 their generative organs. 
 
 The Development of Cestodes. 
 
 G. Wagener, " Die Entwickelung derCestoden," Nova ActaAcad. Goes. Lcop.-CaroL t 
 Bd. xxiv., Suppl. 1854 ; also Breslau, 1854. 
 
 R. Leuckart, " Die Blasenbandwiirmer und ihre Entwickelung," Giessen, 1856. 
 Moniez, "Sur lea Cysticerques," BuU. tci. dep. Xord, t. x., p. 284, 1879. 
 
 The above account of the formation of Cestode embryos has shown 
 us that the young brood has not the least resemblance to the adult 
 forms. The young embryos (Fig. 179) are microscopic balls, with 
 usually six apical hooks, and differ widely from the tape-worm, both 
 in shape and size. Between these two extremes we find a long series 
 of wonderful metamorphoses. 
 
 Thirty years ago the further development of these embryos 
 was wholly unknown. Dujardin supposed that they were liberated 
 in the intestine of their host, that they passed 
 by simple metamorphosis into the so-called " head," 
 and afterwards, by forming joints, became the 
 familiar tape- worm. 3 Even v. Siebold seemed at 
 Fio 179. Embryo of first 4 inclined to suppose that the six-hooked em- 
 Tania. (xioo.) bryos passed directly into the subsequent tape- 
 worm, and only opposed Dujardin by urging that this change could 
 hardly take place in the original habitat of the mother-animal, " since 
 the young brood was so seldom found near the Cestodes." The change 
 
 1 Ziemssen's " Handb. d. sp. Path. u. Ther.," Art. "Darmschmarotzer," Bd. vii., 2, p. 
 600 ; Eng. TransL, " Cyclop. Pract. Med." vol. vii., London, 1877. 
 8 Zeitschr.f. d. gesammt. Naturwiss., Bd. v., 1855. 
 
 3 Ann. Sci. nat., t. xx., p. 841, 1843 ; or, " Hist. nat. des Helminthes," pp. 545, 633, 
 1845. 
 
 4 Art. " Parasiten" in Wagner's " Handworterbuch der Physiologic," Bd. ii , p. 673, 
 Brunswick, 1843. 
 
OLDER VIEWS ON THE SUBJECT. 
 
 331 
 
 must therefore presuppose an emigration from the original host, and 
 a transference to another victim. Afterwards v. Siebold declared 
 that the embryo took the form of a tape-worm head " outside the in- 
 testine of the vertebrate host," and subsequently gained a new home. 
 He gives no hint, however, as to the manner of the metamorphosis. 
 In fact there were no direct results of observation to go upon ; all the 
 statements were more or less plausible inductions. 
 
 Von Siebold's opinion received its first actual corroboration by an 
 observation of Stein. 1 He found in the body-cavity of Tenebrio 
 molitor and its larvae numerous 
 cysts, which exhibited a tape- worm - 
 like head enclosed in a bladder. 
 This had obviously resulted from 
 the metamorphosis of the six- 
 hooked embryo, as the six hooks 
 still adhering plainly indicated. 
 In some cysts there was only a 
 simple roundish body, without a 
 tape-worm head ; in others the for- 
 mation of the latter could be seen 
 going on within this body. As to 
 the origin of the tape-worms, 2 it 
 could not be doubted that the ,-, 1Qn ,-, . .. 
 
 IG. 180. Encapsuled tape- worm embryo 
 TenebriO had devoured tape- (A\ and the resulting cystic worm, from 
 
 worm eggs, whose enclosed em- Tenebrio 1nolitor ( x 10 )- ( After Stein -) 
 bryos had been liberated by the digestion of the egg-shell, and had 
 wandered through the intestinal wall into the body-cavity, where 
 they had lost their hooks, become encapsuled, and produced the tape- 
 worm head. 
 
 Before the publication of these researches our knowledge of the 
 development of the tape- worms had been further increased by 
 Kiichenmeister's proof that the bladder-worm of the rabbit (Cysti- 
 cercus pisiformis) became a tape- worm (Tcenia) in the intestine of 
 the dog. 3 
 
 The interest excited by this report was all the more intense since 
 it was the first instance of a " feeding " experiment. This result 
 had been attained by experiment, and it was speedily corroborated 
 
 1 " Ueber den Generation swechsel der Cestoden ;" Zeitschr. f. wiss. Zool., Bd. ii., p. 
 210, 1850. " Beitrage zur Entwickelungsgesch. d. Eingeweidewiirmer, " ibid., Bd. iv. p. 
 205, 1852. 
 
 2 Probably these were the larvae of a Tcenia occurring in its adult form in the mouse 
 (Tcenia inurina). 
 
 3 Gtinsburg's Zeitschr. f. klin. Vortrage, p. 240, 1851. 
 
332 THE DEVELOPMENT OF CESTODFS. 
 
 and extended both by Kiichenmeister 1 and by v. Siebold 2 and his 
 school. 
 
 After these experiments it could no longer be doubted that the 
 bladder-worms stood in definite genetic relations with tape-worms, 
 and particularly with Tcenice. 
 
 In order to appreciate the full import of this discovery, we must 
 remember that since the time of Zeder and Eudolphi the cystic worms 
 were commonly regarded as representatives of a special group of Hel- 
 minths the Cystici. It was of course known that these bladder- 
 worms exactly resembled Tcenice in the formation of their head, but 
 the presence of a water-bladder, instead of a ribbon-like jointed body, 
 was considered distinctive. It was this same characteristic which had 
 concealed the true, or even the animal, nature of these organisms till 
 towards the end of the seventeenth century, when the researches of 
 Hartmann, Tyson, and Malpighi showed that it was no longer possible 
 to regard them as simple hydatids. 3 Their occurrence in parenchy- 
 matous organs seemed also a sufficient reason for separating them from 
 the tape- worms, to which they had been already referred by Pallas 
 and Gb'ze. 4 As to the absence of sexual organs in these cystic worms, 
 that was hardly a difficulty. The calcareous bodies (p. 281) were in 
 fact often regarded as eggs, and when the true state of the case was 
 noticed, it was only another proof of the generatio cequivoca. 
 
 The result of Kiichenmeister's experiments, though new, and sur- 
 prising to the majority of physicians and zoologists, was yet not 
 altogether unforeseen. Dujardin and v. Siebold had already advanced 
 the supposition that the bladder-worms were not independent animals, 
 but only developmental stages of Tcenice. 6 Both supposed that the 
 cystic worms were developed out of tape- worm germs which had reached 
 the body-parenchyma, instead of only the alimentary canal of their 
 host, and had, in consequence of the unwonted environment, become 
 abnormally modified. Von Siebold especially supported this theory 
 of the degeneration of tape-worms into bladder-worms. 6 The tape- 
 
 1 " Ueber die Umwandlung d. Finnen in Taenien," Prager Vierteljahrsschr., 1852. 
 
 a " Ueber die Verwandlung des Cysticercus pisiformis in Taenia serrata," Zeitschr. f. 
 wiss. Zool., Bd. iv., p. 400, 1852 ; and as to the metamorphosis of Echinococcus -brood into 
 Tcenice, ibid., p. 409. (Lewald, " De cysticercorum in taenias metamorphosi," Dissert, 
 inaug. Wratislav, 1852.) 
 
 3 See, in greater detail, Leuckart, loc. cit. , pp. 1 -27, &c. 
 
 * In his group of tape-worms Goze distinguished the Tcenice intcstinales inhabiting 
 the intestine, and the Tcenice viscerales occurring elsewhere. Others united the cystic 
 worms to the other Tcenice under the title Tcenice vesiculares. 
 
 6 In the second edition of his work (" Parasiten," p. 60, note), Kuchenmeister 
 underrates v. Siebold's share in the solution of the problem in a way which is, to every 
 unprejudiced critic, utterly unfair, and he accompanies it with the unparalleled assertion 
 (p. 163, note) that "no one has so grievously offended in the study of the Cestodes" as the 
 " Professor of Zoology" strictly Professor of Anatomy and Physiology Rudolphi. 
 
 6 See especially Zeitschr. f. wiss. Zool., Bd. ii., p. 200, 1850. 
 
CONNECTION BETWEEN TAPE AND BLADDER WORMS. 333 
 
 worm heads which the latter possess form an appendage, but on this 
 strange soil this gets changed by " dropsy " into a bladder. 
 
 Von Siebold gave his theories special point and weight by taking 
 a special case of resemblance, instead of merely dilating on the general 
 similarity ; he emphasised the likeness between the head of the cystic 
 worm infesting the mouse (Cysticercus fasciolaris) and the tape-worm 
 of the cat (Tcenia crassicollis}, a comparison which had been previously 
 expressly made by Pallas and Goze. 1 " Some individuals of the brood 
 of Tcenia crassicollis" he says, " go astray in the rodents, and degene- 
 rate into Cysticercus fasciolaris; but when their hosts are eaten by 
 cats, and the worms are thus transplanted to their fit soil, they cast 
 off their degenerate joints, and, returning to the normal form of Tcenia 
 crassicollis, become sexually mature." 
 
 To this theory v. Siebold clung all the more firmly when he found 
 Klichenmeister's results confirmed by his own experiments. 
 
 In the changes undergone by the bladder- worm after their trans- 
 mission into the intestinal canal, 2 he recognised no normal meta- 
 morphosis, but only the remedying of a previous abnormality. When 
 the bladder- worms had altered their form in their new environment 
 he called them " healthy," and thought that there were only certain 
 forms which could pass through such fates to the tape-worm stage. 
 
 I must confess that I shared v. Siebold's theory for a while. 3 I 
 was unfortunately as little aware as v. Siebold of the beautiful ob- 
 servations which Goze had made on the development of the cystic 
 worms, and especially of that form found in the mouse, which was the 
 more unfortunate since these observations were in reality decisive on 
 the point in question, and gave a direct proof, not of the pre-existence 
 of the head, but of the bladder. " The first thing," said Goze, 4 "to 
 
 1 See Pallas, " Miscell. Zoolog.," p. 170, and Neuc nordische Beitrage, Bd. i., p. 82 ; 
 Goze, loc. cit., pp. 222, 304. The latter speaks as follows: "In size, shape, and 
 structure, the head of the Tcenia serrata fdina ( = T. crassicollis) is wholly identical with 
 the head of the jointed bladder tape-worm from the liver of the mouse, for the latter also 
 has no neck, but has its head directly contiguous with the first joint. But why these two 
 forms are so similar in the structure of their head, and yet so different in other respects 
 who can tell ? " 
 
 2 Zeitschr.f. wiss. Zod., Bd. iv., p. 407, 1852. 
 
 8 " Beobachtungen und Reflexionen uber die Naturgeschichte der Blasenwurmer, " 
 Archivf. Naturgesch., Jahrg. xiv., Bd. i., p. 7, 1848. According to Kuchenmeister (" Para- 
 siten," 2ded., p. 19), I held, even in 1857, that the grouping of the Cystici along with the 
 tape- worms was entirely un warrantable ; nay, " I then had no idea of the systematic 
 relation of the two forms." These assertions, dogmatic as they sound, only show that 
 Kiichenmeister's literary-historical studies are not less superficial than his anatomical and 
 embryological ones. I am in no way responsible for van der Hoeven's "Handbook of 
 Zoology," nor for the translation of the first volume which appeared in 1851, on which 
 Kuchenmeister has relied for the truth of his statements. 
 
 4 " Versuch einer Naturgeschichte der Eingeweidewiirmer," p. 245, 17S2. 
 
334 THE DEVELOPMENT OF CESTODES. 
 
 appear in the development of the cystic worm from the egg is the 
 caudal bladder." The so-called head rises subsequently, " invaginated" 
 in the interior of the bladder, " like a candle within a lantern." We 
 have to thank G. Wagener * for having called attention to these for- 
 gotten researches, and for having confirmed them by observations of 
 his own. 
 
 Even v. Siebold found himself compelled to abandon the idea that 
 the formation of the bladder was a secondary and abnormal process. 
 This was due much less to Kuchenmeister's polemic 2 against the 
 theory of degenerate and strayed worms than to the above observa- 
 tions on the encysted tape -worms of Tenebrio, whose resemblance 
 to the bladder -worms was so great that even Stein declared the 
 Cysticerci to be nothing else than the second post-embryonic stage 
 of certain Tcenice. Correct as this statement was, Stein could not 
 perfectly escape the influence of Siebold's theory. He did not venture 
 fully to identify the bladder- worms with the encysted tape- worms, 
 but noted the following distinction between them " that the former 
 seemed to be pathologically degenerated by the accumulation of a 
 dropsical fluid in the hinder part of the body, and would possibly 
 never be able to become mature tape-worms." 
 
 This is, indeed, the opinion which is maintained by v. Siebold in 
 his later work on tape-worms and bladder- worms, 3 and which, sup- 
 ported by the authority of a famous name, has still been held by 
 many even within the last few years. 
 
 The morphological identity between the Cysticerci and the " second 
 developmental stage" of the Cestodes had been asserted by van 
 Beneden* even before Stein. It was, it is true, in connection, not 
 with Tcenice, but with marine tape- worms the Tetrarhynclii that 
 the former had studied this second stage, but that does not in any 
 way affect the importance of his statement. On the contrary, he 
 thereby further proved that the cystic stage was in nowise confined 
 to the Tcenice, but had a wide, perhaps general, distribution among 
 the Cestodes. 
 
 But not only did van Beneden prove the existence of a cysticercoid 
 stage in the Tetrarhynchi ; he also called attention to this fact, that 
 the cysticercoid Tetrarhynchus (Anthocephalus) was found especially 
 in the bony fish, and that they afterwards passed over to the rays 
 and sharks, in which the adult Tetrarhynchus (Rkynchobothrius) was 
 
 1 "Enthelininthica.," Dissert, inaug. Berol., p. 30, 1843. 
 
 2 "Die Cestoden im Allgemeinen, " Prager Vierteljahrsschr., loc. cit., p. 9 et seq., 1853. 
 s " Ueber die Band- und Blasenwiirmer nebst einer Eiuleiturig liber die Entstehung 
 
 der Eingeweidewurmer,*' p. 60, 1854. 
 * -'Lea vers Cestoides," p. 83, 1850. 
 
KUCHENMEISTER'S EXPERIMENT. 335 
 
 found. This transference occurred, of course, when the first hosts 
 were eaten by the second. In a great many instances he was even 
 able to follow the metamorphoses step by step, and thus really to 
 prove that in these marine Cestodes the already supposed division of 
 the developmental history into two epochs or stages, spent in different 
 hosts, was an actual fact. 
 
 The observations of van Beneden would have made more im- 
 pression if the illustrious zoologist had been able to trace the 
 development back to the six-hooked embryo. The existence of this 
 embryo was unfortunately but little attended to, and the formation 
 of the cysticercoid forms was connected simply with a stage in which 
 the young worm (Scolex, Eud.) had essentially the organization of the 
 subsequently formed head. 
 
 And further, van Beneden agreed with v. Siebold in thinking that 
 the cysticercoid stage of the Cestodes was not absolutely necessary 
 but rather accidental, and that it only occurred when the germ was 
 not directly transferred to the alimentary canal. 1 In this way the 
 migrations described by van Beneden lost a large part of their 
 significance. They were characterised more as accidental than as 
 normal processes. 2 
 
 Our knowledge of the development of the Cestodes was thus still 
 far from satisfactory. It was Kuchenmeister again who led us in the 
 right direction by a fortunate experiment. 
 
 In August 1853 Kuchenmeister 3 fed a wether with the ripe pro- 
 glottides of a tape- worm, which had been reared in the intestine 
 of a dog from the familiar bladder-worm of the sheep (Cwnurus). 
 Eighteen days after he found in the brain of the now diseased wether 
 a number of small round bladders, which he identified with young 
 Ocenuri, and which were in fact perfectly identical with the bladders 
 which Haubner had described as their first stage. 
 
 Thus it was proved that the six-hooked Cestode embryo, if trans- 
 ferred to the alimentary canal of an animal, wanders from the latter, 
 and settling in other organs, often far removed, becomes by metamor- 
 phosis a bladder-worm. 
 
 1 " Je crois que le phenomene de 1'involvation (i.e., the formation of a cysticercoid 
 Tetrarhynchus) ne se montre que chez les Scolex qui arrivent dans les replis pe'ritone'aux, 
 coinme aussi les Scolex de Teuia ne deviennent Cysticerques que dans des conditions 
 analogues." Loc. cit., p. 82. 
 
 2 Afterwards, in his great work on the intestinal worms, which appeared in 1858, and 
 therefore several years after the researches of Kuchenmeister, v. Siebold, Wagener, and 
 myself, he abandoned his earlier theory, and correctly explained the life-history and de- 
 velopment of the Cestodes. It is, therefore, hardly consistent with historical fact for van 
 Beneden to claim, as he does in a recent work (" Die Schmarotzer des Thierreiches," p. 
 119, 1876), that he was the first to disclose the true meaning of Cestode development. 
 
 8 Giinsburg's Zeitschr. /. Tdin. Vortrdge, p. 448, 1853. 
 
336 THE DEVELOPMENT OF CESTODES. 
 
 This experiment of Kiichenmeister did not long remain alone. 
 Even before it was published I had made a similar experiment with 
 the eggs of the tape- worm of the cat (T. crassicollis). I fed a number 
 of mice with these eggs, and was able very soon after Kiichenmeister 
 to report 1 that five of the six mice experimented on were found to 
 have their livers infested with bladder- worms (Cysticercus fasciolaris), 
 while those not fed remained perfectly healthy. 
 
 The important results of the experimental method became still 
 more evident when Haubner and Kiichenmeister, working with 
 abundant material at the expense of the Government of Saxony, 
 proved that they could, in the above described way, produce the 
 familiar forms of bladder-worm at will and in the greatest abun- 
 dance. 2 And it was always only the "dropsically degenerated" 
 bladder- worms which grew into mature tape-worms when transferred 
 by feeding to other suitable hosts. 
 
 Xor were such experiments confined to Saxony under Klichen- 
 meister's eyes, but had equally successful results in Berlin, Louvain, 
 Copenhagen, Giessen, Vienna, and afterwards also in Toulouse, Alfort, 
 London, &c. Specially convincing was the result of a "feeding" 
 experiment made simultaneously with some of Kuchenmeister's 
 material (Tccnia ccenurus) by van Beneden in Louvain, Eschricht in 
 Copenhagen, and by me in Giessen, in all which the animals under 
 experiment (lambs) became pathologically affected with exactly 
 identical phenomena. 3 
 
 After these abundant and harmonious results, the migrations and 
 metamorphosis of the six-hooked tape-worm embryos could no longer 
 be regarded as abnormal. 
 
 But the task of scientific investigation was not yet ended. It was 
 still necessary to follow the gradual development of the bladder- 
 worm from the embryo, and to demonstrate the ways and means by 
 which the latter reached the host, and the organ in which it was to 
 undergo its further development. And in this connection I think I 
 may claim some share in advancing our knowledge of the Cestode 
 development, and that through numerous methodical feeding experi- 
 ments. 4 
 
 But before I shortly summarise these results, I must glance at the 
 
 1 Getting, gel. Anzeigen, No. 66, 1854 (report on Kuchenmeister's work on Cestodes) ; 
 GurUs Mag. f. Thierarzneikunde, p. 263, 1854. 
 
 a Gurtts Mag., p. 243, 1854 (Cosnurus], p. 367 (Cysticercus pisiformis, C. tcnuicoUis, 
 Ccenurus), p. 100, 1855 (C. cdluLosce, Caenurus). 
 
 3 Gurlt's Mag., p. 504, 1854. 
 
 * "Amtlicher Bericht der Gottinger Naturf.-Versammlung," p. 89, 1854; Ann. 
 Sd. Nat., t. iii., p. 351, 1855 ; "Die Blasenwiirmer und ihre Eutwickelung," p. 74 et seq. 
 1856. 
 
DURATION OF THE CAPACITY FOR DEVELOPMENT. 337 
 
 objection formerly often urged that an essentially new factor in 
 the life-history of the animal was introduced by such experiments. In 
 reality, the experiment is only a methodical repetition of natural pro- 
 cesses. Just as the animals experimented on were in this case com- 
 pelled to swallow a tape-worm joint, so they do unconsciously and by 
 chance in the unconstrained course of nature. The proglottides gain 
 the exterior occasionally by spontaneous effort, but usually along with 
 the faeces ; they are capable of some motion ; they represent, as we 
 have seen, not joints, but independent animals. In warm, damp en- 
 vironment they can retain their motion and life even for days. They 
 leave the filthy surroundings in which they first find themselves, and 
 seek another abode. Like snails they creep along the ground, climb- 
 ing up a stalk of grass or shrub, and waiting there till eaten by some 
 animal or other. In the dung-eating swine, &c., the transmission is 
 effected directly from the dung. If the new host afford the requisite 
 environment, then the embryos lose their egg-shells and begin their 
 internal wanderings and metamorphoses. 
 
 The characteristic and advantage of experiment, as opposed to obser- 
 vation of the natural process, lies in the choice of the host and the 
 control of the amount introduced. I will not indeed assert that 
 the young brood of the tape- worms always reach their host surrounded 
 by their living parent covering. Apart from those cases (Bothriadse) 
 in which the eggs are liberated and reach the exterior by themselves, 
 the same result might easily follow from the death or rupture of the 
 expelled proglottis. In favourable conditions these isolated eggs 
 remain for long capable of further development. I have been able to 
 infect rabbits with eggs of Tcenia serrata, which had (in September) 
 been kept twelve days in water, and similarly, Eoll in Vienna, has 
 had successful results with proglottides which has lain ten days in 
 the open air, and which had even begun to get covered with mould. 
 It is not yet possible to tell how long this potency can be retained ; 
 the period will doubtless vary with the environment. While Gerlach 1 
 was able to infect a pig with decaying proglottides of Tcenia solium 
 five weeks old, in an experiment I made, the eggs of Tcenia ccenurus 
 had lost potency after lying in water for eight weeks. 2 This follows 
 more rapidly when the eggs are kept dry. Haubner reports having 
 ineffectually fed a sheep with tape-worm eggs which had been kept dry 
 for fourteen and for twenty -four days, and I have had similar experi- 
 ence in which eggs exposed to an August sun had lost their power 
 of germinating after four-and-twenty hours. 
 
 1 Zweiter Jahresber. d. Jcgl. Thierarzneischule, p. 66, Hanover, 1869. 
 
 2 Davaine, on the other hand, asserts that he has kept eggs of Tcenia solium and Tcenia 
 serrata in water for years, living and unaltered. (Mem. Soc. biolog., t. iii, p. 272, 1862.) 
 
 Y 
 
338 THE DEVELOPMENT OF CESTODES. 
 
 These isolated eggs, then, may also find their way into the intestine 
 of their host along with food and drink, and develop farther if they 
 have retained their germinal potency, and if the environment be 
 favourable. 
 
 A spontaneous liberation of the embryo does not occur in the 
 Tcenice. There are, however, Cestodes, as we have mentioned, in 
 which this does occur, but these all belong to the species with uterine 
 opening, and with large yolk-containing eggs that is, to the group 
 of the Bothriadse. 1 In such cases the embryos (Fig. 177) possess a 
 ciliated coat, by means of which they swim about after liberation. 
 The process of getting free is easy enough since the eggs of these 
 species are provided at one pole with a little lid (Fig. 171), which is 
 lifted up in obedience to pressure from within. In the Tseniadae 
 there is no such apparatus ; the eggs have a completely closed shell 
 (Figs. 173 and 175), and the embryos only become free after the eggs 
 have been transported into the stomach of an animal where the shell 
 is dissolved or softened by the digestive juices. 
 
 According to my researches on rabbits fed with eggs and proglot- 
 tides of the Tcenia serrata of the dog, this liberation takes place in 
 about four or five hours after the transference, and therefore at a 
 time when the fleshy mass of the proglottides has yielded to the 
 digestive juices. When the resistance is less, the time required will 
 also be less. In the species named, which is probably representative 
 of the other cystic tape- worms, it is not strictly a solution of the shell 
 that liberates the embryo, but rather a rupture, which results from its 
 increasing brittleness and the internal movements of the hooks. 
 
 After becoming free, the embryos seem to pass some little time in 
 the stomach. Some at once begin by means of their hooks to bore 
 through the gastric walls to some other organ ; others pass directly to 
 the intestine, whence they also bore their way, usually at some distance 
 from the pylorus. It has not indeed been as yet possible to capture 
 the six-hooked embryo in its passage through the intestinal wall, but 
 this is hardly to be expected in the higher and larger animals ; nor 
 have other animals been as yet investigated in reference to this point. 
 Yet there can be no doubt as to the fact that the embryos do really 
 perforate the wall of the intestine; 2 they are in their subsequent 
 
 1 The discovery of these ciliated embryos is due to Schubart, who was first able to 
 develop the eggs of Bothrloccphalus latus. The early death of this promising young in- 
 vestigator hindered the publication of his observations, so that they were first made 
 known at the Bonn Naturalists' Meeting in 1857, through his friend Verloren, who 
 exhibited Schubart's illustrations. The report of Platner, according to which a ciliated 
 coating is also to be observed in the early stage of the embryo of Tcenia solium, is based 
 on error (Muller's Archiv f. Anat. u. Physiol., p. 278, 1859). 
 
 [Raum (Beitrage zur EntwickelungPgesch. d. Cysticercen," p. 28 : Dorpat, 1883) 
 
WANDERINGS OF THE EMBRYOS. 339 
 
 stages found, according to circumstances, in the most diverse organs, 
 now in the liver or in the lungs, now in the muscles or in the connec- 
 tive tissue, and even in the "brain and eye. It is, however, generally 
 the liver which is temporarily or permanently inhabited by cystic 
 worms. 
 
 Ktichenmeister has tried to explain this special preference for the 
 liver 1 by supposing that the six-hooked brood, after becoming free, 
 seek out the bile-duct, and thus pass directly into the liver, but there 
 is no warrant for this supposition. I have examined perhaps a dozen 
 rabbits in the course of the first day or two after infection, and I never 
 found the embryos in the bile-ducts, though their presence there could 
 have been detected without much difficulty. On the other hand, I 
 have several times succeeded in finding unchanged embryos in the 
 portal vein, and have thus proved that at least some of the wandering 
 embryos get into the venous system, and are carried through their host 
 by the blood-stream. 2 With this agrees Leiseriiig's 3 statement that in 
 the case of a lamb which was fed with Tcenia marginata, and died five 
 days after with symptoms of icterus, he found " hundreds " of small 
 " point-like " worms in the much enlarged network of the portal vein. 
 These could be nothing but the further development of the young 
 brood, although the embryos of T. serrata would, as we shall see, by 
 that time have reached and become encapsuled in the liver. It is 
 therefore natural to connect the frequent occurrence of cystic worms 
 in the liver with their wanderings into the blood-vessels, since the 
 capillary network in the liver is the first at which the embryos would 
 arrive, and since the size of the latter (on an average about 0*022- 
 0'028 mm.) hardly admits of a free passage. 
 
 It is, of course, still a moot-point whether this is the only way 
 which the embryos can successfully pursue. This much at least is 
 certain, that there are tape-worms which do not spend their youth in 
 the liver with anything like the same constancy as Tcenia serrata and 
 T. marginata, but are indeed found far more frequently in other 
 organs, such as the muscles or brain. Judging from the mode of dis- 
 
 has actually found the embryos of Tcenia, crassicollis in the intestinal wall of the mouse. 
 It was especially the middle portion of the small intestine where the embryos were seen in 
 the free condition, and sometimes in such numbers that ten could be counted in one field 
 of the microscope. R. L.]. 
 
 1 So at least in the first edition of his work on parasites. Afterwards, in the second 
 edition (p. 52), he supposes that the parasites are carried throughout the body by the 
 blood and lymphatic vessels, especially by the latter. 
 
 2 [In agreement with this, Raum (loc. cit., p. 30) has found six-hooked embryos of 
 Tcenia crassicollis in blood from the portal vein of mice, into which they had been intro- 
 duced nine, twenty-seven, and fifty-two hours previously ; as also in the capillaries of the 
 liver, where their further development could also be studied. The bile-duct was free from 
 embryos. R. L.] 
 
 Bericht iiber das Veterinarwesen Sachsens, p. 22, 1857-58. 
 
340 THE DEVELOPMENT OF CESTODES. 
 
 tribution which I have established in the case of Trichina, one is in- 
 clined to suppose that in the above cases the wandering is through 
 the connective tissue substance, and that the embryos bore through 
 the intestinal wall into the body-cavity, in which they wander where 
 they will. I am inclined to support this theory, particularly in the 
 case of the common tape-worm of man, which presents in its occur- 
 rence and the distribution of its cystic forms close resemblances to 
 Trichina. 1 
 
 When the six-hooked embryos have once reached their future 
 resting-place their further development begins. Originally percep- 
 tible only by help of the microscope, they increase so rapidly that 
 they are often in a few days visible to the naked eye. Further, 
 by their pressure on the infected organs, the growing worms cause a 
 proliferation of cells which, completely surrounding the worms, make 
 them look larger than they really are. These cells become in course 
 of time the coating of the cystic bladder, provided no change of posi- 
 tion occurs. 
 
 In many cases this proliferation of cells is so marked that it has 
 been reckoned as the result of a decidedly inflammatory process. 
 Thus the Ccenuri, which wander into the lamb's brain (Fig. 181), sur- 
 round themselves with a thick, exuded sheath, which becomes drawn 
 out into long bands, in consequence of continued wandering (p. 135). 
 Similarly, in the rabbits infected 2 with T&nia serrata, the liver was, on 
 the fourth or fifth day after infection, seen to be studded with white 
 
 FIG. 181. Brain of a lamb with passages of Ccenurus (natural size). 
 
 points or knots, which were most deceptively like miliary tubercles, 
 but in two or three days after had grown to 0*5 mm., and were, 
 like the Coccidium-nodules (p. 207), surrounded by an envelope of 
 connective tissue. 3 The young bladder- worm lying inside is much 
 
 1 Thus, according to Fiirstenberg, the embryos of Tcenia coenurus reach the brain 
 through the foramina, via the connective tissue. (Ann. d. Landwirthschaft in den Tcgl. 
 prcuss. Staaten, Jahrg. xxiii., pp. 43 and 166, 1865.) 
 
 2 See " Blasenbandwurmer," p. 121, tab. 1, fig. 1. 
 
 3 I ought to mention here that the growth and development of the bladder-worms are 
 by no means alike in all cases. Not only do the different organs infested induce numerous 
 
HISTOLOGICAL DIFFERENTIATION OF THE EMBRYO. 
 
 341 
 
 smaller, and measures not more than about 01 mm. Embryonic 
 
 hooks cannot, therefore, be demonstrated with any certainty. A 
 
 histological differentiation now 
 
 sets in, and is inaugurated by a 
 
 clearing up of the central portion 
 
 of the body-mass. This is due 
 
 to large, clear, non- granular 
 
 vesicles, which have an almost 
 
 drop-like appearance, and which 
 
 grow so rapidly that the inner 
 
 parenchyma is soon seen as a 
 
 distinct tissue, different from the 
 
 FIG. 182. A piece of a rabbit's liver with 
 
 In the Second bladder-worm passages (Cysticercus pisiformis) 
 ( x 10). 
 
 cortical layer. 
 
 week one can distinguish in the 
 
 worm, which has now grown to 0'5 mm. or more, the first traces of 
 
 the subsequent musculature through the not inconsiderably thickened 
 
 cuticle. These are in the form of fine fibres, which run in close 
 
 groups in two directions at right angles to one another; the outer 
 
 are the circular, the inner the longitudinal fibres. In appearance and 
 
 arrangement they resemble the subcuticular musculature of the adult 
 
 Cestodes (p. 290). 
 
 One must not suppose that the worms 
 could not move before these muscular fibres 
 were distinguishable ; in fact, the form of the 
 body is seen to change, constricting itself here 
 and there, the contractions passing peristalti- 
 cally up or down. The motions are, indeed, 
 weak and slow, but even the musculature is 
 not able at first greatly to accelerate them. 
 
 The cortical layer, running under the sub- 
 cuticular muscles, consists of small, closely 
 pressed nucleated cells, with numerous shining, 
 fat-like molecular bodies often grouped to- 
 
 ,, XT ,, ,, , . , FIG. 183. Cysticercus pisi- 
 
 gether. Next there are the above-mentioned formis before the deve- 
 drop-like vesicles, which have between them a lopment of the head, with 
 
 . J . . .. granular sheath and cyst 
 
 clear, sparsely developed substance, and are ( x 60). 
 considerably larger than in the former stage. 
 
 But after a short time the cortical layer undergoes a further 
 differentiation. The cells, of the deeper layer at least, form a clear, 
 tough, connective tissue mass, penetrated by numerous cross muscular 
 
 variations, as may be strikingly seen by comparing the young bladder-worms of the 
 brain (Cysticercus cellulose?) with those found in the muscles, but even in the same organ 
 we usually find bladder- worms of diverse size and differentiation. 
 
342 THE DEVELOPMENT OF CESTODES. 
 
 fibres. Near the cuticle the cells at first retain their original nature ; 
 but after the formation of the head they also change, stretching them- 
 selves out, and finally becoming for the most part the subcuticular 
 spindle-cells which we have already studied. 
 
 As to the arrangement of the muscle fibres, they are most easily 
 understood by reference to later stages. One can distinguish two 
 kinds of fibres thicker and thinner. The former lie deeper, and are 
 grouped together internally to the cortex as a loose, much interrupted 
 sheath. The fibrils, on the other hand, form a network with cubical 
 meshes, which penetrates the cortex and becomes connected with 
 the processes of the subcuticula. It is, however, doubtful whether 
 these two kinds of fibres form two distinct systems, for the thicker 
 fibres not only split and branch, but are at many places directly 
 continued into the network of fibrils. 
 
 While the differentiation of the cortical layer is progressing, the 
 young cystic worm begins to excrete that watery fluid, whose presence 
 has originated the name " bladder- worm," and given occasion to the 
 theory of " dropsical " worms. I am not able to express a decided 
 opinion as to the exact nature of this process, to say whether it results 
 from the flowing together of the interstitial cells, or from the accumu- 
 lation of the lymph among the parenchyma ; yet from my observations 
 of Cysticercus pisiformis I am inclined to adopt the former theory. 
 This bladder-worm differs from its allies in this, that it is only at a 
 subsequent stage, when about four weeks old and from 4 to 5 mm. 
 long, that it becomes a true bladder- worm. Till then it is wholly 
 parenchymatous, filled internally with a mucous tissue, with large 
 vesicles, which is hardly at all sharply distinguished from the cortical 
 layer, but is, like it, penetrated in various directions by muscular 
 fibres. In this form I was able to convince myself that the fluid first 
 collected in vacuole-like spaces, which became ever more distended, 
 and finally flowed together. The interstitial tissue was, of course, 
 thereby destroyed, so that one could often observe how the muscular 
 fibres projected more or less into the water-tilled space, either freely 
 or with attached shreds. 
 
 An indirect proof of the correctness of this theory is also, I think, 
 to be found in the fact that in the ordinary Cysticerci, where the ex- 
 cretion takes place very early (in some when they hardly measure 
 0*3 mm.), and is much more copious than in Cysticercus pisiformis, the 
 bladder-like body consists solely of the above-described cortical layer. 
 The accumulation of fluid has therefore gone on at the expense of 
 the former internal substance. A specially formed border sheath is 
 in such cases wanting, the inner surface of the subcuticular connec- 
 tive substance being itself directly washed by the fluid. 
 
PARENCHYMATOUS BLADDER-WORMS. 
 
 343 
 
 The state of matters in Cystitercu* pisiformis further shows us 
 that the excretion and accumulation of fluid in the interior of the 
 bladder- worms do not by any means always occur in the same com- 
 plete fashion. I have lately come to know of a number of Cysticerci 
 which had, strictly speaking, no bladder, since the accumulation of 
 water had either never occurred, or only to an extremely small extent. 
 They were all tape-worms without hooks, but I was unfortunately 
 unable to identify them. One of these forms is probably identical 
 with Diesing's Piestocystis varidbilis (Fig. 184). I observed it in the 
 lungs of the crow only once indeed, but in tolerable abundance. 
 
 FlG. 184. Longitudinal 
 section of an unarmed cystic 
 worm from the lung of the 
 crow (Piestocystis variabilis, 
 Diesing?) (x 30.) 
 
 FIG. 185. Unarmed cystic worm from the 
 body-cavity of Lacerta vivipara (Piestocystis 
 Dithyridium, Diesing). A, with head in- 
 vaginated ; B, with head half extruded ; 
 C, with evaginated head. ( x 30.) 
 
 The bladder has an extremely thick wall, and is filled internally with 
 a mucous tissue which surrounds the narrow bladder-cavity on all 
 sides. Two other allied forms one from the sub-epidermal tissue of 
 the nightingale, and another (Fig. 185) from the body-cavity of Lacerta 
 vivipara (Piestocystis Dithyridium, Diesing) are wholly destitute 
 of a bladder-cavity. The interior of the body consists of an interlaced 
 connective substance, which is only so far variable in that its con- 
 sistency decreases towards the centre. With the loss of the bladder- 
 cavity, most of the characteristic peculiarities of the bladder-worms 
 have been also lost, so that it is hardly possible to distinguish these 
 forms fronf developed bladder-worms with evaginated heads. In 
 fact, even in spite of the attached caudal bladder, such a form as that 
 represented on Fig. 185, C, looks exactly like a young, still unseg- 
 mented tape-worm. 
 
344 THE DEVELOPMENT OF CESTODES. 
 
 Almost contemporaneously with the differentiation of the cortical 
 cells, a new formation occurs in the peripheral tissue. In some way 
 not clearly understood, there arises in that region what we have 
 already discussed in the adult tape-worm as the excretory system. 1 
 Here and there one observes a clear, usually stellate, finely branched 
 streak, in which one can afterwards detect the parts of a vascular 
 network which surrounds the whole bladder, and rapidly attains a 
 considerable development. But before the formation of the head, it 
 is not possible to distinguish longitudinal and transverse vessels ; it is 
 simply a network with meshes of varying size and diverse arrange- 
 ment. From the larger stems, there spring numerous fine branches 
 ramifying like a tree, which apply themselves to the surface of the 
 bladder, and pass between the fibrils into a second finer network (see 
 Fig. 199). No communication with the watery internal space is 
 observable. On the other hand, we can recognise in the peripheral 
 vessels the same ciliated apparatus which we noted in the vascular 
 system of the adult Cestodes. They are exceedingly numerous in 
 Cysticercus pisiformis, and are in continual undulating motion. I 
 have not been able to decide whether the cilia are seated on the 
 ordinary walls of the vessels, or on special funnels appended to 
 the vessels, and in connection with cavities in the connective sub- 
 stance. 2 The latter is supposed to be true in the case of young Dis- 
 tomes. At any rate this apparatus in the bladder must have the 
 same significance as in the adult Cestodes. The resemblance becomes 
 still more complete when we learn from Wagener that the vascular 
 system even in the bladder- worm communicates with the exterior by 
 means of a short contractile tube at the posterior pole. 
 
 I have been able to convince myself of the existence of this ter- 
 minal funnel only in the above-mentioned hookless Cysticercus from 
 Lacerta vivipara (Fig. 1 85). It is clad with a thickish cuticle, pro- 
 bably resulting from an invagi nation, and leads to two (or four?) 
 vessels which ascend to the head at some distance from the surface, 
 and give off in their course numerous lateral branches. 
 
 The young bladder-worm persists for a while as a simple more or 
 less spherical watery bladder, until the formation of the subsequent 
 tape-worm head inaugurates a new epoch. In Echinococcus this takes 
 place only after several months, when the bladder has grown to per- 
 haps the size of a nut ; in the Ccenurus it occurs in the fifth week, 
 when the worm is as large as a pea; in the Cysticercus proper it 
 
 1 In my monographs on cystic worms, I erroneously referred the appearance of this 
 vascular system in Cysticercus pisiformis to a later developmental stage. 
 
 2 Biitschli, " Bemerkungen iiber den excretorischen Gefassapparat der Trematoden, " 
 Zool. Anzeiger, Jahrg. ii, p. 588, 1879; see also the first German edition of this work, 
 Bd. i., p. 766. 
 
MOULTING OF THE YOUNG BLADDER-WOKM. 345 
 
 appears still earlier, usually in the course of the third week, when the 
 bladder is hardly 1 mm. in size, if so much. Only the bladder-worm 
 of the rabbit attains at this time to a length of more than 2 mm. 
 (cross diameter = 04 mm.), having at an early stage changed from 
 a globular to an extended form. 
 
 The first trace of the head is seen in the subcuticular layer of 
 cells the most important layer in the formative history of these 
 organisms. At a distinct point which we may call the anterior pole, 
 and which is easily recognisable as such in extended forms like Cysti- 
 cercus pisiformis, an active vegetative process sets in. In conse- 
 quence of this, the cellular layer becomes thickened into a meniscus, 
 which soon forms a little protuberance, and grows ever further inwards 
 into the bladder-cavity or the substance which fills it. 
 
 As soon as this has gone on for some little time, a pit-like depres- 
 sion arises on the outer covering of the body, which increases in depth 
 as the protuberance grows, and finally broadens out at its lower portion 
 into a bottle-shaped cavity. The rudiment of the head is thus not 
 solid, but hollow, and its cavity is to be regarded as an invagination 
 from without, especially since the cuticle of the bladder is continued 
 inwards through the outer opening, and completely lines the interior. 
 
 FIG. 186. Young bladder-worms of FIG. 187. Young bladder-worms of T. 
 
 Tcenia saginata. ( x 30.) serrata, with rudiment of head. ( x 12.) 
 
 During the deepening process, the lining envelope is sometimes changed. 
 I have seen bladder-worms in which two or three discharged cuticular 
 membranes lay like conical shells one within the other. At this 
 stage, too, one can directly observe the new formation of the cuticle 
 over the bladder, and this much more distinctly than afterwards, 
 since in these young forms the old skin is usually discharged as a 
 continuous sheath, and remains lying for a while near the body. It 
 is loose and thick, and therefore quite different from the thin new 
 cuticle lying below. 
 
346 THE DEVELOPMENT OF CESTODES. 
 
 The substance of the newly formed head consists of the same 
 small nucleated cells which we found in the subcuticular sheath, 
 whence, indeed, it originated. As soon as it begins to raise itself 
 more prominently, and to grow out like a clapper, one can see on the 
 surface turned towards the bladder-cavity a thick envelope of a fibrous 
 character. The head of the bladder-worm is, in other words, enclosed 
 in a sac which separates it from the rest of the body, and which can 
 still be recognised as a special formation when the enclosed cells have 
 completed their metamorphosis. I have proposed for this envelope 
 the name "receptacle" 1 (receptaculum scolecis), and am still inclined 
 to support this proposal, although I have meanwhile come to hold a 
 
 FIG. 188. Various stages in the formation of the head of Cysticercus cJluLotce t 
 showing the receptacle. ( x 45.) 
 
 different opinion as to the nature of the organ in question. I was 
 formerly of opinion that this receptacle originated from a differen- 
 tiation of the cellular mass of the head, and was indeed genetically a 
 part of the head, but I have subsequently become convinced that it 
 belongs to the inner layer of muscular fibres which run inside the 
 bladder, and which are pushed into a sac by the elevation of the head, 
 the cells of which have a more peripheral position. Of course, one 
 must not suppose from this statement that the receptacle is simply 
 formed by a distent ion of the inner layer of muscles, and that it only 
 contains the muscular fibres which formerly overlaid the cellular rudi- 
 ment of the head. On the contrary, there can be no doubt that new 
 elements become associated with these old muscular fibres during the 
 
 1 Von Siebold has also used this term in his work on tape-worms and bladder-worms, 
 but in quite another sense, namely to denote the proper body of the bladder- worm (the 
 enlarged six-hooked embryo). Kuchenmeister also speaks of a receptacle in the new 
 edition of his work on Parasites (p. 61), but understands by the term the primitive rudi- 
 ment of the head, which he does not recognise as such, but regards as a brood capsule, 
 which subsequently bears the tape-worm head. Indeed the description he gives of the 
 development of the bladder-worm is such a strange mixture of capricious imagination and 
 confused representation, that I must decline entering into its details. 
 
THE RECEPTACLE AND ITS ANATOMICAL RELATIONS. 
 
 347 
 
 elevation and growth of the head, or, in other words, that the receptacle 
 is formed by further differentiation of the muscular layer of the 
 "bladder, just as the head proper is formed from the suhcuticular 
 sheath. Nor can the receptacle and head be distinguished so sharply 
 from one another as is at first apparently the case. As the muscular 
 sheath and the cellular layer are bound together in the wall of the 
 bladder, so we can always demonstrate a connection between the 
 receptacle and its contents (Fig. 197), a connection which extends 
 over the whole surface, or is in some species confined to certain 
 points. 
 
 Thus the receptacle is not in every case an equally independent 
 structure. It has least independence in the bladder- worms with paren- 
 chymatous bodies, such as we have seen in Cysticercus (Piestocystis) vari- 
 dbilis and its allies, for there it is 
 not only connected with the mass 
 of the head, but is, like the ordi- 
 nary body muscles, bound up with 
 the tissue of the bladder. One 
 can observe how the muscular 
 sheath which runs between the 
 cortex and the inner parenchyma 
 (Fig. 19 7) bends backwards at the 
 anterior end, and surrounds the 
 head as a sac, and how the in- 
 dividual fibres Often Separate FIG 189. -Cephalic end of a young bladder- 
 
 worm from the rabbit, showing the still im- 
 themselves from the receptacle, perfectly developed hooks. ( x 45.) 
 
 and mingle with the parenchyma. 
 
 The state of matters is very similar in Cysticercus pisiformis where 
 the bladder- worm body preserves anteriorly its original parenchyma- 
 tous character, so that the receptacle is united on all sides to a loose 
 connective substance. The only difference which can be observed is 
 that the fibres of the receptacle are more closely appressed and more 
 firmly interwoven. 
 
 Where the inner parenchyma is wholly obliterated by the accumu- 
 lating water, as in the majority of true bladder- worms, the receptacle 
 of course acquires a distinct external boundary. The connection with 
 the body of the bladder becomes in such cases restricted to the basal 
 portion of the head, where one can observe the fibres passing directly 
 into the muscular sheath. 
 
 As a rule, however, it is only the exterior surface of the receptacle 
 which attains this independence ; for the inner surface remains usually 
 in general, though, as we shall afterwards see (Fig. 197), in loose 
 connection with the head. The bladder- worm of Tcenia solium, the 
 
348 THE DEVELOPMENT OF CESTODES. 
 
 so-called Cysticercus cellulosce, is almost the only instance of another 
 state of affairs. There the receptacle is separate from the head, and 
 becomes a sac-like envelope, wholly free except at a restricted region 
 posteriorly. This peculiarity is connected with the fact that the head 
 of this bladder- worm, instead of growing in proportion to the receptacle, 
 as is usually the case for a lengthened period, becomes rapidly and 
 considerably elongated, and is at an early stage bent like a knee inside 
 the sac (Fig. 188, C). 
 
 The head remains in this state till it acquires a length of perhaps 
 a millimetre. This growth is accompanied only by histological 
 changes. These are most striking in the neighbourhood of the cuticle 
 which clothes the interior of the head, and which afterwards becomes 
 the cuticular covering of the head of the tape -worm. Here, at 
 a position which corresponds to the subcuticular sheath, the 
 hitherto indifferent cellular mass assumes very early a radiate struc- 
 ture (Fig. 188, A). This is brought about by the cells growing out 
 into a layer of closely appressed radiate fibres. These are the struc- 
 tures which we described in the tape-worm (p. 288) as subcuticular 
 fibre-cells. At first sight one might regard them as epithelial cylin- 
 drical cells. Indeed they seem to have the epithelial structure of the 
 subcuticula; but this appearance is quite deceptive. The close 
 grouping, which makes them look like a cellular layer, is caused by 
 the absence of an interstitial connective tissue. When this is subse- 
 quently developed, one can recognise the truth of our position, and 
 that more clearly in the bladder-worm than in the adult form. To be 
 undeniably convinced of the true nature of the subcuticula, it is 
 sufficient to make a thin section of the swollen pad of connective 
 tissue on the head of a Ccenurus, or on the bladder of Cysticercus pisi- 
 formis, which is further penetrated by an extraordinary number of 
 distinct cross fibres. 
 
 As soon as the subcuticula acquires this radiate structure the adja- 
 cent cells of the head begin their histological metamorphosis. For the 
 most part at least they become extended, and grow into fibres, which, 
 in spite of the still distinct nucleus, are undeniably muscular fibres. 
 The course and direction of the fibres are at first indistinct, gradu- 
 ally, however, they become better defined, those next the subcuticula 
 assuming a longitudinal direction, those further outwards becoming 
 rather transverse. Of course this applies only to the main bands, for 
 there are many deviations in detail. 
 
 At this time the rudiments of the vascular system appear. One 
 can recognise four longitudinal stems which spring at the insertion of 
 the head from the vascular system of the bladder, run downwards to 
 the outside of the longitudinal fibres, and become at the wider end 
 
THE DEVELOPMENT OF THE HEAD. 
 
 349 
 
 FIG. 190. Head of Cysticercus pisi- 
 formis, with vascular system. ( x 45.) 
 
 united by a circular vessel into a connected system. Afterwards one 
 can observe the formation of a number 
 of fine twigs, with ramifying processes 
 and ciliated organs. 
 
 At the same time the first cal- 
 careous bodies make their appearance, 
 and that primarily and principally at 
 the point from which the head springs, 
 whence they spread in ever-increasing 
 numbers. Occasionally a few of these 
 concretions are to be found even 
 before this round about the head. 
 The body of the bladder is, as a rule, 
 but sparsely supplied with them, 
 though there are exceptions, such as Piestocystis. 
 
 In order to understand the further development of the head in the 
 tape-worms, one must imagine it as a cylindrical structure, not solid, 
 as it appears, but with a blind cavity running up its whole length. 
 If we suppose this head to pass posteriorly, not into the jointed body 
 of the adult tape-worm, but into a hollow bladder, into which it is 
 indeed iiivaginated, then we have a representa- 
 tion of the primitive state of head in the bladder- 
 worms we are discussing (Fig. 191). The surface 
 of the rudimentary head next the receptacle 
 represents the subsequent inner parenchyma, 
 while the future outer surface, with the cuticle, 
 lines the cavity of the clapper-like rudiment. 
 The tape -worm head thus originates within the 
 bladder, as Goze, and Wagener after him, 
 observed, and occupies an " inverted position." 
 
 One is most distinctly convinced of tin's 
 arrangement by noting the formation of the 
 suckers and hooks which generally appear soon 
 after the first rudiments of the head are formed. They are first seen 
 at the distended lower end of the bottle-shaped cavity, the circle of 
 hooks lowermost, the suckers somewhat higher where the cavity is 
 widest. 1 Their relative position is therefore the reverse of the 
 final one, where the hooks are on the apex above the suckers. 
 
 1 With this agree the results of van Beneden on the development of Cysticercus pisi- 
 formis, as detailed in his " Vers intestinaux," p. 238, 1858. Moniez, however, describes 
 an entirely different mode of formation. I shall afterwards return to the discussion of his 
 theory, but will only here remark that I have repeatedly and most distinctly convinced 
 myself of the truth of my statements. 
 
 FIG. 191. Head of 
 Cysticercus piniformis just 
 mature, (x 40.) 
 
350 
 
 THE DEVELOPMENT OF CESTODES. 
 
 Thus we understand how it is that, in transverse sections of the 
 lower part of the rudimentary head (Fig. 192), we come upon some 
 
 where the four suckers are seen all opening 
 into the central space. Such a section must 
 of course be above the hooks. I ought also 
 to mention that one frequently finds cases 
 where the apical surface is pushed out- 
 wards, 1 so that the hooks (Fig. 193) come 
 to be about the same level as the suckers. 
 I 'believe that this occurs especially in 
 specimens which have been suddenly 
 killed by spirit, &c., while in full posses- 
 sion of their powers of contraction. 2 
 Although this pushing outwards occa- 
 sionally occurs early, even before the 
 formation of the hooks (Fig. 188, O), I 
 think it is to be regarded as the result only of a secondary alteration, 
 probably determined by a contraction of the surrounding musculature. 
 
 FIG. 192. Transverse section 
 of the anterior end of the bladder- 
 worm of the rabbit, at the level 
 of the suckers, (x 40.) 
 
 FIG. 193. Longitudinal section through the head of a bladder- worm from the 
 rabbit, where the crown of the head is pushed outwards. ( x 60.) 
 
 Before passing to describe the metamorphoses of the head, I may 
 remind the reader that the cavity is widened out at the lower end, 
 which, as the embryo grows in length, becomes ever more sharply 
 
 1 The original here has " inwards " (nach Innen), referring to the cavity of the in- 
 vaginated head. I think it better to use the word " outwards," meaning " towards the 
 periphery of the bladder." W. E. H. 
 
 8 I infer this from the fact that in my earlier investigations, which were mostly on 
 living specimens, this appearance but rarely occurred, while I observed it frequently when 
 working with hardened specimens. 
 
DEVELOPMENT OF THE SUCKEES AND HOOKS. 
 
 351 
 
 distinguished from the other more canal-like portion. It is this lower 
 enlargement which is the seat of all those processes which give the 
 head its characteristic form, and which are at this time (in Cysticercus 
 pisiformis in the course of the fourth week) progressing, so far at least 
 as suckers, hooks, and rostellum are concerned. 
 
 The formation of the suckers is most striking. It is introduced by 
 a change in the form of the inner space, which is produced inwards 
 to form little pockets in the substance of the head- walls ; these 
 occur at four points, at equal distances from one another. They 
 become more and more markedly distinct from the rest of the in- 
 ternal space, and represent, of course, the cavities of the suckers. The 
 musculature, which forms such an important part of the apparatus, 
 then arises (Fig. 195) ; the subcuticular sheath, with its radiately 
 arranged cells, surrounds each pocket like a hood, and becomes an 
 independent structure, in which the characteristic arrangement of the 
 muscular fibres very soon appears. The fact that the radiate fibres, 
 which form the greater part of the musculature, arise from the subcu- 
 ticular cells, seems to be in favour of the opinion which we have more 
 than once expressed, that the latter have a closer connection with 
 the muscular than with the epidermal tissue. 
 
 The rostellum originates in a closely analogous fashion. The sub- 
 cuticular tissue at the bottom of the head-cavity (i.e., in the depression 
 between the suckers) which is, as we have seen, occasionally pushed 
 forward into a sort of boss (Fig. 196) forms a cushion (Fig. 194), which 
 is supplied with muscles by the development of the above-mentioned 
 extended cells. 
 
 FIG. 194. FIG. 195. FIG. 196. 
 
 Metamorphoses of the bead of Cysticercus pisiformis. ( x 45.) 
 
 The hooks arise round about the rostellum, or rather on a small 
 circular ridge 1 which surrounds it (Figs. 194, 195). While the hooks 
 
 1 Later observations force me to modify in some particulars the account I previously 
 gave of the history of the circular ridge (first German edition of this work, Bd. i., 
 p. 245). 
 
352 
 
 THE DEVELOPMENT OF CESTODES. 
 
 are gradually becoming mature (for it is only in the bookless Tcenia 
 saginata tbat the original state persists), this ridge grows further and 
 further over the rostellum, until (Fig. 189) its margins coalesce in the 
 centre, and form the layer in which the posterior x processes of the 
 hooks are embedded (see Fig. 151). The metamorphosis of the hooks 
 themselves has been already described (p. 287). They appear first 
 as soft, thin, little cones, which grow into the cavity of the head with 
 their points upwards and their concave sides turned outwards. Be- 
 fore they become elevated, one finds countless fine points on the 
 periphery of the subsequent rostellum, some of which grow directly 
 into the cones, while the greater number of them speedily disappear. 
 
 FIG. 197. Head and body of 
 Ccemirut, in situ. ( x 100.) 
 
 FIG. 198. Cysti- FIG. 199. Head and 
 cercuipi*iformi8\viih body of Cysticercus 
 head half evaginated. pisiformit in com- 
 (x6.) pletely evaginated state, 
 
 (x 19.) 
 
 The histological differentiation is in the majority of cases complete 
 towards the end of the second month. The head has then essentially 
 its adult organisation, 2 and almost its adult size, although it still 
 
 1 The " posterior process of the hook " is the one directed towards the apex of the 
 head. W. E. H. 
 
 4 I may briefly note that one can already recognise under the rostellum the " plate-like ' 
 muscles described by Nitsche (Zcitschr. f. uriss. ZooL, Bd. xxiii., p. 181, 1880), and in 
 successful sections the head ganglia. The latter are widely separated from one another by 
 the pressure which acts longitudinally on the head, so that they have the greater part of 
 the rostellum lying between them. 
 
EVAGINATION OF THE HEAD. 353 
 
 remains inverted in the maternal bladder (Fig. 191). But the develop- 
 ment of the bladder-worm is not yet quite complete. The head, 
 which was at first only a little distant from the bladder-wall, becomes 
 ever further removed by the elongation of its basal portion ; thus there 
 arises in course of time a distinct vermiform body, extending in 
 cylindrical form between the upper narrow neck-like portion of the 
 head and the bladder. Both head and body lie still within the 
 receptacle (Fig. 197). The succession of layers corresponds with that 
 of the head ; the surface covered with cuticle is inwards, next the 
 cavity. The musculature is more strongly developed than in the 
 head, and the number of calcareous bodies is usually very con- 
 siderable. 
 
 The older the bladder-worm, the more this body grows ; it acquires 
 numerous cross wrinkles and folds, which usually extend far into the 
 canal-like space, and it squeezes itself together in the extended recep- 
 tacle as far as the space will permit. As a rule, the head takes up a 
 lateral position which we have already noted in the bladder-worm 
 of the pig as a natural consequence of the growth in length and 
 early bending of the head (p. 346). The connection with the receptacle 
 presents no special difficulty in the way of this change of position, 
 for the connective substance which has been produced is soft and 
 extensible, and permits many alterations (Fig. 197). If the receptacle 
 be unable completely to contain the contents, then the end of the body 
 which is next the bladder is extruded (Fig. 198) from the opening 
 of the head-cavity, so that the former inner surface comes to be 
 external. Sometimes the whole of the body and head are thus evagi- 
 nated, so that the bladder-worm becomes (Fig. 199), indeed, like a 
 tape-worm with an incompletely jointed body and an attached 
 " caudal bladder " (Tcenia msceralis). 
 
 In this evagination the musculature of the bladder has probably a 
 share as well as that of the receptacle. The pressure which the former 
 can exercise affects primarily only the enclosed fluid, but this is trans- 
 mitted in all directions, and is finally most influential where the 
 resistance is least namely, at the position of the evaginating head. 
 The process is essentially the same as we formerly (p. 311) described 
 in the protrusion of the penis from the so-called " cirrhus-pouch," 
 which stands to the cirrhus in much the same relation, even anatomi- 
 cally, as the receptacle to its contents. The retraction of the protruded 
 structure can of course be effected only by special muscles. 
 
 Though the whole head-mass of the cystic worm has been evaginated, 
 this does not prevent some of the individual parts remaining intro- 
 verted. This is particularly true of the head proper, which protrudes 
 (Fig. 193) from the bottom of the appendage, and not unfrequently 
 
 z 
 
354 THE DEVELOPMENT OF CESTODES. 
 
 pushes itself forwards even into the cylindrical body. In this way 
 the cuticular coat conies to lie externally, and the suckers are found 
 Flo 200 FlG 201 under the hooks. When this eleva- 
 
 tion is complete, as in Fig. 20 1, 1 
 then the head is in position and 
 character like the subsequent tape- 
 worm head, and that the more since 
 the inner surfaces, formerly external, 
 soon come into close contact, and 
 form an apparently solid mass. 
 
 Such appearances have often 
 given rise to the supposition that 
 the bladder-worm had this position 
 
 FIGS. 200 and 201. Rudimentary and form from the very first. Ac- 
 heads of Tcenia serrata at the beginning , . , , . , , , 
 
 (Fig. 200) and at the end (Fig. 201) of cording to this theory, what we 
 the protrusion of the head. ( x 20.) have above described as the rudi- 
 mentary head, and have followed in its metamorphosis step by step, is 
 only a sheath, from the base of which the head subsequently arises as 
 a solid projection. 
 
 Moniez, the last author who has discussed the Cysticerci, believes 
 he has convinced himself of the truth of this by sections, and ex- 
 plains my opposing, and as he thinks erroneous, results by referring 
 them to my imperfect methods of investigation. It is, of course, true 
 that I first reached these results from the examination of squeezed 
 preparations (1856), but I did not neglect to corroborate them by means 
 of sections when our methods became more perfect. These later obser- 
 vations lead me still to persist in upholding the accuracy of the above 
 outlines, in spite of Moniez's opposition. Moniez has obviously confined 
 his observations mainly to old bladder-worms (Cysticercus pisiformis), 
 whose heads have often, as we have noted, lost their original position, 
 and are therefore unfitted to lead one to a true understanding of the 
 mode of origin. The young forms of which he made sections were, as 
 I could see from his preparations, at a stage when the head and its 
 cavity had still but a somewhat undifferentiated formation. 
 
 What Moniez considers as the beginning of the head is only a 
 boss-like swelling of the base, such as (see Fig. 196) one not unfre- 
 quently finds in violently killed bladder- worms. Far from represent- 
 ing the whole head, this projection is, as we have seen, neither more 
 nor less than its apex with the lenticular rostellum, which, when there 
 is no protrusion, is seen in the form of a meniscus (Fig. 194), with 
 incurved anterior surface. If Moniez had investigated the proper 
 stages, he would have been convinced that the suckers, instead of being 
 
 1 The figure is copied from a preparation kindly lent to me by M. Moniez. 
 
SIZE AND FORM OF BLADDER- WORMS. 355 
 
 formed at the base of the protrusion, arise above it on the side walls 
 of the bottle-shaped enlargement, and at first appear as pocket-like 
 invaginations, which afterwards become clad with the above-described 
 muscular wall. He would, in other words, have been convinced that 
 it is the primitive head rudiment which is changed into 
 the tape-worm head at first necessarily invaginated. x 
 Besides, even the adult bladders often show in the position 
 of the head traces of the original state, so that one is in 
 no way warranted in regarding the protrusion as a normal 
 or necessary developmental stage. 
 
 This is true, indeed, only of the majority of cystic 
 worms, but specially of those in which we are now 
 interested. There are, however, exceptions, as for instance 
 the familiar bladder-worm of the mouse (Cysticercus 
 fasciolaris), which becomes Tcenia crassicollis in the in- 
 testine of the cat. In this animal the cylindrical body, 
 which is in other cases hardly ever more than a few milli- 
 metres long, gradually grows to a length of several centi- 
 metres. The receptacle is unable to contain so large a 
 body, and thus the latter comes to be evaginated along 
 with the head at quite an early stage. In this condition FlG - 202. 
 
 . . , . ,., ,. ,, Custwercus 
 
 it persists, and is so like an ordinary tape-worm that its fasciolaris 
 cystic nature escaped detection for a long time. In spite ( nat size )- 
 of this resemblance, the jointed body of this bladder- worm does not 
 pass into the subsequent tape-worm body any more than any other 
 bladder-worm body does. 2 
 
 Mature bladder-worms differ greatly in size and form, as we shall 
 afterwards see. Here we shall only mention that among common forms 
 the smallest is Cysticercus fasciolaris, and C. tenuicollis (the bladder- 
 worm of Tcenia marginatd) the largest. In the former the bladder is 
 usually not so large as a pea, while in the case of the latter it grows 
 occasionally to half a foot in length or more. 
 
 1 My supposition is corroborated by Moniez's own statement ("Essai monographique 
 sur les Cysticerques, " Travaux de VInstitut. zoolog. de Lille, t. iii., p. 41 : Paris, 1880), 
 that he has only imperfectly followed the metamorphosis of the head. He seems to have 
 missed just the decisive stages. None the less did he hesitate at once to condemn my 
 results. According to him, what we have called the head-rudiment is only the cradle of 
 the future head. It is a part of the bladder, arising by invagination, and forming the 
 receptacle ; for what I have described as the receptacle is no special organ, but only an 
 outer muscular layer. I must, however, refrain from entering into a discussion of Moniez's 
 statements, and only remark that I cannot concur with the histological results any more 
 than with the developmental. 
 
 2 In the first German edition of this work I held the contrary opinion, which was 
 based on error, as I have long since pointed out in the case of Cysticercus fasciolaris 
 (Zeitschr. f. wiss. ZooL, Suppl.-Bd. xxx., p. 605, note, 1878). 
 
356 THE DEVELOPMENT OF CESTODES. 
 
 In the great majority of species the productive power of the 
 bladder is exhausted in the formation of a single tape-worm head, as 
 in the bladder-worms proper, which were referred to the genus Cysti- 
 cercus by the older Helminthologists. The cause of a multiplication of 
 heads is unknown ; therefore, we can hardly say that it is not possible 
 for a Cysticercus to have at a time two or three heads, instead of only one, 
 and isolated instances of polycephalous bladder- worms have indeed been 
 chronicled, 1 though my observations on Cysticercus longicollis of the 
 shrew (Hypudceus), (the young stage of Tcenia crassiceps of the fox), to 
 which most of these reports refer, have caused me to regard these 
 alleged instances with some suspicion. 2 The lappet-like appendages 
 of the caudal bladder, which have been regarded as new heads, turned 
 out to be simple diverticula of the bladder, that is to say, they owed 
 their origin to an irregular growth, determined perhaps by pressure 
 or traction. It seems to be very likely that these structures have a 
 mechanical cause, 3 since I once saw in Cysticercus pisiformis a similar 
 diverticulum firmly connected with the enveloping connective tissue 
 capsule, and since the bladder-worms of the common Tcenia of man 
 often grow out into irregular tubes in the subarachnoidal spaces of 
 the brain, which, with their adherent bladders, sometimes have a quite 
 racemose character, but yet never form new heads. 
 
 This polycephalous condition, at most an exception in the Cysticerci, 
 occurs constantly in the "stagger-worm" of the sheep; that is, in the 
 cystic stage of the Tcenia ccenurus of the dog. In this bladder-worm, 
 which is found in the cavities of the skull, a group of three or four 
 heads is present from the first, and the number is continually increased 
 up to several hundreds. The new heads are 
 budded out beside and between the older, and are 
 not irregularly scattered over the whole surface of 
 the bladder, but occur in groups, and only in one 
 (anterior ?) segment of the vesicular body. 
 
 The Ccenurus (Tcenia multiplex of Goze) is 
 related to the Cysticercus as a compound to a 
 simple animal a sufficient reason for systematic 
 FIG. 203. Heads of zoologists to separate them. But apart from the 
 multiplication of these heads, the structure is the 
 same. Each of these many heads arises just as the single one did 
 (Fig. 197) ; in origin and structure they are quite analogous. Nor 
 can we regard it as a special characteristic of the Ccenurus that the 
 
 1 Especially by Bendz in Olcen's I sis, p. 814, 1844. 
 
 2 V. Siebold comes to a similar decision, Zcitschr. f. wiss. Zool., Bd. ii., p. 226, 1880. 
 
 3 The "double monster" of Cysticercus longicottis, figured by Bremser in his " Icones 
 Helminthum" (Tab. xvii., Fig. 14), is probably to be regarded as due to the above cause. 
 
THE PROLIFERATION OF ECHINOCOCCUS. 357 
 
 bladder has often an irregular, more or less diverticular form. This is 
 particularly well seen in those worms which are found outside the 
 cranial cavity, and which are partly perhaps separate species. Some- 
 times their regular sinuses present an almost racemose appearance, 
 like the the so-called Cysticercus racemosus.* 
 
 In the case of the familiar Echinococcus, which originates from the 
 Tcenia echinococcus living in the intestine of the dog, the state of affairs 
 is somewhat different. We shall afterwards have an opportunity of 
 studying these wonderful structures more closely, and will only now 
 summarise what is necessary in order to understand their relation to 
 other bladder-worms. 
 
 Echinococcus is, like Ccenurus, polycephalous, but its heads differ 
 not only in their minute size and myriad numbers, but also in their 
 relations to the body of the bladder. For, instead of springing directly 
 from it, as has been hitherto the case, they originate on the wall of 
 special brood-capsules which lie in numbers on the inner wall of the 
 bladder. 
 
 FIG. 204. Brood-capsule of Echinococcus, FIG. 205. Diagrammatic represen- 
 
 with adherent heads in various stages of tation of a proliferating Echinococcus. 
 
 development. ( x 36. ) 
 
 The size of these brood-capsules never exceeds 1/5 to 2 mm. in 
 diameter, and even this size is attained only by the oldest capsules, 
 which enclose a dozen or more heads. At first the capsule contains 
 only a single head, but the number gradually increases, new heads 
 being continually budded off from the walls. The process of forma- 
 tion closely resembles that of the head of Cysticercus. A diverticulum 
 of the outer surface occurs, which grows out into a hollow caecum, 
 forming the tape-worm head, as in the ordinary bladder- worm. The 
 completed head then draws itself back into the cavity of the brood- 
 capsule, so that the suckers and hooks become ensheathed by the 
 former neck, and the originally club-shaped appendage now lies like a 
 berry on the inner wall of the capsule. Sometimes this invagination 
 
 1 A striking instance of this has been lately described and figured by Megnin, Journ. 
 Anat. et PhysioL, PL vii., 1880. See also Bendz, "Om Oprindelsen af Dreiesygen hos 
 Faaret," Tidsskrlft for Landoekonomie, July 1857, a memoir which has remained to all 
 appearance unnoticed. 
 
358 THE DEVELOPMENT OF CESTODES. 
 
 occurs at an earlier stage, even before the formation of the head has 
 begun, and then it is complete up to the blind end of the caecum. The 
 metamorphosis of the head must in such cases of course take place 
 inside the bladder, from which even the perfectly formed heads may 
 be seen for a while projecting, with the hooks and suckers directly 
 outwards. When these are subsequently drawn back to the cervical 
 region, the heads, which have originated in this way, look like the 
 others. 
 
 If we suppose that the brood-capsules represent a pushing in of 
 the Echinococcus-wall, as is diagrammatically represented in Fig. 205, 
 then the difference between the Echinococci and the ordinary bladder- 
 worms, and particularly the Ccenurus, is essentially limited to this 
 point, that the heads are budded off from these invaginations, instead 
 of from the proper bladder-wall. This supposition does not as a 
 matter of fact seem so incorrect or unreasonable, although the brood- 
 capsules arise, as we shall afterwards see, without any participation on 
 the part of the cuticle. At any rate we can thus very simply express 
 the essential peculiarities of the Echinococci, and their relation to the 
 other bladder-worms. 
 
 As to the fact that the cuticle takes no part in the formation of 
 the brood-capsule, this may perhaps find some explanation in the very 
 unusual thickness which we found it to possess in the Echinococci. 
 There are some whose cuticle is a millimetre thick, and, besides 
 such instances which occur in the larger forms, even the smaller 
 
 G ' 
 
 Echinococci are provided with a very thick cuticle ; and not only is 
 it very thick, but it also shows a characteristic lamination, which 
 particularly demands our attention, since it not unfrequently happens 
 that new Echinococcus-bl&dders are found between the layers, whence 
 they burst forth either outwards or inwards, often at an early stage, 
 and become independent bladders. 1 
 
 According to the precise nature of this proliferation, various forms 
 of Echinococcus have been distinguished, as we shall afterwards see, 
 when we come to discuss in detail this interesting bladder-worm. 
 
 As a rule, daughter-bladders and brood-capsules are only formed 
 at a later stage, when the bladder proper has attained a considerable 
 size. Sometimes they seem never to occur. We know at least of 
 numerous cases in which the Echinococci produce no daughter-bladders, 
 in which we look in vain for brood-capsules or heads, and yet we are 
 not warranted in distinguishing these though it has been done as 
 distinct species. 
 
 1 I may take this opportunity of mentioning that I have to thank Dr. A. Schmid, in 
 Frankfort on the Main, for a Cysticercus tenuicoUis, whose bladder encloses a few isolated 
 daughter- bladders. 
 
THE CONNECTIVE-TISSUE CAPSULE. 359 
 
 Where the bladder-worm lies in parenchymatous organs rich in 
 connective tissue, it never leaves its cuticle exposed. It is constantly 
 found enclosed in a connective-tissue envelope, which belongs not of 
 course to the worm, but to the host and the organ inhabited. The 
 inner surface of the capsule is smooth, like a serous membrane, and 
 is furnished with a cellular layer, which is possibly of importance in 
 the excretion of the nutritive fluid. We cannot, however, regard the 
 cyst as essential to the nourishment of the animal, since it is wanting 
 in many situations e.g., in the eye and in the brain. The surface of 
 the Coenurus-c&vity (in the brain of the sheep afflicted with staggers) 
 is covered with a tough layer, which is sometimes separable in large 
 shreds, but does not exhibit in any way the ordinary structure of the 
 bladder-worm cyst. One can indeed see in it the remains of nervous 
 substance and vessels in all stages of disintegration and degeneration, 
 a striking proof of the disastrous effect of parasites. 
 
 The connective-tissue cyst of the adult bladder- worm is by no means 
 always identical with that which surrounds the young parasites after 
 their immigration. It only persists when the worm remains in its 
 first resting-place. But occasionally the worm retains for some time 
 the power of changing its abode, especially if the organ in which it 
 has landed is poor in connective substance. In spite of their increased 
 size, the young immigrants press slowly forwards, probably by con- 
 tinuous peristalsis, and press the surrounding tissue to the side. Thus 
 one finds young Ocenuri on the surface of the brain, forming passages 
 an inch long, lined with long shreds of exuded matter. Similarly 
 
 FIG. 206. Brain of a lamb with passages of Coenurus (natural size). 
 
 the Cysticerci of the liver and lungs press ever outwards, and often 
 break through into the body-cavity. There are even species which reach 
 the body-cavity in this way only. To these belongs, for instance, the 
 Cysticercus pisiformis, so common in our hares and rabbits. Three 
 or four weeks after an infection with Tcenia serrata, the liver of 
 these animals is seen to be perforated often by countless white 
 streaks the borings of the young Cysticerci which almost all 
 gradually lead to the surface, and allow their inmates to get out. 
 
360 
 
 THE DEVELOPMENT OF CESTODES. 
 
 FIG. 207. A piece of rabbit's liver with 
 passages of Cysticercus pisiformis. ( x 10.) 
 
 The worms then remain for a while free in the body-cavity, but after 
 some weeks one finds them once more in a cyst hanging usually to 
 the omentum or the connective-tissue covering of the intestines. The 
 
 Cysticerciis tenuicollis of our rumi- 
 nants behaves in an exactly 
 similar way, as we shall after- 
 wards notice in greater detail. 
 
 According to the observa- 
 tions on which we rely, the de- 
 velopment of the cystic worms 
 always begins with the formation 
 of the subsequent bladder. As 
 to the origin of the latter, we 
 have no direct results, but we 
 can hardly be mistaken in regarding it as the enlarged and 
 modified embryonic body. 1 This supposition becomes a certainty 
 when we examine the more microscopic so-called " Cysticercoids," 
 which resemble the above-described bladder-worms in all essentials, 
 and differ only in their minuteness and in the absence of fluid. 
 
 These parasites are found ex- 
 clusively in cold-blooded animals, 
 especially among invertebrates, 
 such as insects and molluscs. As 
 yet but few forms are known not 
 more than a dozen although we 
 have reason to believe that they 
 far exceed the bladder -worms 
 proper in the number of their 
 species. 
 
 In one of these forms, to 
 which we have already (p. 331) 
 referred the Cysticerciis tene- 
 brionis, which is probably the 
 
 Fw. 208. Development of Cysticercus m . ..{.*. 
 
 tenebrwnis (after Stein). A, Embryo after young stage of a Tcema inhabiting 
 
 the hooks are cast off ; , Adult Cysticercus. the mouse Stein has described 
 
 (x about 100.) , , . A , 
 
 the gradual passage of the em- 
 bryonic body into the subsequent bladder. The six-hooked embryo 
 
 1 I believe that I once found the six embryonic booklets near the anterior end of the 
 body of a young Cysticercus pisiformis (" Blasenbandwurmer," p. 120). Professor Ed. van 
 Beneden has, he tells me, been more fortunate, having repeatedly demonstrated these hooks 
 on bladder-worms of Ttenia saginata 0'4 to 0'5 mm. in size. Three times all the six hooks 
 were present in varying position, while in other cases we could see only a few, or only one. 
 [Raum also (loc. cit. supra) appears to have several times found the embryonic hooks in 
 young specimens of Cysticercus pisiformis, whose heads were still undeveloped. R. L.] 
 
OCCURRENCE OF THE EMBRYONIC HOOKS IN BLADDER -WORMS. 361 
 
 becomes surrounded by a cellular layer which belongs to the 
 host, and grows out posteriorly into a lappet. The hooks are then 
 cast off, but may be observed for a while in the cellular layer, and 
 the tape-worm head is developed within the embryo. These reports 
 of Stein are unfortunately so far uncertain, that von Siebold thought 
 himself justified in regarding the tail-like posterior appendage as an 
 integral part of the worm. This seems all the more plausible, since 
 it is on it that embryonic hooks are always found. 1 
 
 So much the more grateful is it that we know other Cysticercoids 
 which enable us to decide as to the relation of the six-hooked 
 embryo to the bladder- worm. 
 
 Among these first and foremost is the so-called Cysticercus arionis, 
 which is not unfrequently found in great numbers 2 in the pulmonary 
 cavity of the red slug, and which originates from the Tcenia of a bird, 
 probably a red-shank (Totanus calidris). Meissner found here all 
 the six hooks in their proper arrangement, but he so far misunderstood 
 their position and the structure of the worm, that he overlooked the 
 caudal bladder, and regarded the hooks which occurred at the passage 
 of the latter into the neck as if they were at the posterior end. Such 
 appearances as Meissner saw and figured are not unfrequently seen, 
 but only when the body has been separated by pressure from the 
 caudal bladder, which is all the easier since the cuticular covering of 
 the latter possesses an unusual thickness and firmness, and is besides 
 histologically very different from the former. If, after removing the 
 surrounding connective-tissue cyst, one treat the worm for a short 
 time with lukewarm water, the head can be seen stretched out, and 
 the existence of an actual caudal bladder (Fig. 209, B) is placed 
 beyond doubt. The latter exhibits under its cuticle a cellular layer, 
 whose elements are of considerable size, and enclose a dull granular 
 mass penetrated by fat globules, while the parenchyma of the tape- 
 worm body seems to consist mainly of small clear cells, between 
 which numerous muscle-fibres and calcareous bodies are embedded. 
 
 In its quiescent state, the body of the tape-worm is wholly retracted 
 within the caudal bladder, so that the outer boundary is formed exclu- 
 sively from the thick cuticle above mentioned (Fig. 209, A). The 
 
 1 Moniez has indeed convinced himself ("Essai monogr. Cyst.," loc. cit., p. 78) that 
 the caudal appendage and the cyst of Stein belong to the Cysticercus, and therefore that 
 the latter, essentially like a young Cysticercus pisiformis, lies naked in the body-cavity of 
 the host. 
 
 2 In one case I counted over a hundred Cysticerci side by side on the wall of the 
 pulmonary cavity. See as to this worm especially my work on "Blasenbandw tinner," 
 p. 115, where its structure is for the first time rightly described. The objections which 
 Moniez has lately made (loc. cit., p. 73) to my description apply only to matters of subor- 
 dinate importance, and cannot all be regarded as settled points. 
 
362 
 
 THE DEVELOPMENT OF CESTODES. 
 
 point of connection is seen as a narrow mouth-like opening, near 
 which, in successful preparations, the embryonic hooks may be clearly 
 seen. Since this is just the position at which the rudiment of the 
 head first appears, one might suppose that the latter is formed also in 
 the bladder- worms proper from the anterior hook -bearing segment of 
 the embryo. 
 
 Fio. 209. Cysticercu* arionis with head retracted (A), and protruded (). ( x 50.) 
 
 The formation of the head has not, however, as yet been directly 
 observed in Cysticercus arionis. This is the more to be regretted since the 
 adult head is by no means a mere repetition of the ordinary Cysticercus 
 type, but has its anterior end (with rostellum and hooks) always 
 turned towards the place where the bladder was invaginated. It 
 bears its suckers exposed on its outer surface. In position and atti- 
 tude it thus resembles what we have occasionally seen, though only 
 exceptionally, in the older bladder-worms (Fig. 201). Like the head 
 of the future tape- worm, that of Cysticercus arionis seems to be a solid 
 body, which fills up by far the greater portion of the caudal bladder, 
 with which it is not, however, connected directly, but only by means 
 of a cylindrical or sac-like connecting part the future neck. 
 
 From the analogy of the Cysticerci just referred to, I think we may 
 conclude that the head of Cysticercus arionis does not from the first appear 
 in this attitude, but that it only assumes it in consequence of a change 
 in the disposition of its parts. Here also I believe the development of 
 the future tape-worm begins with the formation of a hollow bud, 
 which starts from the wall of the enlarged embryonic body and grows 
 into the loose interstitial tissue of the same. This does not become 
 the sac-like and invaginated future neck portion in which the head is 
 
DEVELOPMENT AND POSITION OF THE HEAD. 363 
 
 only subsequently to originate; it begins from the first, as in the 
 genuine forms, to become the head. 1 When the neck is formed the 
 elevation begins to take place ; the lower end of the sac, which has 
 become the head, is pushed in like a plug into the other portion. 
 
 This pushing in of the head is a constant characteristic of these 
 bladder-worms, and is not merely occasional, as may be established 
 from a consideration of some features in the organization. In the 
 Cysticercusfasciolaris of the mouse, in which the same mode of formation 
 was observed, we referred the protrusion of the head to the consider- 
 able elongation of the connecting part ; in Cysticercus arionis it is pro- 
 bably the elongated proboscis-like portion which bears the hooks that 
 determines the protrusion. This supposition is confirmed by the fact 
 that in all the other Cysticercoids with an elongated proboscis the 
 same position and attitude of the head are found to obtain. Thus I 
 find it, for example, in a Cysticercoid from the liver of Lymnceus pereger, 
 which closely resembles the Cysticercus arionis in its whole organization, 
 and which, from the structure of its hooks, may probably be referred 
 to the Tcenia microsoma of the wild duck. So is it also with the 
 Cysticercus of Tcenia gracilis 2 found by v. Linstow among the remains 
 of small crustaceans in the intestine of a young perch, and in the 
 Cysticercus lumbriculi found by Eatzel in Scenuris variegata* which 
 probably becomes T. crassirostris in the intestine 
 of the snipe and other water-birds. The Cysticer- 
 coid forms of the Tcenice of the shrew (T. pistillum 
 and T. scutigera T) lately described by Villot from 
 Grlomeris, 4 * are also closely connected with Cysti- 
 cercus arionis in the nature both of its head and of 
 its rostellum. 
 
 There are, on the other hand, also Cysticercoids 
 in which the rudiment of the head originates and FIG. 210. Cysti- 
 grows in the typical bladder-worm fashion which 
 we have formerly described. There are, as we 
 should expect, forms with short rostellum, such as Nordmann's Gypo- 
 
 1 Stein is the only investigator who has observed the first developmental stages of a 
 Cysticercoid. Speaking of this process he says "The further changes of the encysted 
 embryo are as follows : an ever-deepening depression is formed at the truncated anterior 
 end, and the head, with its proboscis and suckers, is at the same time formed in the 
 centre of the embryonic body from the absorbed ground-substance, "Zoc. cit.,p. 210. The 
 accompanying figures show in Tab. x., Fig. 13, a Cysticercus with invaginated portion 
 and rudiment of head, whose hooks are hardly raised as far as the middle of the bladder 
 body, while they are afterwards found close behind the point of invagination. 
 
 2 Archivf. mikrosk. Anat., Bd. xxi., p. 535, 1871. 
 
 3 Archivf. Naturyesch., Jahrg. xxxiv., Bd. i, p. 147, 1868. 
 
 4 "Migrations et metamorphoses des Te"nias des Musaraignes," Ann. Set. nat., ser. 
 6, t. viii., Art. 5, 1878 ; also Ann. Mag. Nat. Hist., ser. 5, vol. i., p. 258. 
 
364 THE DEVELOPMENT OF CESTODES. 
 
 rhynchus, with which we have become more intimately acquainted 
 through Aubert, 1 and also the young form of the Tcenia cucumerina 
 of the dog. 
 
 Two closely related species of the former live in the tench the 
 one between the intestinal villi, the other in the gall-bladder ; in 
 situations, therefore, which are only rarely inhabited by young Hel- 
 minths. They exhibit, also, a habit very unusual for a bladder- 
 worm, namely, that of occasionally stretching the head out of the 
 caudal bladder and creeping about inside their place of abode, like an 
 adult tape- worm. Even in this state, however, the adherent caudal 
 bladder, which is sharply separated from the rest of the body both 
 externally and histologically, attests undeniably their Cysticercoid 
 nature. To reach their adult state, they have to pass into the in- 
 testine of the heron, where, according to Krabbe, they are to be 
 recognised by the characteristic structure of the hooks, as Tcenia 
 macropeos and T. unilateralis. As to the position of the head in 
 the invaginated state there can be no doubt, after Aubert's description 
 and figures. 2 "The points of the hooks are," he says, "turned to- 
 wards the posterior end of the animal, while the central fixed portions 
 lie towards the unfolding of the fat-sac (i.e., towards the point of 
 invagination of the caudal bladder), and towards the same point be- 
 tween it and the circle of hooks lie the suckers." All this agrees 
 exactly both with the formation of a typical Cystieercus and with the 
 state of affairs in the Cysticercoid of Tcenia ellip- 
 tica (=T. ciwumerina), which, as is well known, 
 undergoes its development in the body-cavity 
 of the dog-louse (Trichodectes canis) (Fig. 211). 
 
 The latter may be ranked by the side of 
 Gyporhynchus, on the ground of the morpho- 
 logical similarity between the two. Both arise 
 in similar fashion from a sac, and from a Tcenia- 
 head invaginated therein. The resemblance, 
 however, stops here ; for, in their further rela- 
 tions, the two forms differ widely. This is the 
 Fro. 211. Cysticercoid of ca se at least with the external body, which we 
 I(x60) 'have just called the "sac." In the Gypo- 
 rhynchus this exhibits a distinct caudal bladder, as in the other Cysti- 
 cercoids which we have discussed. This bladder is in form and 
 histology sharply distinguishable from the rest of the body, and re- 
 tains its independent character even in the outstretched state. In 
 the Cystieercus of Tcenia elliptica, however, the bladder seems in 
 
 1 Zeitschr.f. wiss. Zool., Bd. viii., p. 274, 1857. 
 
 2 Loc. cit., p. 285, Tab. x., Fig. 7. 
 
POSSIBLE ABSENCE OF THE CYSTICERCOID STAGE. 365 
 
 appearance and character simply as a process from the head-bearing 
 anterior end, belonging to it much in the same way as the neck 
 portion of an Echinococcus to its head. Here we find in an exaggerated 
 degree the same structure as we formerly noted in regard to the 
 " parenchymatous Cysticerci." 
 
 It seems doubtful whether we can refuse to recognise at least the 
 genetic identity of the sac-like external body of this Cysticercus with 
 a caudal bladder, especially since the results of the discoverer's x inves- 
 tigations, which were controlled and corroborated by myself, make it 
 probable that the subsequent external body is formed directly from 
 the six-hooked embryo. The details of the development are unfor- 
 tunately unknown; we only know that the immigrant embryos, 
 before the loss of their hooks, grow to about half the size of the 
 Cysticercoid, and change their original shape for a somewhat 
 pear-like form. The embryonic hooks are not to be found on the 
 adult Cysticercoid. 
 
 We must, moreover, admit the possibility of the young tape-worm 
 being developed by a simpler process than through the Cysticercoid 
 form. I am led to this admission partly by a communication of Dr. 
 Gruber's in regard to a young Tcenia, which he has since described 
 elsewhere, and which he found in investigating the littoral fauna of 
 the Boden See. 2 It was a worm about a millimetre long, which was 
 found stretched out in the body-cavity of Cyclops serrulatus, occupying 
 almost the whole space above the alimentary canal between eye and 
 abdomen. Special parts could hardly be distinguished; the body 
 consisted of a clear mass, with uniformly diffused calcareous bodies ; it 
 had a simple cylindrical form, and was furnished at the somewhat 
 
 FIG. 212. Young form of Tasnia torulosa (?) in Cyclops serrulatus. after 
 Gruber. ( x 25.) 
 
 thickened, hookless, anterior end with four distinct suckers. In the 
 great multitude of infected Cyclops, it was difficult to find the previous 
 stages. None of these, however, had the form of a Cysticercus. They 
 
 1 Melnikoff, " Ueber die Jugendzustande der Taenia cucumerina," Archivf. Naturgeach., 
 Jahrg. xxxv., Bd. i., p. 69, 1869. 
 
 3 Zool. Anzeiger, Jahrg. i., p. 74, 1878. 
 
366 THE DEVELOPMENT OF CESTODES. 
 
 \vere all simple, round, or pear-shaped bodies, some of very minute 
 size, which seem to pass directly by growth and formation of suckers 
 into the definite larval form. Their origin is uncertain, though Gruber 
 suggests their connection with the hookless Tcenia torulosa of our 
 white fish. This is corroborated by the fact that I once found a 
 number of young Tcenice in the intestine of a loach, which perfectly 
 agreed in size and appearance with the forms described by Gruber, 
 and in addition to the calcareous corpuscles also exhibited four coiled 
 vessels running down the body. 
 
 The demonstration of the nature and history of the ordinary Cysti- 
 cercoid condition does not, therefore, complete our knowledge of the 
 development of the Tcenice, as is further evidenced by the observations 
 made by Mecznikoff in Odessa on a parasitic " Uchinococcus-likQ" 
 larval stage of an otherwise unknown twelve-hooked Tcenia. 1 This 
 Echinococcus-likQ form was found in the body-cavity of the common 
 earth-worm. . In its mature condition it consists of a thin-skinned 
 bladder (Fig. 213, E\ which contains a varying number (up to 
 thirteen) of small Cysticerci of about 0*5 mm. in diameter. 
 
 FIG. 213. Development of an Echinococrus-llke Cysticercoid from the 
 body-cavity of the earth-worm, after Mecznikoff. ( x 25.) 
 
 Although the latter lie quite free in the interior, and possess, 
 like the ordinary Cysticercoids, the distinctive caudal bladder, they 
 are of very unusual origin, inasmuch as, instead of developing directly 
 from the six-hooked embryos, they arise by proliferation of the wall 
 of the surrounding bladder (Fig. 213, B). The bladder is thus the 
 brood-capsule of the enclosed Cysticercoids, and corresponds in some 
 respects to the brood-capsule of the Echinococcus, or perhaps to a 
 
 1 Verhandlungen d. Petersburger Naturf. Versamml., Zool, pp. 263-266, 1868 (in 
 Russian). The worms were given to ducks, but without result. According to the 
 structure of their hooks they close resemble, if they be not identical with, Tcenia nilotica, 
 Krabbe, from the intestine of Cursor isabcttinus. 
 
COLONIAL CYSTICERCOIDS. 367 
 
 CW^rws-bladder, and, like these, is undoubtedly to be referred to 
 the six-hooked embryo. The first developmental stage observed by 
 Mecznikoff appeared to be a solid ball of about O08 mm., with an 
 unusually thick cuticular envelope and cellular contents. The latter 
 subsequently become clear on attaining a diameter of 0*14 mm., when 
 the embryo lies upon the inner surface in the form of a cellular layer. 
 Soon the buds begin to form, and that exclusively from the cellular wall, 
 which becomes thicker at certain spots, and sends little projections (A) 
 into the inner cavity. Although at first flat, and connected by their 
 broad bases with the cellular wall, the protuberances, as they grow 
 larger, gradually detach themselves from the subjacent layer. This 
 separation is facilitated by the development of a hollow space in the 
 interior of the basal portion, 1 so that after a time the bud is only con- 
 nected with the mother-bladder by a thin filament (B). Finally, this 
 connection is destroyed, and the bud thus becomes an oval body lying 
 freely in the interior. It then proceeds to undergo its further develop- 
 ment. This is essentially the same as that which we have already 
 served in the buds situated inside the brood-capsule in the Echino- 
 cocci, only that in this case not only head and neck are formed, but a 
 third joint, consisting of a kind of caudal bladder. All these parts 
 are formed almost simultaneously, for the originally compressed and 
 solid bud increases in length, then becomes hollow inside, and 
 becomes jointed by the development of the hook-apparatus in front 
 and a bladder-like expansion behind. When the suckers and hooks 2 
 are completely developed (Z>), the anterior part of the body draws 
 back into the caudal bladder by invagination of the neck, so that at 
 the end of its development the worm has exactly the same position 
 as we formerly observed in Cysticercus arionis. 
 
 The short description which we have given of this wonderful 
 Tcenia form by no means exhausts the similarities which sometimes 
 exist between the Cystercoids and the Ecliinococci. The former are 
 not only capable of internal proliferation, but in some cases multiply 
 also by external buds. 
 
 Villot observed this process in the already mentioned Cysticercoids 
 of Glomeris, where it was so often repeated, that the parasites assumed 
 quite a racemose appearance, from which fact, indeed, he has named 
 these forms " Staphylocysts." In this form they may be seen hanging 
 together in dozens (Fig. 214, A) in the ureter of their host. Such a 
 colony contains larger and smaller, younger and older bladder-worms, 
 
 1 Mecznikoff inaptly compares this hollow space to the interior of a brood-capsule. 
 
 2 Although the rudimentary hooks are in a double row, the definitive hook -apparatus 
 consists only of a single circle, for the rudiments of the second circle become abortive, and 
 disappear. 
 
368 
 
 THE DEVELOPMENT OF CESTODES. 
 
 at different stages of development, and all hanging together by means 
 of a thin stalk at the posterior end of the caudal bladder. Here, too, 
 of course occurs the formation of the buds, which at first are nothing 
 else than accumulations of cells, which force their way out, and are 
 surrounded by a continuation of the cuticle. It is unnecessary to 
 give any account of the metamorphosis of the buds, since to do so 
 would only be to repeat what we have already noted in the case of 
 Cysticcrcus arionis regarding the structure of the tape-worm head and 
 of the later caudal bladder ; for in this case the bud is nothing else 
 than a repetition of the six-hooked embryonic body. 
 
 FIG. 214. Cysticercvt glomeridis (after Villot). A, Two groups of bladder-worms 
 produced by proliferation (under low power) ; , Cytticercu* in its natural position ; 
 and (7, with evaginated body. ( x 200.) 
 
 After these observations, it cannot be doubted that the develop- 
 ment of the Tcenice follows, on the whole, the same type in the higher 
 and lower forms. With the exception of a few somewhat doubtful 
 cases, this is true throughout of the Cysticercoid state. It is true 
 that many differences occur in the size and nature of the bladder ; but 
 however remote certain species may be from each other, they are 
 always connected by intermediate forms. Consequently, the difference 
 which we formerly established between the true bladder-worms and 
 the Cysticercoids becomes a distinction of somewhat doubtful value. 
 
 On the other hand, it must not be overlooked that the apparently 
 " dropsical " nature of the bladder in the genuine bladder- worms con- 
 stitutes a very remarkable and striking peculiarity, and all the more 
 
PHYSIOLOGICAL SIGNIFICANCE OF THE CYST. 369 
 
 striking since we can give no plausible explanation of it. It might 
 certainly be supposed that the watery contents of the bladder formed 
 a nutritive fluid, if this idea were not excluded by the extremely 
 small quantity of nutritive material which it contains (0'2 to 0'3 per 
 cent, of albuminoids, 1 and 0'03 to 0*05 of fat). Neither does the 
 chemical analysis of the water of the bladder show it to be an ex- 
 cretory product ; for it yields, apart from the above substances, a weak 
 saline solution (with about 3 per cent, of salts, mostly of soda). 
 
 Under these circumstances, there is hardly any alternative but to 
 regard the collection of water as an arrangement for securing certain 
 individual advantages. Perhaps in this way a more favourable, that 
 is to say an increased, absorptive surface is furnished to the parasite, 
 or perhaps greater protective needs are thus met. A fact possibly 
 of importance in this last respect is that the genuine bladder- worms 
 are apparently exclusively confined to the Mammalia, so that some 
 protective arrangement is therefore very necessary to them, on 
 account of the size and motions of their hosts. The theory that the 
 effects secured by the apparent dropsy are of a mechanical nature, 
 seems the more plausible since similar arrangements have occasionally 
 been observed to fulfil similar functions in the Graffian follicles, in 
 the amnion, and in the eye. 
 
 But when we use the term "bladder -worm" in a wider sense 
 than the older Helminthologists did, we note at once that the presence 
 of this developmental phase is by no means limited to the Tcenice, but 
 occurs on the whole almost universally among the Cestodes. One has 
 only to cast a glance over the often-quoted treatises of van Beneden 
 and Wagener to notice large numbers of such forms in the most 
 diverse families of tape-worms. Even Eudolphi observed this struc- 
 ture in a few of these bladder- worms. The forms which he mentions 
 belong exclusively to the marine group of the Tetrarhynchi, and, from 
 their size and occurrence in the muscles and in the parenchymatous 
 viscera (in fishes), must be allied to the genuine Cysticerci. These 
 worms could not of course be ranked with the genus Cysticercus, for 
 the form of their heads was quite different (" caput bothriis 2 vel 4 et 
 proboscidibus uncinatis 4 instructum"). They were therefore regarded 
 as the representatives of a distinct genus, Anthocephalus, which, by 
 the structure and armature of its head, recalled certain Bothriocephali 
 living in the intestines of rays and sharks (now called Tetrarhynchi, 
 Eudolphi's RliyncJiobothrii), just as the other bladder-worms recall 
 the Tcenice. 2 
 
 1 It is on account of this small qxiantity of albumen that the bladder-fluid can be 
 coagulated neither by boiling nor by the addition of acids. 
 
 3 Nitzsch in Ersch and Gruber's " Encyclop.," Art. Anthocephalus, Bd. iv., p. 259, 1820. 
 
 2 A 
 
370 
 
 THE DEVELOPMENT OF CESTODES. 
 
 FIG. 215. Cysticercoid Tetrarhyn- 
 chus from a Mediterranean Percoid. 
 A, in its natural position ; Jt, with 
 evaginated body. ( x about 20.) 
 
 On the other hand, it is true that the Cysticercoid nature of the 
 Anthocephali has been doubted. My uncle F. S. Leuckart explained 
 
 the latter, in opposition to Rudolphi, as 
 young Tetrarhynchi (or Bothriocephali), 
 and denied the interpretation of the 
 surrounding bladder as a caudal bladder, 
 since even in examples sent by Kudolphi 
 (A. gracilis) both Bremser and he 
 found the posterior end of the tape- 
 worm free and without any connection 
 with the surrounding bladder, and 
 could not perceive any rupture in it. 1 
 We now know that both investigators 
 were right. 2 
 
 In spite of their considerable size, the AnthocepJiali belong, how- 
 ever, to the parenchymatous bladder-worms. Instead of water, they 
 contain (see Fig. 219) an areolar connective tissue, which fills 
 the whole of the interior, and is in continuous connection with the 
 external envelope of the body. 3 This circumstance also explains 
 how the Anthocephali, and especially the larger ones, instead of 
 developing into balls, stretch out longitudinally, and sometimes 
 assume an almost tape-worm-like form. This is most striking in the 
 species (Anthocephalus s. Gymnorkynchiw reptans) living in the 
 muscles of Brama Raji, which in course of time becomes a ribbon 
 almost a yard long, and only exhibits a ball-like swelling near the 
 anterior end where the receptaculum with the head is placed. 
 
 The appearance of ttye head after development is always the same 
 as in the adult tape-worm. It forms a solid mass with outwardly 
 directed suctorial pits, and, as in the majority of the Cysticercoids, 
 is raised like a plug from the floor of the receptacle with which 
 it is at first always in continuous connection (Fig. 215). In many 
 species this connection is permanent, so that the receptacle distinctly 
 appears as an integral portion of the tape-worm, like the evaginated 
 neck, which, in the other Cysticercoids, is generally the means of con- 
 nection with the caudal bladder. In other species, however, the 
 former connection is dissolved when the head is perfectly developed, 
 and then the latter lies quite free in the interior of the former neck, 
 as my uncle quite correctly observed within the first twenty years of 
 
 1 Zoologische JBruchstiicke, Heft i., p. 67, 1819. 
 
 a See in regard to this v. Siebold's " Abhandlung iiber den Generationswechsel der 
 Cestoden," Zeitschr. f. wis*. Zool., Bd. ii., p. 200, 1850, and van Beneden, Mtm., &c., 
 p. 76. 
 
 8 Hoek, "Ueber den encystirten Scolex von Tetrarhynchus, " Niedcrldnd. Archiv f. 
 Naturwiss. 1879. 
 
WANDERING OF THE HEADS OF TETRARHYNCHUS. 371 
 
 this century. In such cases the free posterior end has usually a thick 
 fringe of hair-like spines, just as in the Tetrarhynchi the rest of the body 
 is frequently covered to a large extent with small closely set bristles. 
 Not unfrequently this separation of the head leads in course of 
 time to a complete emigration. Not only are Tetrarhynchus-bladders 
 frequently found forsaken by their inmates, but also Tetrarhynchus- 
 heads occur in places and in animals in which the other stages of 
 their development are sought for in vain. Of the numerous cases of 
 this kind (all those forms which Eudolphi originally enumerated in 
 his genus Tetrarhynchus consist simply of these isolated heads) I shall 
 only mention 1 the Tetrarhynchus-heads found in the muscles of Sepia 
 (T. macrobothrius ? Fig. 216), which sufficiently reveal their origin 
 by the hair-like fringe at the posterior end, and have already been 
 frequently observed by former investigators (Eudolphi, delle Chiaje, 
 Wagener, &c.). At one time they are found boring and digging 
 between the fibrous bundles of the mantle, and at another time quies- 
 cent, and then surrounded by a thin envelope of connective 
 tissue, but always at the same stage of development. 
 Only in size do they exhibit any marked difference, for 
 some have double the diameter of others, but this 
 amounts to nothing more than that these inmates have 
 remained in their host for a different length of time. 
 The latter are not, of course, to be regarded as the final 
 hosts. They play the part of intermediate hosts, and 
 only affect the life-history of our parasite, in so far as m FlG - 216. 
 
 . J 1 . _. ., . J Tetrarhynchus 
 
 they extend its distribution and facilitate or render pos- sepia ( x 12). 
 sible the subsequent transference. 
 
 It also looks as though the Tetrarhynchi furnished by no means the 
 only example of such a change of hosts. 
 
 Young unjointed Cestodes, not unlike isolated heads of Tcenice, 
 have long been known to inhabit the intestines of many sea-fish. 
 These have a so-called " frontal sucker," more or less highly developed 
 between the other four suctorial pits, and not unfrequently also two 
 red eye-spots behind the hook apparatus. Eudolphi founded a special 
 genus (Scolex) for these animals, and thought that they ought all to 
 be regarded as representatives of a single species (S. polymorphus). 
 
 Thanks to the investigations of Wagener and van Beneden, we 
 have, however, become more thoroughly acquainted with these para- 
 sites. We now understand not only how to distinguish the different 
 species, but also know that these gradually change the originally 
 simple structure of their suctorial cavities for a more complicated 
 
 1 According to a communication of v. Ihering, the genus Tethys may be added to the 
 number of the animals in which these parasites are known to occur. 
 
372 
 
 THE DEVELOPMENT OF CESTODES. 
 
 . 
 
 FIG. 217. Scdece* : A from the intestine of 
 Sepia (after van Beneden) ; B from Lophius 
 
 (x about 30.) 
 
 one, and ultimately become forms, which were formerly like the Tetra- 
 rhynchi, ranked among the Bothriocephali, but since the time of 
 
 van Beneden have been more 
 correctly described as Phyllo- 
 lothria (in the widest sense of 
 the word). The adult worms 
 live, like the Tetrarhynchi, 
 principally in rays and sharks. 
 Thus I think I am now 
 entitled to regard these Scoleccs 
 as structures parallel with 
 the wandering Tetrarhynchus- 
 heads ; and this all the more 
 decidedly since they not only 
 live in a wandering state in 
 
 ,.~. i /i ., 
 
 y ery different animals (besides 
 
 fishes, in Cephalopoda, snails, and 
 Ctenophora), but are also frequently observed swimming about in a free 
 state. 1 In the frequent possession of eye-spots, we might even see an 
 arrangement which specially adapts these animals for active wandering. 
 
 The parallel would be perfect if we could show that these Scoleces 
 originated, like the Tetrarhynchus-hends, in the interior of a bladder. 
 
 And indeed it cannot be doubted, after the observations of van 
 Beneden, that there are Phyllobothria, which pass through a Cysticer- 
 coid larval state (Phyllobothrium lactuca and Acanthobothrium coro- 
 natum)* But it appears as if these observations referred only to 
 such Cestodes as retain their early state until they are transferred 
 to their final host. At any rate the forms observed by van Beneden 
 exhibit even as bladder-worms in the appearance of their suckers a 
 very close approximation to the subsequent state. A similar structure 
 is found in a Cysticercoid of a Phyllobothrium (Echeneibothrium T) 
 which Wagener found in the large intestine of a Trygon. " Like a 
 Tetrarhynchus, the animal was suspended by threads in a sac within 
 its caudal bladder. Its head had hairs and its neck red spots. The 
 bladder was burst by pressure and the animal was set free. There 
 
 1 Claparede twice fished a Scoltx of this sort out of the sea, and quite correctly con- 
 cluded that a "normal migration" occurred, (" Beobacht. iiber Anatomie u. Entwicke- 
 lungsgesch. wirbellose Thiere," p. 14, 1863.) The animals possessed four suckers with 
 double cups (Bothria bilocularia), and swam by a snake-like motion of the whole body. 
 Panceri found a similar Scoltx on the skin of Brama Raji (" Rendiconto Accad. Napoli, 
 February 1868). 
 
 a With this ought to be ranked Rudolphi's Cysticercus ddphini, which was till lately 
 referred to the Cysticerci proper ; see P. J. van Beneden, Bullet, acad. roy, elg., t. xxix., 
 p. 360, 1870. 
 
MORPHOLOGY OF RUDOLPHl'S SCOLEX. 373 
 
 were no joints to be seen. Its lower end was still firmly attached by 
 a thread to the caudal bladder which collapsed." * The description 
 indeed suggests that the head was in this case destined to be set free, 
 and to wander on its own account, but from the complicated form 
 of its suckers it could hardly be regarded as a Scolex in Eudolphi's 
 sense of the term. 
 
 Under these circumstances, then, there is little support for the sup- 
 position that the Scoleces, with which we formerly became acquainted, 
 are to be interpreted as the isolated heads of a Cysticercoid develop- 
 mental stage. It is, of course, conceivable that such a relation may be 
 afterwards proved, but we ought to bear in mind the possibility 
 that, unlike what is the case in Tcenia cucumerina, the apparent heads 
 may be regarded as Cysticercoid forms with appended, although not 
 histologically differentiated, caudal bladders. 
 
 This is a view which essentially coincides with the idea which we 
 find, though unformulated, in Wagener's excellent treatise on the 
 development of the Cestodes. 2 What led him to it was at first only 
 the presence of a " pulsating tube " opening at the posterior end of the 
 body. This organ he regards as a characteristic peculiarity of the 
 caudal or Cestode bladder (" the head -former "), which springs from 
 the hooked embryo, and he further proves the existence of this de- 
 velopmental stage in numerous cases, and always in connection with 
 a more or less complicated and often ciliated vascular apparatus. Of 
 no less significance is the fact that Wagener frequently found the 
 Scoleces " with heads drawn back " (compare the illustrations in Tab. 
 ix. of his work), that is to say, in a position which so perfectly corre- 
 sponds with the already mentioned Cysticercus Tcenice cucumerince, that 
 one cannot refrain from collating the two forms. It is certainly strik- 
 ing and unusual in a Cysticercoid form for the Scoleces to live free 
 and mobile in the intestine of their host, but in Gyporhynchus, also 
 found in fish, we find this in an unmistakeable Cysticercoid. 
 
 If our idea be correct, then there are Cysticercoid forms among the 
 Phyllobothria as well as among the Tcenice, whose caudal bladder is 
 both anatomically and histologically an integral portion of the head, 
 being developed inside it, and being sometimes subsequently drawn 
 back into it. 
 
 In this retracted state the head of the Scolex is in exactly the 
 same position which we formerly found that organ occupying in 
 the Cysticercus of the dog-louse, and which we then considered as 
 mainly characteristic of the bladder-worms. The drawings which 
 
 1 Loc. cit., p. 58. 
 
 2 Van Beneden also directly mentions the above-mentioned Cysticercus of Phyttoboth- 
 riwn lactuca and Acanthobothrium as a Scolex (loc. cit. pp. 73, 74). 
 
374 THE DEVELOPMENT OF CESTODES. 
 
 Wagener has made of it (see especially Fig. Ill of his work) leave 
 not the slightest doubt on this point. According to the description 
 
 of van Beneden, a similar appearance is 
 found in the Cystieercus of Acanthobothrium 
 coronatum. The cavity of the suctorial 
 cups is always directed towards the interior 
 of the invaginated cavity, and the future 
 crown is situated meanwhile as far back as 
 possible on the rudimentary head. 
 
 In contrast to this, however, the head 
 of Tctrarhynchus, &c. is said not to originate 
 directly from the first sac-like structures, 
 but to be subsequently developed in the 
 
 Fio. 218. Larva state of ... jTrT 
 
 Acanthobothrium coronatum, interior, by the base rising up into a 
 after van Beneden. ( x 25.) thimble -like projection, inside which the 
 different organs of the head are formed. " If we imagine the 
 thimble-like projection from the base of the sac broadened out above 
 like a mushroom, we have the head of a Dibothrium, which might be- 
 come a " dibothrian " Tetrarhynchus by the addition of proboscides." 
 So we read in Wagener, 1 and van Beneden says pretty much the same 
 thing, but differs in so far as he takes the Scolex-form for his starting- 
 point (see p. 329), and does not regard the head-sac as a new struc- 
 ture, but the retracted anterior end of the worm. 
 
 After the foregoing observations, it cannot be doubted that in 
 the Tetrarhynchi and the related forms the base of the originally 
 quite simple 2 head-rudiment is raised into a boss-like elevation to 
 effect the formation of the head proper. But of course that does not 
 imply that these plugs alone produce the head. This is by no means 
 proved by the preceding statements, for these all rest upon investiga- 
 tions which are quite insufficient to establish any such conclusion. 
 
 In order to study more especially the process of the formation 
 of the head, I have investigated by means of sections a number 
 of young Tetrarhynchus-l>la,dder.s from the muscle of Lophius pisca- 
 torius. The material certainly furnished me with no continuous 
 developmental succession, but it convinced me most distinctly that 
 the elevation only takes place at a time when the suctorial cups 
 and proboscides are already formed, and when the head, with its 
 different parts, is thus essentially mature. Upon the whole, the 
 conditions are quite similar to those of the typical bladder-worms. 
 
 1 Loc. tit., p. 52. 
 
 * In claiming this rudimentary head as simply a hollow bud, I do so not only on the 
 ground of Wagener's statements, but on the basis of my own investigations of Tetra- 
 rhynchus and Echinobothrium. 
 
FORMATION OF THE HEAD OF TETRARHYNCHUS. 
 
 375 
 
 FIG. 219. Longitudinal sec- 
 tion of a still imperfectly de- 
 veloped Tetrarhynchus from the 
 muscle of Lophius. ( x 25.) 
 
 As in these, the suctorial cups at first lie in the wall of the rudimentary 
 head, close in front of the posterior caecal end, so that their cavity 
 is directed inwards. Between them there 
 is as yet but a slight elevation, which 
 scarcely rises to the height of the suctorial 
 cups, and covers itself with the lower 
 muscular borders of the latter. On the 
 anterior borders of the same may be 
 noticed the opening of the proboscis- 
 sheaths, which extend back along the floor 
 of the caecum with their invaginated 
 hooks and terminal pouch, and which are 
 externally covered by the receptacle-like 
 muscular sheath surrounding the rudi- 
 mentary head. At the anterior border 
 the fibres of this sheath may be observed 
 bending round into the peripheral mus- 
 culature of the Cestode-bladder, which is filled inside with large 
 granular cells. 
 
 We thus get the same result in regard to the Tetrarhynchi as we 
 formerly did from our investigations of the Tcenice, and they may be 
 summed up thus, that it is the sac-like invagination of the bladder 
 itself which produces the head. The elevation always appears only as 
 a secondary structure of subordinate morphological importance, and 
 is, moreover, by no means so widely distributed as the statements of 
 some investigators would lead one to suppose. 
 
 All the Cestodes which we have as yet considered, in spite of their 
 other differences, agree in being provided with a well developed 
 " head," which is in form and structure in sharp contrast to the rest 
 of the body. But, besides these, there are a number of Cestodes with 
 a simple, more or less inconspicuous head, which is as a rule provided 
 with two superficially situated longitudinal pits, a circumstance 
 which has procured for these animals the name of " Dibothria." Like 
 the head, the segments are less individualised, being not unfrequently 
 indicated only by the successive repetition of the sexual organs 
 (Ligula, Tricenophorus), or even represented by a completely simple 
 body (CaryopJiyllceus, Archigetes). The genus Bothriocephalus (sensu 
 stricto) is the first of this group, the only tape- worm outside the genus 
 Tcenia which is found in man. 
 
 Such being the case, a special interest naturally attaches itself to 
 these tape-worms. All the more is it to be regretted that our experi- 
 ence of the forms in question is hitherto only slight. It is true that 
 we are acquainted with a number of young Dibothria in the higher 
 
376 THE DEVELOPMENT OF CESTODES. 
 
 and lower animals, especially in fish, which live like bladder-worms 
 in the muscles and in the parenchymatous organs, or occasionally 
 free in the body-cavity (Schistocephalus, Ligula) ; but their mode of 
 development has not been observed, or at least not traced as far as the 
 hook-bearing embryo. The only form which we must except is the 
 peculiar genus Archiyetes peculiar, because while as yet in the 
 Cysticercoid condition, or at least while still possessing the attributes 
 of an embryo, it becomes sexually mature, and that too (the only 
 example in the Cestodes *) in an invertebrate animal (Scenuris and its 
 allies). The development is further very simple in this case, for the 
 six-hooked embryo becomes transformed into the adult animal without 
 interruption or change of abode. During its continuous 
 growth it exchanges its original form for a more club- 
 like one, and by modification of the anterior as well as of 
 the posterior portion, becomes a tail-bearing worm, which 
 at first sight has a striking resemblance to a Cercaria. 
 The embryonic hooks persist at the posterior end of the 
 caudal appendage, and the modification of the embryo, 
 which has at first the usual structure, is effected mainly 
 by the distention of the segment opposite the hooks, 
 while the rest of the body preserves its slender form, 
 and ultimately grows out into a long appendage. This 
 tail-like appendage is thus the direct developmental 
 product of the six-hooked embryo. In spite of its dis- 
 similar form (we have, however, found a similar one 
 among the Tetra-rhynchi) it is homologous with the 
 bladder of the other Cestodes. Like the latter, it plays 
 in the Archigetes the part of a " head-former," for the 
 protuberance out of which the head-bearing body of the 
 worm arises might after all be regarded as a bud-like 
 proliferation, just as is the head -rudiment in the 
 bladder-worms. The fact that this bud does not grow 
 as usual inside the (increased) six-hooked embryo, but is 
 appended exteriorly, cannot constitute a difference, since 
 ,. both external and internal buds occur promiscuously 
 
 FIG. 220. Archi- . . . y . . J 
 
 gete* Sieboldi in the animal kingdom. It is true that in this case 
 
 ( x 60). there originates from the bud, not a head merely, which 
 
 afterwards forms the segmented body by new budding, but a structure 
 
 which, from the first, exhibits both head and body ; for the anterior 
 
 1 The significance of this fact, to our conception of the historical development of 
 parasitic life, has already been noted (p. 70). Compare also, regarding this interesting 
 form, Leuckart, Zeitschr. f. wiss. Zool., SuppL- Bd. xxx., p. 593, 1878, and Ratzel, 
 Archivfur Naturgesch., Jahrg. xxxiv., Bd. i., p. 138, 1868. 
 
YOUNG STAGES OF THE DIBOTHRIA. 377 
 
 end, like a head, bears the two suctorial pits, while the rest of the 
 body develops the sexual organs. What is in the other Cestodes 
 spread over two successive generations, seems in Archigeles, as well as 
 in some other forms, to be condensed into a single developmental 
 stage ; for the animal is not a colony with head and sexual animal, 
 but a simple head-bearing and sexually mature flat- worm. 
 
 According to all appearance, this is, however, not the only Cestode 
 which develops in the manner described. Wagener x tells us that in 
 TricenophoTUs, so long as it remains encapsuled in the liver of the 
 fish that is to say, lives in its intermediate host there is seen 
 attached to the thick fore-part of the body, which bears the attaching 
 apparatus (pits and hooks), a ribbon-like caudal appendage, almost 
 half as long as the entire body. Bounded in front by a constriction, 
 and very different in structure from the rest of the body, it is dragged 
 about by the motions of the animal like a lifeless mass. It is thus 
 undoubtedly a peculiar structure, and comparable to the caudal 
 bladder of the other Cestodes, in so far as it is at first destitute of the 
 fore-part of the body, and itself represents the worm. 
 
 In the other Dibothria, so far as we know, a special caudal ap- 
 pendage is never present. The embryo apparently grows by simple 
 elongation into a cylindrical or tape-like 
 worm, which then forms the attaching 
 apparatus at its anterior end, in a way A 
 which has not yet been ascertained. These jj 
 developmental processes have a general 
 resemblance to those which we formerly 
 saw to be characteristic of Eudolphi's 
 Scoleces (and other Cysticercoids), only that FIG. 221. Larva of a Bothrw- 
 in this case the share which the embryo ce P h(du8 from the smelt - 
 takes in the formation of the adult animal is much more than merely 
 structural. 
 
 In many cases the Dibothrian tape-worm attains, even in this 
 intermediate stage, a considerable size. Thus Diesing 2 describes, 
 under the name of Spargarum reptans, what was probably nothing 
 else than a larval form of Bothriocephalus, which was a foot long, and 
 occurred in no fewer than thirteen mammals, twenty-four birds, and 
 fifteen amphibians, all in Brazil. It was sometimes encysted under 
 the skin, or between the muscles, and sometimes occurred free in the 
 
 1 Loc. cit., p. 26 et seq. Zeder, however, made the same observation before Wagener 
 ( "Nachtrag zu Goze's Naturgesch. , " p. 414). He was even led by it to rank this worm 
 (as Vesicaria lucii) with the Cysticcrti. 
 
 2 DenJcschriften der Wiener ATcad., Bd. ix., tab. ii., p. 174, 1855. 
 
378 THE DEVELOPMENT OF CESTODES. 
 
 body-cavity. 1 The strap-worms (Ligula} which inhabit the body- 
 cavity of our freshwater fish attain a still larger size, and also ad- 
 vance further in development, since they form their sexual organs 
 while still in their intermediate host. The same is true of the 
 Schistocephalus of the stickleback, which is, upon the whole, very 
 nearly allied to the strap-worms, and is indeed only distinguished 
 from them in this, that the tape-like body is externally jointed, and 
 that this segmentation takes place during the larval state. 2 
 
 It will thus be understood that the hosts of the Ligulidae are 
 endangered in a high degree by the growth of their parasites. In 
 nearly every case their parasitism results in a chronic peritonitis, to 
 which large numbers of fish fall victims. There are even distinct 
 instances of epidemics being caused by these worms, and especially 
 by Ligula* 
 
 It might, however, be doubted whether the Ligulidae live from 
 the first in the body-cavity. At any rate one finds not unfrequently 
 in the liver of their host Helminth -capsules, enclosing a young, still 
 undifferentiated, Cestode of simple shape, which might quite well be 
 the larval form of Ligula or Schistocephalus. In this case trans- 
 ference into the body-cavity would of course soon follow, since only 
 a few weeks after infection with ciliated embryos (apparently intro- 
 duced through the intestine, and not through the skin) Donnadieu * 
 found young strap -worms in the body-cavity. Although some of 
 them were only from six to seven millimetres long, they possessed 
 essentially their subsequent structure. 
 
 So far as we know, there is no other Cestode besides Archigetes 
 which completes its development without interruption or change of 
 host, or, what is the same thing, becomes sexually mature in its first 
 host. 5 And we can indeed hardly count Archigetes an exception, 
 
 1 From the manifold nature of the hosts alone it is very improbable that all these 
 worms belong to the same species (see p. 12). 
 
 9 It is true that when we remember that the true Ligulidae, and especially the still 
 small young specimens, also exhibit distinct traces of segmentation, this difference becomes 
 only one of degree. 
 
 * See Donnadieu, " Contributions a 1'histoire de la Ligule," J&urn. anat. et phy&iol., p. 
 321, 1877. 
 
 * Loc. cit., p. 452. 
 
 * Even on this ground the assertion of Knoch that, in the human intestinal canal, 
 Boihriocephalus latus develops from the six-hooked embryo (even from the undeveloped 
 egg ! ) directly into the later tape-worm, has only slight probability. When describing 
 the worm more specially we shall afterwards return to the views and experiments of this 
 author (" Naturgesch. des breiten Bandwurmes," Mem. Acad. St. Petersb., t. v., No. 5, 
 1862), but it may now be mentioned that the experiments on which Knoch founds his 
 assertion have by no means the cogency which he fancies. [Braun of Dorpat has 
 shown experimentally, as we shall see hereafter, that Bothriocephalus latus has an inter- 
 mediate host in its young stage, just like other Dibothria, and that its larva is transferred 
 
TRANSITION TO THE ADULT STATE. 379 
 
 merely because it attains in the Cysticercoid condition that maturity 
 which is in other cases only reached at a later stage of development 
 wanting in Archigetes. In order to attain this definitive developmental 
 stage the tape-worms must be transferred from their former host to 
 some other suitable animal. Along with their hosts, or with the 
 portions which they inhabit, they are imported into the intestine of a 
 new host, where, after greater or less alterations, they become adult 
 tape- worms. "With the exception of Archigetes, the sexually mature 
 Cestodes occur only in the vertebrates. 
 
 The transition into the sexually mature worm occurs most simply 
 in the Ligulidse, which, as larvae, are already comparatively mature, and 
 have their sexual organs even then almost completely developed. 
 Twenty-four hours after they have passed into the intestine of a duck 
 or some water-bird, one finds them with eggs fully developed, pro- 
 vided of course that they previously possessed the requisite differen- 
 tiation and size (at least 10 cm.). 1 In other cases the worms are 
 digested, or are expelled unchanged with the faeces. Even in their 
 sexually mature state the Ligulidae remain but a few days in the 
 alimentary canal of the bird ; after the course of a week or even earlier 
 they succumb to the same fate as the larval forms, being either 
 expelled or altered by digestion, which first affects the posterior end. 
 Donnadieu estimates the average duration of the parasitism of 
 Ligulidse only at two and a half days. In water of ordinary tempera- 
 ture these animals remain living for eight or ten days. As regards 
 their external appearance, the only change on the acquisition of 
 sexuality is the considerable elongation and narrowing of the body. 
 
 In the case of the isolated Tetrarhynchus-heads, the progress of 
 events is somewhat more complicated. After they have been trans- 
 ferred, along with their intermediate host, into the alimentary 
 canal of a shark or ray, the passage into the final stage is accom- 
 
 to man from fish, especially the pike. R. L.] I may also remark that Megnin and Moniez 
 have lately maintained for the Tcenice a continuous development without change of host 
 and without cystic state a supposition based essentially on the fact that the number of 
 known bladder-worm forms is much too small in proportion to the great number of the 
 existing species of tape-worms. They forget that the tape-worm hosts often devour 
 hundreds of animals before they find a bladder-worm host ; in other words, that the 
 bladder-worms are very sparsely distributed, especially in the lower animals, and therefore 
 often escape our investigation. At any rate this assertion is not worthy of much con- 
 sideration until it is established by direct observations. 
 
 1 See Donnadieu, loc. cit., and Duchamp, Ann. sci. not., t. vii., No. 7, 1876. The 
 latter observed the attainment of sexual maturity even in some worms transferred experi- 
 mentally into the body-cavity of a dog (Comptes Rendus, t. Ixxxvi., p. 493, 1878). It can 
 therefore hardly be doubted that it is primarily and principally warmth which brings them 
 to ripeness ; nor is it necessary to have the whole worm even separate pieces become ripe 
 in the intestine of the bird. 
 
380 THE DEVELOPMENT OF CESTODES. 
 
 plished by means of the growth and segmentation of the cervical 
 portion adherent to the head, by a process, therefore, which gives the 
 parasite an entirely new stamp, and converts it 
 indeed into a perfect tape-worm. Kudiments of 
 this segmentation are even often to be seen during 
 the stay of the parasite within the intermediate 
 host. Thus at least in a Tetrarkynchus-hea.d from 
 the gills of Lepidopus, which in some points recalled 
 T. lingualis, but measured only 4 mm., I observed 
 that the neck, in spite of its perfectly simple ex- 
 ternal appearance, was also characterised by a dis- 
 tinct segmentation resulting from the internal 
 olT_ Lon ' arran g emen t especially of its vessels and muscles, 
 tudinal section of an In thin longitudinal sections I could count about 
 two dozen narrow segments, which gradually 
 became somewhat longer posteriorly, and even 
 revealed the first traces of the sexual organs. 
 
 But it is not only the isolated Tetrarhynchus-hesids which grow into 
 the future tape-worms in this directly simple fashion. The same may 
 be said of the worms formerly described as Scoleces, and of all those 
 Cestodes which are in their larval state destitute of a histologically 
 differentiated caudal bladder, as also of a few Cysticerci like C. Tcenia?. 
 cucumerince and C. cyclopis, and yet again of Bothriocephalus, &c. In 
 all these the modifications in the course of the passage into the final 
 state are in all probability restricted to an elongation and segmenta- 
 tion of the * body " which is attached behind the proper " head." But 
 if the supposition be correct, that the former is nothing but the body 
 of the embryo which has formed a " frame for the head," then the 
 embryonic body has in these cases its share in the formation of the 
 jointed worm much in the same way as in the Ligulidae. The growth 
 and jointing take place, indeed, sometimes in the definitive, sometimes 
 in the intermediate host ; but the difference which is here expressed 
 cannot be ranked as a very weighty one, especially since we find 
 numerous examples, especially among the Nematodes, where the 
 parasites do not by any means always reach the same degree of 
 development within their various primary hosts. 
 
 In the other Cestodes, i.e., in all those which are in their larval 
 state provided with a differentiated caudal bladder, whether "dropsical" 
 or parenchymatous, the metamorphosis into the tape-worm proper is 
 less direct, for the growth and jointing of the body is always pre- 
 ceded by the loss of the bladder. 
 
 We owe our knowledge of these metamorphoses to the above 
 quoted (p. 332) memoirs of Kuchenmeister and v. Siebold (or Lewald). 
 
LOSS OF THE CAUDAL BLADDER. 381 
 
 By their experiments, which were mostly made with genuine bladder- 
 worms, and especially with Cysticercus pisiformis of the rabbit, we 
 know that the separation of the bladder begins very soon after the 
 transference of the bladder-worms into their final host, and is complete 
 when they have passed (in about five or six hours) from the stomach 
 to the small intestine, where the now evaginated head becomes fixed 
 by its attaching organs. As to the nature of the process there can be 
 little doubt. The separation is an actual digestion which has natu- 
 rally its first and greatest effect on the caudal bladder, since this pre- 
 sents so large a surface to the action of the digestive juices. This can 
 take place even outside the living organism, as I have elsewhere 
 shown, * for the process may be induced by an artificial digestion. For 
 this purpose I used the fresh stomach of a dog, into which 1 trans- 
 ferred the bladder-worms, and then exposed it to the warm moisture 
 of an incubating apparatus. 
 
 The experiment is not without interest, since it enables us to 
 watch the worms in the full possession of their vitality. As a rule 
 the bladder- worms appear as extremely sluggish creatures with hardly 
 perceptible motion. But when the 
 moist warmth acts upon them, one 
 notices a lively peristalsis in the 
 bladder, and a protrusion of the body, 
 and can often observe the head pushed 
 out, feeling in all directions, and 
 may even notice how the suckers and 
 the apicial rostelluin extend themselves 
 like tentacles, and then again retract. . FIG 223 -Head of Tamia 
 
 from the intestine of a rabbit, showing 
 
 Ihe same phenomena may be various phases of motion, (x 25.) 
 observed on the isolated bladder-worm heads, when one takes them 
 from the intestine of a newly killed animal (Fig. 223). They persist 
 until the loss of warmth puts a stop to the lively motions. 
 
 After the digestion of the bladder in the stomach of the animals 
 under experiment, that is to say, after the lapse of about five hours, 
 only the cylindrical body and the head are left. The latter is usually 
 not stretched out until the worm passes to the small intestine ; adher- 
 ing to the posterior end of the body of the worm, one usually finds a 
 few half-digested remains of the caudal bladder. 
 
 Hitherto it has been commonly believed that this body, after the 
 loss of its adherent shreds, passed directly, by solidification and joint- 
 ing, into the* future tape-worm body. 2 In the first edition of this 
 
 1 "Blasenbandwurmer," &c , p. 156. 
 
 2 According to Kuchenmeister ("Parasiten," 2d ed., pp. 72 and 96) this worm body. 
 ( = " Brutkapsel," Kiich.) furnishes only the " primary terminal joint of the colony." 
 
382 
 
 THE DEVELOPMENT OF CESTODES. 
 
 work I myself expressed this opinion, but have been convinced 
 by repeated experiment that this structure disappears as completely 
 as the caudal bladder. This indeed occurs some hours later, when the 
 worm has reached the small intestine, but this is readily explained by 
 the greater resistance offered by the more parenchymatous structures 
 to the action of the digestive juice. 
 
 Thus, of the original worm only the head with its long narrow 
 neck remains, 1 and produces by its metamorphosis the jointed tape- 
 worm. And this is not the case only in the ordinary bladder-worms, 
 
 FIG. 224. Metamorphosis of the bladder-worm of the rabbit into the young tape- 
 worm. ( x 4.) 
 
 but also, according to my observations, in Cysticcrcus fasciolaris, 
 although in this case the appendage has even in the bladder-worm 
 stage grown out into a long, jointed, tape-worm body (Fig. 202). 
 
 Posteriorly, where the neck passed into the appendage, there 
 may at first persist a few traces of the former body of the worm, but 
 these vanish within twenty-four hours after the transference of the 
 bladders, and then only a small, almost scar-like, notch is left to recall 
 the former state. The scar can be detected on the terminal joint of 
 the chain till the latter is liberated. It leads into a small bladder- 
 like cavity (Fig. 228), the porus terminalis, which receives the four 
 longitudinal vessels. The cavity which formerly penetrated the 
 head and neck has disappeared through the coalescence of the opposite 
 surfaces, and thus sections already show the subsequent condition 
 of the parenchymatous sheath. The musculature of the receptacle has 
 not the slightest share in filling up the head. 
 
 In the Cysticercoids, whose anterior portion consists entirely of 
 head and neck, the caudal bladder alone is lost. It is doubtful whether 
 the same may be said of those forms whose caudal bladder is destitute 
 of any histological differentiation. Judging from the analogy of the 
 Echinococcw-he&ds, it is possible that the bladders may persist, as 
 has been hinted at above, and pass directly by segmentation into the 
 adult tape-worm. 
 
 1 With this agree the results of Moniez, as stated in his essay on the history of the 
 bladder-worm, which has just appeared. 
 
NUMBER AND DEVELOPMENT OF THE SEGMENTS. 383 
 
 The elongation and segmentation of the cervical portion 1 is as a 
 rule perceptible after a very short time. In Tcenia serrata I have 
 usually been able to distinguish with the naked eye, within forty-eight 
 hours of the feeding process, a chain of from twelve 
 to eighteen joints. In other cases, however, not a 
 trace of the segmentation was visible even after four 
 days. Sometimes one finds, even in the second or 
 third week, only a few straggling joints in a tape- 
 worm perhaps a foot long. 
 
 As to the ways and means by which the indi- 
 vidual joints gradually grow and become sexually 
 mature, we shall have much to say in our detailed 
 survey. Here we shall only note that the youngest 
 and smallest joints always lie next the head, 2 and FlG - 225. Tcema 
 
 ^ ' serrata twenty hours 
 
 only become mature after they have been pushed out old, with incipent seg- 
 to some distance from their point of origin. 3 On the mentation - ( * i<>.) 
 other hand, the smallest, even microscopic, joints show essentially 
 the subsequent musculature, though individual bands may be un- 
 equally developed. The main mass of parenchyma consists, of course, 
 of distinctly nucleated cells, which multiply rapidly, and pass subse- 
 quently into the connective tissue ground-substance, or into the 
 various generative organs. For the latter purpose, the cells group 
 themselves in strands or masses, and either directly form the repro- 
 ductive material, or, through the formation of an inner cavity, become 
 epithelial (endothelial) structures, which occasionally acquire a more 
 or less firm cuticular layer. 
 
 We have already seen some instances of the way in which the 
 form and independence of the joints may vary, and the same manifold 
 
 1 I speak purposely of the " segmentation of the neck," for the widely prevalent 
 opinion that the joints arise through budding is strictly speaking incorrect. The 
 joints are not produced by buds, that is to say, not by portions which are appended to the 
 parts already present, and which develop without their participation ; they arise by the 
 growth and modification of parts already present (the so-called "neck "), as has been 
 shown above (p. 380) in the case of Tetrarhynchus, and as may be similarly, though less 
 conspicuously, demonstrated in the case of Tcenia. 
 
 2 Here I ought perhaps to refer to Moniez's opinion, according to which (Bull. sci. 
 dep. du Nord, p. 293, 1879) the head of the tape-worm represents not the anterior, but 
 rather the posterior end of the body. Moniez regards the tape-worm as a simple animal, 
 and denies the existence of an alternation of generations, and is able by means of the above 
 theory to remove the difference between the tape-worms and the segmented worms, as 
 regards the position of the buds, which, as is well known, are in the latter always before 
 the anal segment. 
 
 8 [The first formed joints are very commonly, though to a different extent in diverse 
 species, sterile, and smaller than the later ones. Where they are numerous, as, e.g., in 
 Tcenia perfoliata, the appearance of the young colony is so different from that of the 
 older, that they have been regarded as different species. Thus, Tcenia plicata, Auct., is 
 only the young stage of T. perfoliata with a large number of sterile joints. R. L.J 
 
384 THE DEVELOPMENT OF CESTODES. 
 
 differences obtain in regard to their number. We know tape-worms 
 with only three or four joints, and some with as many thousands, hence 
 the period of a joint's development must also vary greatly. In the 
 larger tape- worms, several months pass before the first joint is libe- 
 rated, while in other cases only a few days are required. 
 
 At first sight it looks as though the head remained almost un- 
 changed, and was only of importance in the formation of the chain in 
 so far as it furnished, as it were, the raw material for the latter ; but 
 this view is not confirmed by closer observation and comparison, 1 
 for not only does it grow for a while in its Tsenioid state, but its 
 hooks often become larger and thicker by the deposition of new 
 chitinous matter on the roots and on the base. The changes are 
 indeed usually but slightly marked, so that they escape observation 
 in the majority of cases. Tcenia echinococcus is, however, an excep- 
 tion, since the differences in the size and shape of the hooks at 
 different stages are so striking that for a while they caused perplexity 
 in the study of the nature and life-history of the form in question. 
 Among the Bothriadse also we know of a form (Echineibothrium) 
 which does not complete the development of its armature till it 
 reaches the tape-worm stage. 
 
 In all cases the metamorphosis of the bladder-worm into the tape- 
 worm takes place only after the transference of the former into the 
 intestine of a suitable host. In its original abode the bladder- worm 
 remains what it was. It grows to a certain size, and may live on 
 perhaps for years, but a further development is impossible in this 
 environment. 
 
 As to the age which bladder- worms as such may attain, we have as 
 yet but few results, and what we have relate only to the forms found 
 in vertebrates. The Echinococcus is credited with the longest life. 
 We know of individuals who have suffered from this parasite for 
 thirty years and more. A deduction from this as to the other bladder- 
 worms is, however, illegitimate, for in Echinococcus we have to do, not 
 with single individuals, as in the Cysticerci, but with generations, of 
 which the oldest have long since perished, while the young forms are 
 
 1 This would be still more evident, if it be true, as Megnin has just asserted (Comptes 
 rendus, t. xc., p. 715, 1880), that after a longer or shorter existence the head loses 
 its hooks and suckers, and is finally so thoroughly absorbed that only the chain of 
 joints remains. In this acephalous state the latter persists till the youngest joint is ripe, 
 and the life of the tape-worm thus comes to an end. This has indeed been observed by 
 Me'gnin only in a few species (Tcenia infundibuliformis of the fowl and Tcenia lancedata 
 of the goose), but he does not hesitate to infer that the same may be true of the other 
 species, though the length of life is often very long. [In this connection we may not un- 
 fitly recall the curious Idiogenes otidi* of Krabbe ( Vid. Meddel. nat. Foren. Kjobenhavn, 
 p. 122, 1867), one of the Tseniadae, which is known to be headless and possessed of a very 
 peculiar anterior segment R. L.] 
 
DEATH OF THE BLADDER- WORM. 385 
 
 ever forming themselves anew. It is probable that the ordinary 
 bladder- worms do not usually persist in their hosts more than a few 
 years. 
 
 In the examination of measly animals one sometimes finds 
 specimens with protruded head, which have a very turbid, withered 
 appearance, and exhibit no signs of life. When the surrounding cyst 
 is unmodified, one may plausibly conclude that the parasites have 
 died a natural death. As a rule, however, the cause of death must 
 be sought in the pathological state and modification of the surround- 
 ing connective-tissue capsule. In such cases the secretory activity of 
 the capsule has probably been in some way altered. Indeed one 
 sometimes finds not only cysts whose under surface has an abnormal 
 character perhaps strongly injected or covered with small prolifera- 
 tions but also others which have a bloody or even purulent fluid 
 next the worm. 
 
 When the worm dies, whether from internal or external causes, 
 its body-parenchyma at once begins to get turbid, and its bladder-fluid 
 to be absorbed. The latter is gradually thickened, and acquires an 
 almost gummy character. Afterwards the worm undergoes the same 
 changes as may be observed in foreign substances introduced into 
 the body-cavity. As the body of the worm becomes more and more 
 shrivelled up and deformed, the albuminoids become displaced by a 
 fatty mass which fills the collapsed connective-tissue cyst, and is 
 finally calcified by the deposition of lime salts in varying abundance. 
 On closer examination one often finds inside such cysts the still un- 
 changed tape-worm hooks, which most indisputably prove the origin 
 and nature of the apparent pseudoplasms. 
 
 In some cases these changes undergone by the dead bladder-worm 
 exhibit various, but little studied, divergences. Thus there is in the 
 pathological collection at Giessen a Cysticercus tenuicollis whose caudal 
 bladder not the cyst, as one might sooner have expected is calcified 
 all over, and seems almost ossified, without the form being at all 
 altered. 
 
 Having now discussed the development of the tape-worms in its 
 most important modifications, let us cast a glance at their life- 
 history. Five successive stages are to be noted : (1.) the six-hooked 
 embryo ; (2.) the bladder- worm or Cysticercus ; (3.) the tape-worm 
 head without joints (Scolex) ; (4.) the proper chain -like worm (Strobila); 
 and (5.) finally, the isolated sexual animal or Proglottis. The life- 
 history of the Cestodes is therefore much richer and more complicated 
 than we usually find even among the lower animals. 
 
 On closer examination these five phases are reduced to three 
 different forms, the round embryo, the tape-worm head, and the 
 
 2 B 
 
386 THE DEVELOPMENT OF CESTODES. 
 
 sexual segment. These three forms represent as many generations, and 
 all three form together a life-cycle. We have already given reasons 
 for regarding the two latter forms as individuals, and the claims of 
 the six-hooked embryo will be doubted by no one who considers its 
 history without bias. The sexual animal results by asexual reproduc- 
 tion from the tape-worm head, and remains for a period in union with 
 it, forming the worm-chain or Strobila. In the same way the tape- 
 worm head has its origin in the embryo. The manifold metamorphoses 
 undergone by the latter do not in any way affect its individuality. 
 The caudal bladder of the Cysticercus is, like the homologous Eckino- 
 coccws-bladder, a morphologically independent structure ; it stands in 
 the same relation to the tape-worm head as the latter to the sexual 
 animal. Like the jointed tape-worm, the typical bladder-worm is 
 morphologically not a single individual, but a colony, with joints at 
 different stages of development. 
 
 Of the three different generations which are distinguishable in the 
 Cestode life-cycle, only one the Proglottis is sexual. Both the others 
 are preparatory, and have only the power of asexual reproduction. 
 
 The life-history of the Cestodes seems, therefore, to be an alterna- 
 tion, with two " nurse " forms one a " nurse " in the proper sense of 
 of the term, the Scolex, the other a " grand-nurse " (Grossamme), the 
 six-hooked embryo. 
 
 We should, however, be doing violence to nature if we tried to 
 apply this formula rigidly in all instances. For, besides the forms 
 in which we can observe the three successive generations in sharp and 
 distinct contrast, there are others in which these developmental stages 
 have so little independence, and follow one another so gradually, that 
 it is impossible for us any longer to credit them with distinct indi- 
 viduality. The structural variations, elsewhere spread over different 
 generations, appear in these cases merely as developmental phases 
 of the same individual: the alternation of generations is replaced 
 by a metamorphosis. 
 
 We have in the course of. our survey noted many of these cases, 
 some where it was impossible to distinguish nurse and grand- 
 nurse as individualised structures, and others where nurse and 
 sexual animal were bound up in one. The Scolex-foruis may suffice 
 for illustration of the former case, and Archigetes of the latter. 
 Perhaps we should also regard the Ligulidse as forms in which the 
 three otherwise separate generations are condensed into one, so that 
 we cannot speak of an alteration of generations. 
 
 In the light of the many surprising results of the study of animal 
 development, these facts do not seem specially unique. We know how 
 in the lower animals the "individual" has often only a restricted 
 
CONCLUDING REMARKS ON DEVELOPMENT. 
 
 387 
 
 independence, and is physiologically subordinated to the rank of an 
 organ. We know also that between reproduction and growth no sharp 
 definite boundary line can be drawn ; that, in other words, the phases 
 and phenomena which we are wont to denote as individuals and as 
 reproduction, have a certain adaptive mutability, and have only 
 gradually acquired their characteristic properties. And thus we must 
 not be astonished when we find that conceptions, usually sufficient, 
 are not universally applicable ; that an alternation of generations may 
 be condensed into a simple metamorphosis ; and a metamorphosis may 
 spread over several successive individuals so as to constitute an alter- 
 nation of generations. 
 
 It is not the Cestodes alone which furnish us with examples of 
 this sort ; we find others, some of them still more striking, among 
 other animals, such as the Coelenterata, where the group of the Hydro- 
 medusae, or jelly-fish, furnishes us with most convincing proofs of the 
 correctness of our conception. 
 
388 SYSTEMATIC ACCOUNT OF THE CESTODES. 
 
 SYSTEMATIC ACCOUNT OF THE CESTODES. 
 
 Rudolphi, "Entozoorum s. verm, intest. hist, nat.," 1808-1810. 
 
 Fr. S. Leuckart, " Zoologische Bruchstiicke," Heft i., 1819. 
 
 Dujardin, "Hist. nat. des Helminthes : " Paris, 1845. 
 
 Van Beneden, " Vers Cestoides," Mtm. Acad. Sci. Bruxdles, t. xxv., 1851. 
 
 It is not only in regard to the life-history and development of the 
 Cestodes that our knowledge has increased in scope and complete- 
 ness ; the same must be said of our knowledge of the different forms 
 and their natural relationships. 
 
 Apart from the bladder-worms and certain more isolated species, 
 such as Liyula, the older naturalists knew only a single genus of 
 tape-worms, Tcenia. It was, therefore, an important step when 
 Rudolphi not only increased the number of the unsegmented tape- 
 worms by the erection of different genera (Caryophyllceus, Tricuspidaria), 
 but also separated a number of species from Tcenia on the ground of 
 the structure of the head (foveis dudbus instead of osculis quotum 
 suctoriis), and formed them into a special genus, Bothriocephalus. 
 Although Rudolphi himself, in his later writings, prepared the way 
 for the further breaking up of this family, by establishing a group of 
 Rhynchobothrii (i.e., TetrarhyncM grown into tape- worms), it remained 
 for long with its original content. This persisted, indeed, until van 
 Beneden made us acquainted with the manifold Cestode forms para- 
 sitic in rays and sharks, and was not only compelled by his ex- 
 tended knowledge to erect numerous new genera, but made, for the 
 first time, an attempt towards a natural division of the group, which 
 henceforth included also the bladder-worms. 
 
 Van Beneden distinguished four families of tape-worms, distin- 
 guished according to the number and structure of their suckers : the 
 Tetraphylles, Diphylles, Pseudophylles ( = Bothriocephali sensu stricto), 
 and Aphylles (Teniens). It seems doubtful whether the group Diphyl- 
 lidia, which is only represented by a single genus, Echineibothrium 
 (Fig. 226, B), should be retained ; I should rather divide the Tetra- 
 phyllidia into Rhynchobothria and Phyllobothria, so that the Cestodes 
 would then fall into the four groups Rliyncliobothria (Tetrarhynchi 
 Phyllobothria, Tceniadce, and Bothriocephali (or Dibothria). 
 
 The Rhynchobothria (Fig. 226, A) have a large head with four long 
 proboscides and four large suckers, which often coalesce in pairs. 
 
 The Phyllobothria have four rarely two large, moveable, and 
 often very complex suckers, sometimes furnished with spines anteriorly, 
 and sometimes without armature. 
 
VAN BENEDEN'S CLASSIFICATION OF THE CESTODES. 
 
 389 
 
 The Tceniadce are characterised by the want of a special uterine 
 opening, and more especially by the possession of four simple 
 suckers, between which on the apex there is usually one complete 
 circle of hooks, but sometimes more. 
 
 FIG. 226. 
 
 Tetrarhynchus 
 
 sepice 
 (isolated head). 
 
 (x 12.) 
 
 L 
 
 Bothriocephalus latus 
 
 (cephalic end). 
 
 (x8.) 
 
 Tcenia 
 
 echinococcus. 
 
 (x 10.) 
 
 Eckineibotlirium minimum 
 (after van Beneden). ( x 8.) 
 
 In the BothriocepJialidce the attaching apparatus is reduced to two 
 longitudinal grooves, which have only a slight mobility, and some- 
 times become so shallow that they can hardly be regarded as inde- 
 pendent structures. Only in a few cases do we find hooks at the 
 anterior end. The segmentation is often indistinct, and sometimes 
 wholly disappears, so that the whole body forms one united mass. 
 
 Man is infested by various species of Cestodes belonging to the two 
 families of the Tseniadse and Bothriocephalidse. The majority belong to 
 the former of these families, which is indeed most widely distributed 
 among terrestrial animals. The human Taenioid parasites in the adult 
 stage are Tcenia saginata (T. mediocanellatct), T. solium, T. cucumerina, 
 T. nana, T. flavomaculata, and T. madagascariensis, 1 - some of which, 
 
 1 According to Heller (" Darmschmarotzer," in Ziemssen's " Handbuch d. spec. Pathol. 
 u. Therapie," Bd. vii., 2, p. 560), there is in the Pathological Institute at Erlangen 
 another still undetermined Tcenia, which was voided by a child. 
 
390 SYNOPSIS OF THE TVENIAOffi. 
 
 indeed at least T. cucumerina are only to be regarded as occasional 
 visitors. They are found exclusively in the small intestine, which 
 they share with two Bothriocephali B. latus and B. cwdatus. 
 
 But it is not only adult Cestodes which are found in man. He 
 also harbours a number of Tsenioid bladder- worms, viz., Cysticercus 
 cellulosce (of T. solium), Cysticercus acanthotrias (of T. sp. ?), Cysticercus 
 tenuicollis (of T. marginata) though this is not beyond doubt and 
 the Echinococcus (of T. echinococcus). Some of these grow to a very 
 considerable size, and occasion manifold dangers, from which hardly 
 any organ is exempt. Specially important, however, are the 
 Echinococcus, Cysticercus cellulosce, Tcenia saginata, T. solium, and 
 Botliriocephalus latus. 
 
 The following synopsis shows the systematic arrangement of the 
 forms treated of in the present volume : 
 
 FAMILY 
 Genus 
 
 Division I. Cystici. (Cystic Tape-worms.) 
 Sub-genus Cystotccnia, Leuckart. 
 
 1. Tcenia saginata, Goze (Tceniarhynchus, Weinland). 
 
 2. Tcenia solium, Kudolphi (Cystotcenia sensu stricto). 
 
 3. Tcenia acanthotrias, Weinland. 
 
 4. Tcenia marginata, Batsch. 
 
 Sub-genus JZchinococcifer, Weinland. 
 
 5. Tcenia echinococcus, v. Siebold. 
 
 Division II. Cystoidei. (Ordinary Tape-worms.) 
 Sub-genus Hymenolepis, Weinland. 
 
 6. Tcenia nana, v. Siebold. 
 
 7. Tcenia Jlavo-punctata, Weinland. 
 
 Sub-genus - ? 
 
 8. Tcenia madagascariensis, Davaine. 
 
 Sub-genus Diphyllidium, Leuckart. 
 
 9. Tcenia cucumerina, Kudolphi. 
 
FAMILY T^NIAD^E. 
 
 391 
 
 FAMILY I., 
 
 The small pear-shaped or spherical head bears, at some distance from 
 the apex, four roundish suckers, which are situated at tolerably equal 
 distances from one another, and possess a powerful musculature of their 
 own. Between the suckers there is usually, near the apex, a simple vr 
 manifold circle of claw -like hooks. To support and move the latter, 
 there is a capsular muscular apparatus the rostellum which pro- 
 trudes more or less from the crown of the head, sometimes even resembling 
 a proboscis, which can also be retracted. 
 
 The proglottides are distinctly separated from one another ; in their 
 adult state they are usually longer than broad, and are almost always 
 provided with marginal generative openings, 
 sometimes confined to one side, sometimes alter- 
 nating irregularly on both sides. In some cases 
 also the joints have a pore on either side. The 
 number of sexual joints varies greatly (from three 
 up to three or four thousand} ; the length of the 
 adult tape-worm is, therefore, also subject to much 
 variation. The liberation of the proglottides takes 
 place with great regularity, but somewhat late, 
 after the embryos are almost fully formed. The 
 uterus has no direct communication with the 
 exterior, so that the eggs remain inside the pro- 
 glottides, and are only set free when these are 
 destroyed. 
 
 The yolk -glands are but slightly developed. 
 During development the embryos, while increasing 
 continually in size, become surrounded with an 
 often multiple envelope of more or less firmness. 
 
 Since the transference of the eggs into the uterus FIG. 227. Head of Tcmia 
 is restricted to a comparatively short time, one sohum - ( x 35 -) 
 finds them almost all at the same stage of development. 
 
 In the adult state the Tseniadee live especially in terrestrial animals 
 mammals and birds while the larval forms (bladder- worms, or 
 Cysticerci) are found in very diverse higher and lower animals. They 
 possess, with few exceptions, a well differentiated caudal bladder, 
 but show manifold peculiarities as regards their proliferation. Some- 
 times they form distinct polycephalous colonies. Those occurring in 
 the mammals usually attain a considerable size, which is largely due 
 to the copious accumulation of watery fluid in the bladder. 
 
392 
 
 FAMILY TVENIAD.E. 
 
 Specially characteristic are the varied peculiarities exhibited by 
 the organs of attachment. So distinctive are they, that one can, even 
 with a hasty glance, recognise the Tseniadae and distinguish their 
 different species. This is of course true, especially of the forms 
 armed with hooks, but even those with suckers only are readily 
 recognised. 
 
 In details the armature varies exceedingly. The hooks which 
 compose it have a conical form, and have their points turned back- 
 wards ; but in size and number, shape and arrangement, they vary so 
 much and so strikingly, that almost every one of the nearly two 
 hundred species has its own characteristic appearance. Just to 
 suggest the range of these variations, I may mention that the number 
 varies from eight to several hundreds. Krabbe counted 360 in a 
 Tccnia from the emeu, and even 860 in a form found in the quail. 
 Their size varies from 04 mm. (T. crassicollis) to 0*01 
 mm., and even less, so that sometimes the embryonic 
 hooks may be larger than those of the adult. If the 
 number be small, then the hooks stand usually in a 
 single circle, but are as a rule in a double, or sometimes 
 even in a triple or quintuple ring. In many cases, the 
 double ring looks very like a single one, owing to the 
 minuteness of the intervening space. The hooks of the 
 second row alternate with those of the first, and are 
 usually distinguished by smaller size and different 
 shape. Sometimes the hooks of the posterior row differ 
 in number from the others. 
 
 The hooks are attached by a sort of root, which is 
 sunk into the cuticle of the head. It is usually laterally 
 compressed, and produced forwards and backwards 
 into a more or less conspicuous process. The hinder is 
 always turned towards the crown of the head, and is 
 generally the longer, though in some species the reverse 
 holds true. In the angle between the two root-pro- 
 cesses, which of course belong to the same radius, the 
 above-mentioned rostellum is fixed, so that the hooks 
 FIG. 228. Lon- are> in a certain sense, seated upon the latter. 
 of^young^S This rostellum is the most important, if not the 
 scrrata, consist- on iy motor apparatus which the hooks possess, special 
 tirelyofheadaTd muscles attached to the root-processes being, as a rule, 
 neck. ( x 60.) wanting in the Tcenicc. The rostellum has the form of 
 a sometimes lenticular, sometimes oval or cylindrical bulb, of a more 
 or less powerful muscular character, and able, according to its form 
 and state of contraction, to exert pressure either on the posterior or 
 
STRUCTURE OF THE ROSTELLUM. 393 
 
 on the anterior root-process, in consequence of which the hooks are 
 respectively retracted or erected. 
 
 The rostellurn is in principle very like the proboscis of the 
 Echinorhynchi, only that the latter has on the whole a more powerful 
 development, and is able to exhibit much more effective movements. 
 This resemblance is not, however, always equally evident, as a closer 
 examination will show us. 1 
 
 I regard as the simplest form of this rostellum that which is found 
 in Tcenia cucumerina of the dog and cat (= T. elliptica, Auct.). It 
 consists of a closed sac, which, when quiescent, has an oval form, 
 and is longitudinally embedded in the crown of the head in such a 
 way that the anterior segment, which bears the hooks, protrudes like 
 a boss ensheathed by the cuticle. The boundary of the sac is formed 
 of a structureless membrane, which is 
 possessed of considerable elasticity, 
 and is firmly connected with the sub- 
 jacent musculature. The latter is 
 composed of two kinds of fibres some 
 circular, which surround the posterior 
 two-thirds of the sac, and which lie, 
 therefore, behind the hooks, and some FIG. 229. Rostellum of Tcenia 
 longitudinal, which belong exclusively cumeri, (x HO.) 
 
 to the anterior portion, and run from the circular muscles, con- 
 verging towards the apical surface of the sac. The interior of the 
 sac is filled with a somewhat soft, clear, connective substance, which 
 is penetrated by a network of fine fibres, and encloses numerous 
 nucleated cells. 
 
 These two groups of muscles are obviously to be regarded as antago- 
 nistic. By the contraction of the circular fibres, the posterior half of 
 the rostellum is constricted, and instead of cylindrical it becomes 
 club-shaped, owing to the accumulation of connective substance in 
 the thereby distended anterior end. The hooks are forced to change 
 their position on the now more strongly curved surface ; if the 
 pressure, as one would expect, be greater on the posterior root- 
 processes, which are directed towards the apex, then the points of the 
 hooks must move backwards and therefore sink in. When the cir- 
 cular muscles are again relaxed, the longitudinal fibres 2 empty the 
 
 1 As to the structure of the rostellum, see, in addition to Leuckart ( " Blasenband- 
 wurmer," p. 63, note), also especially Nitsche, Zeitschr. f. wiss. Zool., Bd. xxiii., p. 181, 
 and Steudener, Abhandl. naturf. Gesettsch. Halle, Bd. xiii., p. 408, 1877. I must, how- 
 ever, note that I am not able entirely to agree with Nitsche's conclusions, especially in 
 this, that I regard the ' ' elastic cushion " of the cystic tape-worms as muscular, and as 
 in reality forming the rostellum. 
 
 2 In spite of their somewhat divergent insertion, these retractors plainly represent the 
 
394 FAMILY 
 
 anterior end, and produce a uniform distribution of the connective 
 substance, and by the re-assumption of the former cylindrical shape 
 relieve the root-processes from their pressure. If the muscles act 
 more vigorously, then the arched anterior end of the rostellum may 
 even become more or less deeply depressed, so that any effect on 
 the position of the hooks is removed. 
 
 With the movements of the hooks is usually associated a pro- 
 trusion of the rostellum itself, which is, of course, accomplished 
 by the surrounding muscular masses. Especially important are the 
 longitudinal body-muscles, which can be traced into the head, and 
 partly attach themselves directly to the outer surface of the rostellum. 
 By these muscles, the latter can be retracted to a variable extent, so 
 that the circular margin of the head becomes closed over it. The pro- 
 trusion is effected by means of the transverse muscles which constrict 
 the body, and in consequence drive what it encloses in the direction of 
 least resistance. In many cases there are special muscular arrange- 
 ments for the purpose, sometimes in the shape of well-developed pro- 
 tractors, which are stretched between the front of the head and the 
 rostellum, sometimes as muscles investing the rostellum laterally and 
 posteriorly, and developed in various ways. Thus, we find in the 
 Tcenia undulata of the thrush, &c., round the proper rostellum, a 
 second muscular sac, which extends nearly to the circle of hooks, thus 
 leaving the anterior end of the bulb free. By means of the longi- 
 
 FIG. 230. Rostellum of Tcenia undulata, after Niteche. ( x 100.) 
 
 tudinal and circular fibres of its walls, it is able to act powerfully 
 on the rostellum, and that all the more since the intermediate space 
 
 retractor muscles running inside the proboscis sheath of Echinorhynchus (see Vol. II.), 
 which deserve all the more notice since the four proboscides of Tetrarhynchus show exactly 
 the same arrangement of muscles. 
 
STRUCTURE AND ARRANGEMENT OF THE SUCKERS. 395 
 
 is filled with the same clear connective substance which we have 
 already observed inside the rostellum. 
 
 A similar arrangement is to be observed in the Cystotcenim 
 (Fig. 234), only that here the muscles both of the outer sac and 
 of the rostellum are considerably thickened at the expense of the 
 inner space. Eostellum and sac, therefore, appear as almost solid 
 muscular masses, whose true nature is all the more readily over- 
 looked, since, in their flattened character and external configuration, 
 they differ from the above described extended proboscis -like appar- 
 atus. We shall afterwards return to their discussion. 
 
 Like the rostellum, the suckers of the Taeniadae are organs which, 
 by the development of a homogeneous boundary sheath, are sharply dis- 
 tinguished from the surrounding body-parenchyma, and therefore 
 acquire a certain anatomical independence. All the four lie, of 
 course, at the same height, in the equatorial line where the head 
 is broadest, and are, in spite of their depth, usually entirely 
 buried in the substance of the head, so that only their borders project. 
 According to the height of these projections, the head appears 
 more or less quadrangular. The corners represent in position the 
 lateral borders of the body, and so far repeat even its flattened char- 
 acter, since the intervals separating the suckers are greatest where 
 
 FIG. 231. Apical surface and circle of hooks in Tcenia solium. ( x 80.) 
 
 they correspond to the surfaces of the body. We need hardly mention 
 that the suckers in the various species vary widely both in relative 
 and absolute size. The strength of the musculature differs also widely, 
 thus, of course, affecting the fixing power of the worms. The arrange- 
 ment of the fibres, however, is on the whole uniform throughout, as 
 was to be expected from the uniformity of the action performed. x 
 
 1 [Quite recently the structure of the suckers in the Taeniadse, as well as in other 
 groups of animals, has been made the subject of a special treatise : Niemiec, " Recherches 
 microscopiques sur les ventouses," Rec. zool. suisse, t. ii., p, i., 1885. R. L.] 
 
396 FAMILY 
 
 The main mass consists naturally of fibres, which increase and 
 diminish the internal cavity. The former are by far the most nume- 
 rous and powerful, and consist of radial fibres, which are usually 
 united into bundles and are stretched between the two surfaces of the 
 wall of the cup, and have their outer ends all directed towards the 
 centre of the strongly curved interior cavity (Fig. 234). As in 
 other situations, the fibres are embedded in a clear connective substance, 
 which is on the whole much degenerated, but here and there exhibits 
 distinct nucleated cells. The circular fibres counteract the radial, and 
 lie in groups among the former, preserving on the whole, though with 
 frequent deviations, an equatorial direction. On the border of the cup 
 they are developed into a regular sphincter, which is capable of being 
 greatly narrowed, and then protrudes almost like a diaphragm. At 
 the same time, the radial fibres of the border are also variable, inas- 
 much as they gradually change their former angle of insertion (90) 
 for one extremely acute. 
 
 Besides these muscles, there is usually present on the convex 
 outer surface a system of meridional fibres, which are much less 
 strongly developed than the others, but in the species with powerful 
 suckers sometimes form an exceedingly beautifully plexus. There are 
 also many other modifications, especially in the superficial muscula- 
 ture, which have not yet obtained close attention. 
 
 Change in the position of the suckers is, of course, 
 effected by those muscles which are attached to the 
 elastic envelope. They are fibrous bands which are 
 separated from the general body musculature, and 
 mostly belong to the longitudinal system. Some of 
 them run into direct attachment with the external wall 
 of the suckers, while others bend from their former 
 direction, and, crossing the fibres of the adjacent side, 
 enter it at a greater or less angle. In connection with 
 the quadruple number of the suckers, we have pre- 
 viously referred to the fact that the ventral and dorsal 
 surfaces in the Cestodes have but a comparatively 
 slight differentiation, and in the head especially are 
 scarcely distinguishable. These conditions are seldom 
 so pronounced in bilateral animals, but are charac- 
 FIG. 232. -- teristic of those animals which we are wont to oppose 
 
 Cephalic end of . , 
 
 a Tcenia canurus directly to them and to call Radiata. 
 with hexamerous jfc j s no ^ uninteresting in this connection to note 
 transverse section that the head of the Taeniadie sometimes exhibits a 
 of a sexually malformation which we not unfrequently find in radiate 
 
 mature joint. . * 
 
 ( x 25.) animals with tetramerous symmetry, viz., an increase of 
 
TRIANGULAR OR HEXAMEROUS T.ENLE. 397 
 
 radii to six. Such a head exhibits an increased number of hooks (in 
 T. co&nurus I have counted thirty-two, instead of twenty-eight), and 
 six suckers and longitudinal vessels, instead of the normal four. 
 Usually they are approximated in pairs, of which three are present. 
 The head, as a whole, has at the same time somewhat increased in 
 size. 
 
 But in such cases it is not only the head which is abnormal ; even 
 the jointed body of the worm has had a corresponding share in the 
 change. The neck shows, instead of ordinary flat shape, a triangular 
 form, and this passes by the growth and further development of the 
 proglottides into a structure which can hardly be otherwise described 
 than that of a double formation, and which, in its extreme forms, is in 
 principle entirely comparable with the double monsters which are 
 sometimes to be observed in man and in other animals. The parts 
 which, in the normal condition, are developed into the right and left 
 halves of a single body, become in such a case the outer halves of 
 two bodies which lie at an angle to one another, but have a single 
 interior half in common. The size and independence varies widely 
 in individual cases perhaps in connection with the disposition of 
 the superfluous suckers. 
 
 Even Bremser had noted these abnormalities as double monsters, 
 and had observed the connection between them and the presence of 
 six hooks. 1 Later observers (Klichenmeister and Leuckart) have 
 been able to do little more than confirm Bremser's report, which has 
 thus obtained general acceptance. Kiichenmeister will not consent to 
 regard them as abnormalities, but as a variety, since they are deter- 
 mined by what is really a " special law of development," and not " a 
 capricious deviation in development." 2 This is, however, illegitimate, 
 being founded on conceptions which have been long since rejected 
 in Teratology. Besides, from our present standpoint, there is no 
 fundamental distinction between abnormalities and varieties, and there- 
 fore the question as to the nature of these structures would be 
 quite irrelevant if Kiichenmeister had not also regarded the form 
 with tetramerous symmetry as a variety equivalent to that with 
 hexamerous. Quite apart from the fact that a species cannot possibly 
 consist of mere varieties different from one another, to place the two 
 forms on an equal platform is an unwarranted exaggeration, since the 
 hexamerous forms occur as a very small minority, perhaps only in 
 one case out of a hundred. 
 
 We find these six-rayed forms in many tape-worms, especially 
 among the Cystotcenice, which have indeed furnished us with 
 
 1 " Lebende Wurmer," &c., p. 107. 
 a " Parasiten," 2d ed., p. 145, note. 
 
398 FAMILY 
 
 almost all the instances. We shall afterwards return to these structures, 
 and will only now note that they have occasionally been described as 
 distinct species, as, for example, the Tcenia from the Cape of Good 
 Hope distinguished by Kiichenmeister, and the Tcenia lophosoma of 
 Cobbold. 
 
 Whether these malformations are hereditary, as Kiichenmeister 
 supposes, must remain undecided till it is settled experimentally. But 
 what we know of the occurrence of six-rayed bladder- worms is only in 
 favour of a spontaneous origin, since they are always found singly among 
 normal specimens which probably originated from the same brood. In 
 Ccenurus the six-rayed heads are found even on the same bladder as 
 the four-rayed, 1 as one may conclude from the fact that, after " feed- 
 ing" I found in a dog one six-rayed (or triangular) tape-worm but 
 one only among the numerous specimens with four suckers.- 
 
 Even the hooks sometimes undergo sundry malformations besides 
 the variations in number above referred to. These concern both the 
 root-like processes and the claws, and are sometimes so marked that, 
 instead of the proper hooks, only more or less irregular chitinous 
 knobs, in which one can at first glance hardly recognise the charac- 
 teristic and beautiful head armature. In the cases I have seen these 
 malformations mostly concern the whole circle of hooks, so that their 
 conditions must be sought rather in the common place of attachment 
 than in the individual papillae. Even a total abortion of the circle of 
 hooks has been observed. 
 
 The numerous abnormalities of the proglottides we shall have further 
 opportunity of studying. They are abundant enough, especially in 
 Tcenia saginata, but may be for the most part reduced to a sometimes 
 luxuriant, sometimes imperfect, or even wholly absorbed segmentation. 
 Occasionally one meets with tape-worms in which a second segment 
 is found laterally attached. The supernumerary segment is in such 
 cases usually partly abortive, though the contrary also occurs. Moniez 
 describes a case of Tcenia marginata which forked in two places, 3 
 
 1 This fact contradicts Moniez's supposition (Bull. Sci. dep. du Nord, p. 202, 1878) 
 that such a head might result from a twelve-hooked embryo, such as he had often observed 
 (see p. 330). 
 
 3 My experience of trianglar tape- worms is not exclusively limited to this one 
 case, but also includes two other cases of Tcenia sayinata. One of these, viz., Kiichen- 
 meister's T. capenais, I have formerly described (First German edition of this work, 
 Bd. i., p. 308). 
 
 3 " Observations teVatologiques chez les Tenias," loc. cit., p. 201. I may also mention 
 that Moniez has at different times observed that T. expansa, and once the T. denticulata 
 found along with it, were infested with Psorospermise. What Moniez has so designated is 
 not, however, in any way a Sporozoon (see p. 191), but a so-called Micrococcus (Panhisto- 
 phyton), and therefore a fungus, similar perhaps to those which I once found in Oxyuri* 
 see Vol. II.), and which Biitschli has also found in free-living Nematodes. Moniez also 
 reports finding his Psorospermiae in Echinorhynchus proteus. 
 
MALFORMATIONS OF THE PROGLOTTIDES. 399 
 
 thus producing each time two chains running side by side, which 
 were, however, so unequally developed that each supernumary chain 
 looked like a short lateral branch. Eecalling the 
 familiar fact that lizards, after losing their tails, not 
 unfrequently produce a double tail, it may perhaps be 
 presumed that the doubling is in the above case also 
 the result of an injury in which the chain had been lost 
 up to the proliferating neck. Perhaps it may even 
 happen, as is probably the case in the lizards just 
 mentioned, that the terminal portion gets torn longitudi- 
 nally, or in some other way irregularly injured. 
 
 In Tcenia ccenurus I have observed a remarkable 
 malformation which one may perhaps regard as a situs 
 inversus. The last eight to ten joints of the chain ex- 
 hibited perfectly normal sexual organs, but in inverted 
 position, inasmuch as the organs which should lie pos- 
 teriorly namely, the female reproductive organs 
 were situated anteriorly. The connection of this terminal FIG. 233. 
 chain with the anterior entirely normal portion was jomt^f^oS 
 effected by a short joint, with only testes and two peri- saginata ( x j). 
 pheral knobs lying opposite one another, which, in spite of their 
 resemblance to genital pores, had neither recognisable openings, nor 
 cirrhi, nor vasa deferentia. 
 
 Also it not unfrequently happens that in a series of quite normal 
 joints a segment is interpolated with only male organs. We have 
 already noticed some other deviations in the formation of the sexual 
 organs (p. 278). 
 
 Most zoologists include in the family Tseniadse only a single genus 
 Tcenia. This genus is, however, so rich in species we know almost 
 250 and these exhibit such striking and deep-seated divergences in 
 armature, sexual organs, form of the egg, and mode of development, 
 that we seem fully justified in splitting up the genus into a number 
 of smaller groups. This is not of course the place to enter specially 
 into the systematic arrangement of the Tseniadse, but we are 
 bound to give a rational treatment to the differences between the 
 various tape-worms infesting man, and that with reference to a 
 natural grouping of the genus. 
 
 The Tseniadse, then, we first divide into two groups (see p. 390), which 
 differ especially in the nature of their development. The first group in- 
 cludes the cystic tape- worms, which are distinguished from the others 
 by a great number of peculiarities, and exhibit developmental phases 
 formerly distinguished as Cystici. Not that the bladder-worm stage, as 
 
400 CYSTIC TAPE-WORMS. 
 
 such, belongs exclusively to this group ; on the contrary, the other 
 Taeniadae are also mostly bladder-worms in their youth, as has been 
 formerly noted in discussing their development. But the bladder- 
 worm stage of the latter represents a less perfect organization, not 
 only on account of its smaller size, but especially on account of the less 
 developed state of the embryonic caudal bladder. On these grounds, 
 therefore, there is some reason for distinguishing them from the true 
 Cystici, and we will in the meantime designate them " Cysticercoidei." 
 
 GROUP A. Cystic Tape- Worms (Cystici). 
 
 Tschudi, "Blasenwiirmer," Freiburg i. B., 1837. 
 
 Von Siebold, "Band- und Blasenwurmer :" Leipzig, 1854. 
 
 Leuckart, "Die Blasenwurmer und ihre Entwickelung:" Giessen, 1856. 
 
 Moniez, "Essai monogr. sur les Cystercerques," Trav. irutit. zod. Lille, t. iii : Paris, 1880. 
 
 These tape-worms are mostly of appreciable, and sometimes even of 
 considerable size. The head is very rarely unarmed, but is always 
 provided with a strongly muscular, lenticular, slightly projecting 
 rostellum, and a double, in some cases even triple, circle of hooks, which 
 decrease in size, and often change their form in the posterior rings. 
 Besides the claw, one can always distinguish two strong root-processes, 
 running one anteriorly,' 1 the other posteriorly, of which the latter is the 
 longer, especially in the anterior row. The proglottides, when ripe, are 
 of a longish oval form, and have a uterus whose longitudinal main stem 
 runs up the middle line, and in course of time develops a number of 
 more or less independent, generally much divided, lateral branches. The 
 vagina runs from the m'iddle of one side downwards in a curve to the end 
 of the uterus, and there comes into connection with the common duct 
 of the tvjo hand-shaped ovaries, and of the yolk-gland lying behind these. 
 The testes are numerous, and are diffused throughout the whole body. 
 The generative openings are found in irregular alternation on the right 
 and left sides. The cirrhus-pouch and seminal vesicle are of small size. 
 On the eggs one finds round about the embryo a firm shell of a brown 
 colour, and a more or less distinctly granular character, which is originally 
 surrounded by a second clear and distinct envelope. The embryonic 
 hooks are short and thin, and all the six are of uniform structure. 
 
 In both stages they live exclusively, so far as we know, in the Mam- 
 malia; as tape-worms, especially in Carnivora ; as bladder -worms, 
 especially in Rodentia and Euminantia. 
 
 1 [The reader is reminded that these words refer to the hook itself, not to the whole 
 Tcmia. W. E. H.] 
 
STRUCTURE OF THE ROSTELLUM. 
 
 401 
 
 In summing up these peculiarities we have referred to the structure 
 of the rostellum. It consists, as we mentioned, of a lenticular bulb, 
 which bears hooks, and effects their movement by its variable con- 
 tractility. The projecting circular ridge of the rostellum is situated in 
 the interspace between the root-processes, and brings these into 
 contact with the adjacent surface in such a way that the longer so- 
 called posterior processes lie on the anterior surface. The latter only 
 requires to change its radius of curvature to be able to act by means 
 of the processes on the position of the hooks. This change of form 
 occurs all the more easily and readily, since not only is the musculature 
 of the bulb specially strong, but the subjacent body-muscles come into 
 special relation to the latter. 
 
 Our knowledge of these arrangements is specially due to the in- 
 vestigations of Mtsche, 1 which were indeed primarily 
 concerned with Tcenia crassicollis, but which, according 
 to my observations, are also applicable to the other 
 tape-worms, at least to T. solium (of which Nitsche 
 was able to examine only one badly preserved specimen), 
 T. serrata, and T. cwnurus. Nitsche was, however, mis- 
 taken in regarding the bulb, which is the true rostellum, 
 as only an elastic cushion without proper contractility, 
 and only able to change its form and position by means 
 of the muscular apparatus which surrounds it as a shell. 
 The error involved in this conception is sufficiently 
 displayed when we compare Nitsche's " elastic cushion" 
 with the rostellum previously described in the case of 
 T. undulata, which only differs in this, that the bulb 
 and sac are much less muscular than in our cystic tape- 
 worms. To bring the structure of the latter into 
 harmony with the typical form, we only require to 
 suppose that the musculature has developed greatly 
 at the expense of the interior space, otherwise filled 
 with connective tissue, and has finally caused the cavity 
 to disappear. 
 
 Not much more remains to be said regarding the his- 
 tological structure of the rostellum. Under a sharply gitudinal se 
 
 T.CJ T i -i ft * O* * young T 
 
 denned porous and structureless external coat one finds serrata, consisting 
 a great number of fine fibres, which have a very regular ^ of ( h ^ a g ^ nd 
 course, and which fill up the whole mass of the bulb, 
 with the exception of a few, mostly separated, connective-tissue cells. 
 The arrangement of the fibres reminds one in many particulars of 
 that previously described in regard to the sac-like rostellum of the 
 
 1 Zeitschr.f. wiss. Zool. t Bd. xxxiii., p. 183 et seq., 1880. 
 20 
 
 FIG. 234. Lon- 
 section 
 
 cenia 
 
402 CYSTIC TAPE- WORMS. 
 
 Cysticercoids, but is more complicated, inasmuch as here we have 
 not only longitudinal and circular muscles, but also a system of radial 
 fibres which run from the middle point of the posterior surface dia- 
 gonally to the side-wall of the bulb (Fig. 234). The latter is further 
 ensheathed by a layer of circular muscles, which have been overlooked 
 by Nitsche, while those running longitudinally are stretched straight 
 between the two surfaces. In contraction these two surfaces would 
 be equally approximated were not the anterior one, 1 which is covered 
 only by the skin, more moveable than the posterior, and therefore 
 more obedient to the action of the muscles. In consequence of this, 
 when the longitudinal and circular muscles are contracted at once, the 
 bulb changes its quiescent form for that of a meniscus, which is open 
 towards the front, so that the hooks seated on the border assume an 
 almost vertical position. But besides the longitudinal muscles, the radial 
 muscles also exert a special force on the anterior surface of the bulb, 
 which arches forwards, and moves the hooks downwards in proportion 
 as the diameter of the posterior half narrows, and as the middle of the 
 posterior surface draws itself inwards in consequence of the funnel- 
 shaped arrangement of the fibres. 
 
 The operation of these radial fibres is further aided by the muscular 
 mass which lies behind the bulb, and which has been compared above 
 to the outer sac of the rostellum in Tcenia undulcda. This comes 
 into action at the same time and presses forward the posterior wall of 
 the bulb, which it surrounds as with a shell. This muscular mass 
 (see Fig. 234) consists of a whole series (six to nine) of discs laid down 
 one over the other, all of a meniscoid shape and surrounded by a com- 
 mon border, which is partly attached to the bulb itself, partly to the 
 subcuticula surrounding it, and is even connected by some of its 
 fibres with the lower roots of the posterior hooks, or rather with the 
 sacs in which they lie. The arrangement of the fibres is, as Nitsche 
 has shown, peculiarly complicated, for they bend in a bow-shaped 
 curve away from the periphery to the centre, and then out again to 
 the periphery, crossing one another in their course through the series 
 of layers. I cannot in any way grant a morphological independence 
 to this muscular mass, especially since its fibres come into frequent 
 connection with the surrounding musculature, and since posteriorly 
 they pass quite continuously into the ordinary muscles of the body. 
 
 We have already noted that the young stages of the cystic tape- 
 worms are characterised by the accumulation of a large quantity of a 
 watery fluid inside an embryonic bladder, which is penetrated by 
 numerous excretory vessels and muscular fibres. In Ecliinococcus the 
 presence of the muscular fibres has been denied, but they are never- 
 theless present, though in small numbers, and feebly developed. 
 
MECHANISM OF THE ROSTELLUM. 403 
 
 This is perhaps connected with the notable thickness and rigidity 
 of the cuticle, which would hardly permit of vigorous contraction. 
 The worm exhibits so many peculiarities, especially in the develop- 
 ment of its head, that we are bound to regard it as the type of 
 a special group of cystic worms. As we have mentioned above, the 
 occurrence of a special brood-capsule for the budding heads is very 
 characteristic, and perhaps also finds its explanation in the excessive 
 thickness of the cuticle. 
 
 Nor can we avoid noticing that, in regard to the cystic tape-worms, 
 an assertion has been lately made by Megnin 1 which throws doubt on 
 all we have been affirming as to the nature and development of these 
 animals, and even of all the Cestodes. According to his assertion, 
 the cystic tape-worms are in no wise independent forms, but represent 
 merely the heteromorphic condition of hookless tape-worms. The 
 latter, says Megnin, are the true typical Tcenice, which require for 
 their development neither change of host, nor cystic stage, but rather 
 result directly from the six-hooked embryos whenever these find 
 from the first conditions entirely favourable for their development. 
 In other cases the animals develop only circuitously through a 
 Cysticercoid stage, and may, according to circumstances, become a 
 cystic tape-worm, or return by metamorphosis to the typical form. 
 Thus, when the Echinococcus of a herbivore is transferred to the intes- 
 tine of a carnivore, it becomes Tcenia echinococcus, but it is developed 
 into T. perfoliata whenever the head, as sometimes happens, reaches the 
 digestive canal by perforation of the intestinal wall of the host. In 
 the same way Cyxticercus pisiformis develops in the dog to Tcenia 
 serrata ; but in the rabbit itself may become Tcenia pectinata. (!) 
 
 The two species here named are the only ones which Megnin 
 specially discusses, although he is of opinion that every hookless 
 Tcenia has its representative armed form. For any proof of this state- 
 ment one looks in vain. Our author has neither demonstrated the 
 asserted relationship by experiment, nor made it probable by the 
 existence of intermediate types. He has apparently no conception of 
 the extent of the positive observations on the development and struc- 
 ture of the Cestodes, which are quite enough in themselves to disprove 
 the conclusions which he has tried to establish on merely subjective 
 grounds and analogies. 2 
 
 1 Comptes rendus, t. Ixxxviii., p. 88, and in detail, Journ. anat. et physiol., t. xv., 
 p. 225, 1879. 
 
 2 The opinions and conclusions of Me'gnin on the Cestodes have been decidedly rejected, 
 not only by me (Archiv /. Naturgesch., Jahrg. xliii., Bd. i., p. 199,11877), but also by 
 Moniez (Bull sci. dep. Nord., p. 233, 1880). The latter is, indeed, as we have mentioned 
 (p. 280, note) so far in agreement with Me'gnin, since, according to his opinion, a great 
 many of the Tcenia undergo a continuous development within the same host. 
 
404 SUBGENUS CYSTOT^ENIA. 
 
 A. Cystic Tape- Worms in which the Head arises within the 
 Embryonic Madder. 
 
 Subgenus Cystotaenia, Leuckart. 
 
 We regard the cystic tape-worms in this division as normal forms, 
 and give them the first place in our consideration, not only because 
 they include the majority of the species, but particularly because in 
 their mode of development they closely follow the typical process of 
 the other tape- worms. To justify our assertion we may refer to what 
 we have already (p. 339 et seq.) said about the development of the 
 bladder- worms. What we have said will suffice also as an introduction 
 to these worms and their peculiarities, so far as they are revealed in the 
 young stages. Apart from the nature of the bladder and its usually 
 very lymphatic contents, the presence of the above described recep- 
 tacle is especially deserving of attention. It forms, as is well known, 
 a muscular pouch, which surrounds the rudimentary head with more 
 or less independence, and also subsequently encloses most of the body 
 of the worm which gradually originates between the head and the 
 bladder. 
 
 By the continuous growth of the former the receptacle becomes 
 ever larger with increasing age, but never loses its compact shape. 
 In consequence of this the worm inside draws 
 itself more tightly together 1 till the receptacle 
 can contain it no longer, and then it is gradually 
 protruded by the evagination of its basal portion. 
 This occurs most constantly and most strikingly 
 FIG. 235. Cysticercus in the Cysticercus fasciolaris from the liver of 
 
 celluloscB with the head i T 
 
 in the receptacle. ( x 2.) mice and rats, where the worm protrudes some- 
 times a finger's length from the bladder, and 
 becomes by solidification and segmentation so like an adult tape- 
 worm, that it has even lately been erroneously described as such 
 (Fig. 236). 
 
 To the subgenus Cystotcenia we refer not only the species with 
 the ordinary single-headed bladder-worm (Cysticercus), but also the 
 Tcenia ccenurus, which, in its youthful state, is well known to be poly- 
 cephalous. This proceeding is amply justified by the development 
 and subsequent condition of the head. The resemblance between 
 Ccenurus and Echinococcus is only superficial, and by no means war- 
 
 1 The opacity caused by the twistings of the body of the worm within the receptacle 
 aggravates the difficulty of investigation to such an extent that the earlier, and sometimes 
 even the modern (as in Davaine's work), descriptions and illustrations of the parts of 
 bladder in situ are with few exceptions useless. 
 
NUMBER AND DISTRIBUTION OF THE SPECIES. 
 
 405 
 
 FIG. 236. 
 Cysticercus 
 fasciolaris 
 (nat. size). 
 
 rants the union of the two species, though this has been frequently 
 proposed by certain helminthologists. x 
 
 The number of species of tape-worm belonging to this 
 group is, as far as we yet know, at most a dozen and a half. 
 Of course we are as yet hardly acquainted with any but 
 European species, and these but imperfectly, so that in course 
 of time the number will probably be much increased. 2 
 With the exception of the Tcenia solium e Cyst, celluloses 
 and the T. saginata e Cyst, bovis, they are all found in 
 Carnivora ; in the cat, T. crassicollis e Cyst, fasciolari ; 
 in the dog, T.serrata e Cyst.pisiformi, T.marginatas Cyst, 
 tenuicolli, T. Krabbei e Cyst, tarandi, T. ccenurus e Ccenuro 
 cerebrali; in the fox, T. crassiceps e Cyst, longicolli, 3 T. 
 polyacantha e Cyst. sp. ; in the polecat, T. intermedia, T. 
 tenuicollis e Cyst, talpce, &c. 
 
 The size of tape-worm body differs widely in the 
 individual species, but is on the whole very considerable. 
 The hooks also are always large and strong, except in a 
 few species, such as the small T. tenuicollis, and indeed 
 few other Tcenice can equal these forms in this respect. 
 The anterior root of the smaller hooks is broadened at the end and 
 notched like an inverted heart. 
 
 In spite of much structural resemblance, the different species are 
 not hard to distinguish from one another. It is true that one of our 
 most famous helminthologists v. Siebold affirmed the opposite only 
 a few decades ago, and declared emphatically that the Tcenia solium 
 of man was identical with the above-mentioned tape-worms of the 
 dog, and also with T. crassiceps and T. intermedia. This has, however, 
 been sufficiently disproved by Klichenmeister and by myself. Even 
 if we regard the differences in size and habit as irrelevant in spite of 
 their constancy, and due, as v. Siebold would have it, to the differences 
 in the hosts inhabited, there are yet other weighty and distinctive 
 
 1 Zeder unites these two to form the genus Polycephalus. 
 
 2 In the liver of A rctomys Ludoviciana I observed just lately the Cysticercus of a hitherto 
 unknown Tcenia, with twenty-four extremely small hooks. Moniez has also enriched 
 our knowledge of the bladder-worms by the discovery of a new species, Cysticercus Krabbei. 
 It lives in the muscles of the reindeer, and is developed in the dog to a segmented chain 
 (loc. cit., p. 44). 
 
 3 The doubt which Moniez casts (loc. cit., p. 69) on the relationship between Cysticercus 
 longicollis and T. crassiceps is quite gratuitous. I have associated the two forms not only 
 because of the hooks, but because I have produced the Tcenia in question from the Cysti- 
 cercus. It is impossible to confuse the latter with the Cysticercus talpce (which, though 
 hookless, according to Rudolphi, is in reality provided with small hooks), although both 
 species occur both in the mole and in the field-mouse, and although the former also has 
 sometimes been designated Cysticercus talpce. It is equally impossible to regard 
 Cysticercus longicollis with Dujardin as a young Cysticercus fasciolaris. 
 
406 SUBGENUS CYSTOT^ENIA T^ENIA SAGINATA. 
 
 peculiarities. This is above all true of the hooks, whose form, size, 
 and number, though variable to a certain extent, are so characteristic 
 of the different species, that on them alone one can, after some practice, 
 establish a diagnosis. Not less distinctive are the differences in the 
 anatomical structure, especially of the generative organs, and in the 
 development, as we shall afterwards see, in the case of the forms which 
 specially interest us. But granted that it were possible to explain 
 all the differences between Cysticercus celluloses and C. tenuicollis or 
 Coenuriis,OT those between Tcenia solium and T. marginata or T.canurus, 
 on the theory of the variability of species a theory which might with 
 equal justice be considered as overturning all systematic zoology yet 
 one fact alone is enough to forbid the identification of the two forms. 
 This fact is the result of experiment. The attempt to give a sheep 
 staggers with eggs of T. solium or T. serrata yields no result, but 
 after administering the ripe proglottides of T. cosnurus, we are not 
 only sure of the result, but can predict the date of the appearance of 
 the first symptoms with almost mathematical precision. By the oft- 
 repeated experiments of Haubner, Baillet, myself, and others, it has 
 been indisputably shown that certain bladder-worms always result 
 from certain eggs, and pass into definite tape-worm forms. Besides, 
 when one occasionally finds all the three tape-worms of the dog in the 
 same intestine without any loss of their characteristic peculiarities, 
 one can hardly persist in regarding them as mere varieties, owing 
 their special form directly to the circumstances of their life. 
 
 a. Cystic Tape-worms without Circlet of Hooks. 
 (Taeniarhynchus, Weinland.) 
 
 Taenia saginata, Goze. 
 
 (Taenia solium, Auct. p. p., Taenia lata, Auct. p. p., Taenia dentata, Batsch, 
 Taenia mediocanellata, Kuchenmeister. ) 
 
 Goze, " Eingeweidewurmer, &c.," p. 269 (T. cucurbitina, grandis, saginata). 
 
 Kuchenmeister, "Cestoden, &c.," p. 107, tab. ii., 1853 (T. mediocanellata). 
 
 Idem, "Parasiten," first German edition, p. 88 ; second edition, p. 140 (T. media- 
 
 canellata). 
 Leuckart, "Parasiten," first German edition, Bd. i., p. 258 (T. mediocaneUata). 
 
 This is the largest of the human Taeniae, and when extended measures 
 7 or 8 metres, but in its contracted state is only about 4 metres long ; 
 it is composed of from 1200 to 1300 segments, of which more than three- 
 fourths belong to the anterior half of tlu body. But it is not its length 
 alone that characterises this worm ; it is also of unusual breadth and 
 thickness, and is provided with segments which arc remarkable for their 
 
DEFINITION OF MNIA SAGINATA. 
 
 407 
 
 size and firm appearance. Especially characteristic is the breadth 
 of the middle segments, which amounts to 12 or 14 mm. The neck 
 seldom measures less than 1 to 1'5 mm. 
 Since the length of the segments increases 
 comparatively slowly, the great majority 
 are broader (sometimes three or four 
 times broader) than they are long; only 
 the ripe proglottides containing embryos 
 are (even in their contracted condition) 
 of the well-known melon-seed shape. The 
 large hookless head (1/5 to 2 mm.) has a 
 flattened crown, with a pit-like hollow in 
 the middle, and has four large and very 
 powerful suckers, which, however, usually 
 project only slightly, and are frequently 
 surrounded by a black, more or less broad, 
 pigmented border. In the mature proglot- 
 tides the same pigment is often found in 
 the vagina, vas deferens, and testes. The 
 complete development of the germ-producing 
 organs takes place at about the 600th 
 segment, while the embryos only attain ma- 
 turity 360 or 400 joints further on. The 
 number of the so-called " ripe " segments 
 may be estimated at from 150 to 200. The 
 eggs have a thick shell, with a border of little 
 rods. They are generally markedly oval, 
 and almost always provided with the prim- 
 ordial yolk-skin. The uterus which encloses 
 them is characterised by the large number 
 (twenty to Jhirty) of its lateral branches, 
 which run out close beside each other, and 
 exhibit many dichotomous divisions. The 
 greatly projecting porus genitalis lies in the 
 ripe proglottides on the lateral margin, at 
 a perceptible distance behind the middle. 
 If, as often happens, the joints have been spontaneously liberated, they are 
 generally found without eggs and shrivelled up, but still of considerable 
 size and thickness. Before the evacuation of the eggs they generally 
 measure from 18 to 20 mm. in length and from 5 to 7 mm. in breadth. 
 The new formation and growth of segments take place so quickly, that 
 about eight, or even more, proglottides are separated daily, even when, as 
 is the ride, only a single worm is present. 
 
 FIG. 237. Tcenia saginata 
 (natural size). 
 
408 
 
 HISTORICAL ACCOUNT OF T^NIA SAGINATA. 
 
 The bladder-worm generally inhabits singly the muscles of the ox, but 
 is occasionally found in the internal organs. It contains only a small 
 quantity of fluid, is of a roundish form, and hardly ever attains the size 
 of 1 cm. 
 
 FIG. 238. Fio. 239. 
 
 B 
 
 FIG. 238. Head of Tcenia taginata in 
 contracted (A) and extended condition 
 (B). (x 8.) 
 
 Fio. 239. Ripe segment of T. saginata. ( x 2.) 
 
 Historical Development of our knowledge of Ttenia saginata and 
 the related Forms. 
 
 We give Tcenia saginata (T. mcdiocanellata, Klichenmeister) the 
 first place in our description, partly because it is the only cystic tape- 
 worm with unarmed head which occurs in man, and partly also from 
 historic reasons ; for, in opposition to the widely spread belief that 
 the so-called Tcenia mediocanellata was only discovered a few 
 decades ago, a critical analysis of the existing information regarding 
 the human tape-worms shows it to be the very species that has been 
 longest known. For not only does the oldest complete picture of a 
 human Tcenia (that of Andry) unmistakeably represent Tcenia 
 saginata, but it is further quite indubitable that the e\//,iV#e? 
 TrXaretat, and also the identical rawiai, (or Krjptai) of the Greeks the 
 Lumbrici lati and Tcenice of the translators and commentators refer 
 especially to this species, and by no means to the T. solium of Kudolphi. 
 
 The descriptions of the ancients, it is true, do not supply any direct 
 foundation for specific diagnosis. They are so unsatisfactory that in 
 their time they did not even suffice to establish the animal nature of 
 
TAPE- WORMS KNOWN TO THE ANCIENTS. 409 
 
 the tape-worm. Even in the sixth and seventh centuries after Christ, 
 Aetius and Paulus ^Egineta explained the tape-worm as a meta- 
 morphic product of the intestinal mucous membrane, 1 and in later 
 authors one frequently meets with similar views. But there are not 
 wanting positive proofs of our statements. First I would note that 
 Tcenia saginata is much more frequent in the countries round the 
 Mediterranean, and especially in the East, than T. solium, which belongs 
 more to the north of Europe. So, too, the statement of Hippocrates, 
 that the tape-worm patient very often evacuates "quali quid cucumeris 
 semen " (olov GIKVQV crTrepfjua) that is to say, that he voids in portions 
 the ripe joints of the worm, or proglottides describes a phenomenon 
 which is much more frequent and much more striking in the case 
 of Tcenia saginata than of Tcenia solium. 
 
 I will not, however, assert that it was exclusively Tcenia saginata 
 that was known to the Greek physicians. I can the less do this, since 
 T. solium is by no means absent from the East, as is decidedly proved 
 by the fact that the bladder-worm of the pig, from which it is de- 
 scended, has been known there from antiquity. The only question is, 
 what particular form it was with which the physicians of antiquity 
 and of later times were most familiar, and to which their statements 
 mostly refer ? And that form is, as we have said, decidedly T. saginata. 
 When T. solium occasionally occurred, there would seem to the older 
 physicians all the less reason to mention it specially, and to distin- 
 guish it from the larger and more frequent, or at least more striking 
 forms, since it is by no means very markedly different from T. saginata. 
 
 The Arabian physicians and their immediate successors must also 
 have made their investigations mainly on Tcenia saginata. This may 
 be inferred not only from the geographical distribution of the two 
 worms, but because, like Hippocrates, they regarded the exit of the 
 so-called Vermes cucurbitini (Chabb-al-Kar'i) as proof of the presence 
 of the tape-worm, and were even many of them of the opinion that the 
 latter only originated subsequently from the former by the forma- 
 tion of a chain. 
 
 At any rate, the exit of the tape-worms, which seemed to the 
 ancients so characteristic, excluded the supposition that their Lumbricus 
 latus is the same as the present Bothriocephalus latus, which, instead 
 of separate joints, usually gives them off only in numbers. And 
 since the latter is almost absent from the countries in the Mediter- 
 ranean basin, and if found in the south and south-east of Europe, is 
 usually confined to Switzerland, and the districts in its immediate 
 
 1 "Lumbricus latus transmutatio, ut ita dicam, est membranse intestinis intrinsecus 
 agnatae in corpus quoddam animatum." Aetius, "Medicina tetrabiblos " iii., serin, i., 
 cap. xl., de lurnbrico lato. 
 
410 HISTORICAL ACCOUNT OF T^ENIA SAGINATA. 
 
 neighbourhood, it is very probable that it was quite unknown to the 
 earliest physicians and naturalists. Certainly it did not enter into the 
 minds of the first observers of Bothriocephalus Thaddaeus Dunus, in 
 Locarno (1592), and Gaspard Wolphius in Zurich to identify their 
 worm 1 with the tape-worm of the ancients; although, after all, that 
 proves nothing more than that the specific knowledge of the parasites 
 was at that time extremely meagre and superficial. If they had had 
 opportunity to compare their worm with the genuine Tcenia, the 
 difference between the two parasites would not have escaped their 
 notice any more than it escaped that of the clinical physician, Felix 
 Plater of Basle, who, in his famous " Opus praxeos medicae" (1602), 
 mentions them for the first time as two different human tape-worms. 
 Plater's description is so expressive of the characteristics of this worm, 
 and of the then prevailing views, that I cannot refrain from quoting 
 it here. " Per podicem," say s Plater, 2 " corpora . . raro ejiciuutur 
 diversorum generum, e quibus unurn fasciam quandam refert mem- 
 braneam, intestinorum tenuium substantive similem, eorum longi- 
 tudinem adaequantem, minime tamen, uti ilia, cavam, sed digitum 
 trans versum latam, quam latum Lumbricum appellant, rectius Taeniam 
 intestinorum, siquidem cum Lumbrico nullani habeat siinilitudinem, 
 nee uti Lumbricus vivat aut loco moveatur, sed tamdiu, donee nunc 
 integrum, magno impetu aut terrore patientis existimantis intestina 
 omnia sic procedere, vel abruptum elabatur. In qua fascia plerumque 
 linese nigrae transversae, spatio digiti ab invicern distantes, per totam 
 ipsius longitudinem, et ad formam vertebrarum in intervallis illis 
 extuberantes apparent. . . . Alias vero aliter formata ejusmodi taenia 
 longissima, veluti ex portionibus multis cohrerentibus et quae ab 
 invicem abscedere possunt constare videtur, quas portiones, quum 
 cucurbits semina quadrata nonnihil referant, cucurbitinum vermem 
 vocant. Qualis rarius integer, sed plerumque in plura frusta divisus 
 rejicitur; qua singula privates vermes esse, cucurbitinos dictos, 
 crediderunt, licet tantum fasciae illius abrupta sint particula." 
 
 A century passed without Plater's statements receiving any impor- 
 tant addition or correction. The two species of tape-worm which lie 
 established were pretty generally accepted, and were usually called the 
 " species prima et secunda Plateri," but our knowledge of them was 
 hardly at all advanced till Andry published his investigations. 3 Like 
 
 1 That it was a Bothriocephalus that these physicians observed, can of course only be 
 inferred, but with some probability, from their statements. Thaddaeus, for example, 
 ("Miscell. med.," cap. v.) describes the worm as "squamosus, instar serpentis, nisi 
 rectius geniculatus," which could scarcely apply to T&nice. 
 
 2 Loc. cit., t. ii. , "De anim. excretion." 
 
 z " De la generation des vers dans le corps de 1'homme " p. 51 ct scq. : Amster- 
 dam, 1701 (Reprint). 
 
ETYMOLOGY OF THE WORD " SOLIUM." 411 
 
 Plater, he also speaks of two species of the genus Tcenia " L'un, qui 
 retient le nom du genre et qui s'appelle proprement Tcenia, lequel n'a 
 point du mouvement ni de tete forme'e; et Fautre, qui se nomme 
 Solium, a parce qu'il est toujours seul de son e"spece dans les corps, 
 ou il se trouve, et qui a du mouvement et une tete ronde fort bien 
 formee, faite comme un poireau." 
 
 This is not the first time that we meet with the name Solium. 
 Even earlier observers used it, the earliest, so far as is known, 
 being Arnoldus de Villanova, who, in 1300, reports of a Lumlricus, 
 " qui aliquando emittitur longior uno vel duobus brachiis, qui Solium 
 sive Cingulum dicitur." Villanova had, therefore, found the name 
 somewhere else. Its origin is uncertain, for the derivation from solus 
 suggested by Andry is grammatically incorrect (on account of the i), 
 and is as obviously made to suit the case as is also the derivation 
 from solium, a throne a word which suggests the solitary occurrence 
 of the tape -worm (Tcenia saginata), a fact of which we find a hint 
 even in Hippocrates. The hook-bearing T. solium often occurs in 
 groups. 
 
 In order to ascertain so far as possible the etymology of this 
 strange appellation, I sought to interest my honoured friend and 
 colleague Dr. Krehl, Professor of the Oriental Languages at Leipzig, in 
 the question, and, to my great joy, have received from him the follow- 
 ing explanation : 
 
 " It is impossible," writes Krehl, " to derive the word Solium from 
 the classic languages, and we are further directed towards the Oriental 
 tongues by the fact that both in Arnoldus, who translated several 
 works of Avicenna, and in his predecessors, a knowledge of them may 
 be assumed. One naturally thinks first of Arabic ; but none of the 
 words by which the Arabs designated the tape-worm for example 
 cldd (worms), or chabb-al-kar'i . (properly gourd-seed) agrees in sound 
 with the word Solium. 
 
 " But as the Jews in the East and in Spain frequently busied them- 
 selves with the practice of medicine, or, more generally, with medical 
 studies, Hebrew might be referred to ; but with its 'kdkejdnin or kirsa 
 or dtire^. perhaps ddde\ it supplies nothing that might serve as an 
 explanation of the word Solium. Under these circumstances I should 
 like to offer as an explanation the certainly somewhat remote Syriac 
 word for the tape-worm, namely, schuschl-e (properly " chains "), which 
 is sufficiently attested by Bar Bahlul (see Payne-Smith, " Thesaurus 
 linguge Syriacse," i., 317, infr. s. v. Askdrides), and by Ferrari 
 (" Nomenclator Syriacus," p. 651). 
 
 " Medical science had reached a high development in Syria, and 
 the Arabians doubtless first received from the Syrians an exact know- 
 
412 HISTORICAL ACCOUNT OF MNIA SAGINATA. 
 
 ledge of the writings of the Greek physicians, and of the natural 
 sciences. In this way the word would come to be used with its special 
 meaning 1 by the Arabians, and through them by the French or Spanish 
 authors of the Middle Ages. The phonetic transition from the 
 original schuschl-e (e is only the plural termination) to sol-ium might 
 be thus explained. Among the Arabians it would be changed into 
 susl or sosl, and among the romance authors it would lose the second s, 
 first in pronunciation, and then in writing, just as the disappear- 
 ance of the s before the consonant can be proved in meme (for mesme), 
 He (for isle)', maitre (for maistre), &c. Sylvius says in his " Isagoge" 
 " S ante t et alias quasdam consonantes in media dictione (that is to 
 say, in the middle consonant) raro ad plenum, sed tantum tenuiter 
 sonamus et pronunciando vel elidimus vel obscuramus." 
 
 We shall now, however, turn from this etymological excursus, 
 which has given us a thoroughly satisfactory explanation of a for- 
 merly almost meaningless appellation. 
 
 The above-mentioned statements of Andry are all the more 
 important in connection with our subject, since they are accompanied 
 by drawings and descriptions which leave not the slightest doubt 
 regarding the nature of the Tcenia or of the Solium. The " Tcenia " 
 turns out to be the present Bothriocephalus, with its uterine-coils, 
 which were regarded as vertebrae (hence Tcenia a e*pine), and the 
 Solium " (T. sans e'pine) turns to be a large-jointed Tcenia; not, 
 however, the Tcenia solium of later and modern helminthologists, 
 but quite undeniably, as has already been mentioned, Kiichen- 
 meister's Tcenia mediocandlata, with its firm joints and large black 
 head 2 (somewhat too large in the picture). As to the idea that the 
 four suckers were eyes, and that the uterine coils were vertebrae, we 
 will pardon its naivete, and by no means judge it so harshly as other 
 investigators have sometimes done. The designation, " Ver solitaire," 
 which Andry uses for his Solium, also suits Tcenia saginata, and was 
 but little objected to until men acquired a more accurate knowledge 
 of Tcenia solium, Rud., which often occurs in numbers. 
 
 Andry was, however, not the only investigator of that time who 
 described the modern Tcenia saginata as Solium, as is shown, for 
 instance, by the pictures in Vallisnieri's treatise, " De vermium 
 humani corporis." These figures undoubtedly represent the charac- 
 teristic peculiarities of the former worm. 
 
 1 It may be pointed out in this connection that even at the present day the tape -worm 
 (Tcenia saginata) is extremely prevalent in Syria. See M6m. acad. Md. Paris, p. 998, 
 1877. 
 
 a " Ce ver a la tete noire, plate, un peu arrondi, ou sont quatre ouvertures, deux d'un 
 c6te" et deux autres au c6te oppose", " loc. cit. This shows how incorrect is the assertion of 
 Kiichenmeister (" Parasiten," 2d ed., p. 141, note), that Andry saw no head in his Tawia. 
 
THE T.ENIA LATA OF BONNET. 413 
 
 But an exact and detailed description of the worm was still 
 lacking. Only after the course of half a century was this want 
 apparently supplied by a treatise of the famous Genevan natural 
 philosopher Bonnet, " Sur le ver nomme' en latin Tsenia, en francos 
 Solitaire." * 
 
 The description given by Bonnet in this work of the head of the 
 particular tape-worm, which he observed, agrees in all essential points 
 with that of Andry. It is true that he only succeeded in finding it 
 once with certainty, but in this case it appeared distinctly, just as 
 Andry described it, as a small black knob, which was placed on a 
 thin neck, and consisted chiefly of four plugs arranged in pairs and 
 with only one terminal opening. The surface (apex) lying between the 
 suctorial plugs, which, in the other tape- worms (as especially shown 
 by Tyson in the four from the cat) 2 is provided with circles of 
 hooks, in this case exhibited nothing but a shallow depression (un 
 enfoncement). 
 
 But in spite of this conformity there was a great and striking 
 difference between the two descriptions ; for, from the structure of their 
 joints, Bonnet's tape- worms belonged, not to the first but to the second 
 species of Andry and Plater, or, in other words, they were not Tcenice, 
 but Bothriocephali. 
 
 Since Bonnet made his worm the subject of thorough investigation, 
 and supplied the first really correct figure of it, at Geneva, where 
 Bothriocephalus was very frequent, and where he had abundant oppor- 
 tunity of observing the parasite, it was easy to suppose that the head 
 structure, first observed by Andry in the tape-worms, occurred in the 
 " Tcenici " ( = Bothriocephalus, Eud.) and also in the " Solium " (the 
 modern Tcenia saginata) assuming of course that the description of 
 Andry was based on no oversight or error. 
 
 And indeed this supposition long obtained favour, and was not 
 refuted until thirty-seven years later. A mistake had, indeed, been 
 made not, however, by Andry but by Bonnet. The worm whose 
 head Bonnet described really represents a Tcenia saginata (Solium 
 of Andry), but the joints mentioned in connection with it originated 
 from the modem Bothriocephalus. 
 
 Possibly the confusion arose from the circumstance that Bonnet, 
 
 1 Mem. de Maihematique et de Physique pres. a VAcad. roy. Paris, t. i., p. 495, 1750. 
 
 2 With the exception of the statements of Tyson and Andry, any account found in 
 ancient literature of the head-formation of the tape-worms is based on gross errors and 
 fantastic misrepresentations, which may here be omitted. I refer any one who is interested 
 in these to Tyson, " Lumbricus latus," Phil. Trans., vol. xii., No. 146, p. 124, 1683, 
 and to the compilation of Werner, "Vermium intest. br. exposit." tab. iv. : Lipsiae, 
 1782. Even in the year 1762 Linne* also flatly denies the existence of a head in the 
 tape- worms (" Amcenitates Acad.," tab. ii., p. 66). 
 
414 HISTORICAL ACCOUNT OF T^NIA SAGINATA. 
 
 who had no opportunity of observing any other tape-worm than 
 Bothriocephalus, and who believed that there was no other species in 
 Geneva, had, when examining his Tcenia saginata, only found a com- 
 paratively short chain of joints at his disposal, and the shortness of 
 the anterior joints, which is so characteristic of this species, would all 
 the more easily lead him astray, since he was inclined to base his 
 specific distinctions principally upon the form of the joints, as may 
 be seen from the fact that he named the modern Bothriocephalus (re- 
 garded by him as the Lumbricus latus of the ancients) " Tcenia a 
 anneaux courts," in contradistinction to Tcenia, which he calls " Tcenia 
 a anneaux longs." 
 
 Although Bonnet himself recognised his mistake, 1 and exposed 
 the delusion under which he had been labouring, by discovering the real 
 head of his Tcenia lata (Bothriocephalus), and demonstrating its wholly 
 different structure, yet the false idea which he originated has been 
 of most fatal influence in the history of Tcenia saginata. 
 
 Bonnet's second work was less circulated, and the corrections 
 were almost completely overlooked, and thus it happened that a worm 
 called Tcenia lata was known in helminthological literature until the 
 time of Bremser (1819), who appreciated 2 Bonnet's later observations, 
 and also recognised a species of Eudolphi's genus Bothriocephalus in 
 Bonnet's worm. This so-called Tcenia lata was said to be charac- 
 terised by short joints, a median generative opening and coiled 
 uterus (d corps en manibre de fleurs), associated with a hookless head 
 with four suctorial pits a species, indeed, which does not occur at all 
 in nature. 3 
 
 Nor was it only a few or the more inexperienced who adhered to 
 this error, but the greatest helminthologists of the time, headed by 
 Pallas, 4 and including Goze, 6 Bloch, 8 and Eudolphi. 7 None of them 
 had any hesitation in recognising Tcenia lata as a fully justified species, 
 without, however, being able in any way to confirm Bonnet's state- 
 ments on the ground of their own investigations. 
 
 1 " Nouvelles recherches sur la structure du Teenia," Observed, sur la Physique, <kc., 
 p. 243, Paris, 1777. 
 
 2 " Lebende Wiiriner," &c., p. 92. 
 
 3 That the real Tcenia saginata is sometimes designated by the name Tcenia lata, in- 
 stead of this fictitious animal, is shown by the fact that in the Giessen Zoological Museum, 
 lately incorporated with v. Sominering's collection of Helminths, there was a T. saginata, 
 to which this name was affixed, while the Tcenice (with hooks) were correctly named T. 
 solium. 
 
 4 "Bemerkungen iiber die Bandwurmer in Menschen und Thieren," Neue nordische 
 Beitrage, i., p. 64, 1781. 
 
 6 " Versuch einer Naturgesh.," &c., p. 298, 1782. 
 
 6 " Abhandlung von der Erzeugung der Eingeweidewiirmer," p. 17 : Berlin, 1782. 
 
 7 " Entozoor. hist, natur.," vol. ii., p. 70, 1810. 
 
THE TJESIJE OF LINNE AND PALLAS. 415 
 
 Besides this Tcenia lata, however, there figured among the human 
 tape- worms a second species with short joints and median openings. 
 This form was first advanced by Linne as Tcenia vulgaris, 1 and was 
 said to be distinguished from Tcenia lata by its less broad body, and 
 by its exhibiting two openings, one behind another, on the more ex- 
 tended joints, while Tcenia lata had only one. Pallas, who, notwith- 
 standing his knowledge of Bonnet's second treatise, firmly believed 
 that Tcenia lata was provided with four suctorial pits, thought that 
 this T. vulgaris alone was furnished with the Bothriocephalus-liQa.d, 
 and expressed the doubt whether what Bonnet had described as " a 
 somewhat inflated delicate point, cleft longitudinally, but without 
 papillae or circlet of hooks," was really the head, and whether it might 
 not be simply " the snapped end of the chain." Eudolphi, however, 
 recognised neither this second short-jointed species, nor T. tenella, 
 another form distinguished by Pallas, but classed them both with T. 
 lata a proceeding which was afterwards followed by the majority of 
 investigators, and especially by Bremser. 
 
 These short-jointed human tape- worms with median pores were 
 thus contrasted with the long-jointed forms, with laterally situated 
 " osculum," which from this time were, after the example of Linne, 
 generally (and always in our century) called Tcenia solium. Pallas 
 indeed departed from this rule by exchanging Linne's name for that 
 of T. cucurbitina, a name which seemed in some measure justified, 
 since he (Pallas) comprehended under it not only the long-jointed 
 human tape-worms, but, further, the related forms in dogs and cats, 
 which we now rightly regard as separate species. Among other 
 characters, they were all credited with a cephalic armature, as had 
 had meanwhile been repeatedly demonstrated by Tyson on the apex 
 of tape-worms infesting mammals. 
 
 Linne had, moreover, already noted the circumstance that Tcenia 
 solium did not always exhibit exactly the same appearance in man. 
 After having described the typical form (Tcenia saginata), with refer- 
 ences to Andry, Vallisnieri, and others, he continues 2 as follows : 
 " In hominibus ssepius hie ipse vermis maxime planus, macilentus et 
 fere membranaceus ejicitur, instar vittae, quod ex eo forte est, quum 
 raro nisi mortuus ex homine expulsus obtineatur, et sic mortuus 
 spiritu vini committitur, ut fibras suas ab irritatione spiritus contra- 
 here nequeat, quemadmodum fit in vivo verme spiritui indito." It is 
 further added that specimens in this condition somewhat resemble 
 Tcenia vulgaris. 
 
 The same fact was also noted by several of the later investigators, 
 
 1 " Amcenitates academics," vol. ii., p. 69 : Holmiae, 1762. 
 
 2 Loc. cit., p. 69. 
 
416 HISTORICAL ACCOUNT OF T^ENIA SAGINATA. 
 
 but these differed from Linne*, in so far as they did not ascribe the 
 difference in the appearance and nature of the worms to any subse- 
 quent modification, but regarded it as original and present from the 
 first. Thus Pallas 1 informs us that when Tcenia cucurbitina occurs 
 in dogs and wolves, it is often, in spite of perfect similarity in the 
 form and proportions of the joints, considerably smaller than in man. 
 And in regard to its occurrence in man, he adds, " that from reasons 
 which do not seem exactly to harmonise with the apparent constitution 
 of the host, and which are difficult to explain, it is sometimes deli- 
 cate, thin, and slender, and at other times very large, thick, and as it 
 were fattened," as he is able to prove " by remarkable examples " 
 which he had expelled " from a thin and sickly girl between her 
 twelfth and fifteenth year." In the largest and ripest joints, he says 
 that the difference is sometimes in the proportion of one to three, for 
 in the smaller animals the length and breadth of these joints is hardly 
 four lines by two, while in the larger ones it is more than eight by 
 five. If several tape-worms be voided, they are usually of about the 
 same size and of similar form and joints, for he knows no instance of 
 several " species " having been observed together in the same man. 
 
 The foregoing descriptions, and the reference to Andry, thus 
 enable us to recognise in these large and thick worms our Tcenia 
 saginata, while the smaller and thinner ones are the present T. solium, 
 which, except in the suggestions of Linne* above-mentioned, is here 
 distinctly described for the first time. 
 
 Goze declares himself still more definitely, and divides Tcenia 
 cucurbitina which is here, however, exclusively confined to the 
 human tape-worms into two groups. 2 The former of these is "the 
 familiar large one, with long, thick, flattened joints," and is named by 
 him Tcenia cucurbitina grandis saginata; while the latter, "which 
 seems to be a variety of it, but continues to be the same under all cir- 
 cumstances," is designated T. cucurbitina plana pellucida. It is true 
 that the heads are said to be provided in both groups with a circlet of 
 hooks, but from the description and drawing it is evident that this 
 supposition is based upon a mistake, for the first familiar form 
 (Goze recommends Andry's figure, except the head, as pretty good) 
 is evidently the unarmed T. solium of the older investigators. The 
 second form, although less common elsewhere, is, according to Goze, 
 the most frequent of the two around the Hartz. 
 
 Batsch agrees with this idea of Goze, 3 except that under the name 
 T. cucurbitina which he prefers to the " quite unsuitable " name T. 
 
 1 Loc. cit., p. 47. 
 
 2 Loc. cit., p. 278. 
 
 3 " Naturgeschichte der Bandwurmgattung," p. 121 : Halle, 1786. 
 
GOZE'S TWO VARIETIES OF TAPE-WORM. 417 
 
 solium he mentions, after Pallas' example, besides the "large and 
 strong " and the " flat, delicate, and transparent " varieties, a third 
 one, namely, " the cucumber tape-worm of the dog " (T. serrata, Paid.), 
 which " ought not to be omitted, if the other two are explained as 
 mere varieties." The differences between these forms, and especially 
 between the first two, are, he tells us, very constant, and noticeable even 
 in the formation of the branch-like division of the ovary, " although he 
 will not venture to define them." He adds, further, that they have 
 no connection with the constitution of their host, but that it rather 
 appears as though the degree of frequency of both varieties were 
 determined by the locality. 
 
 Later helminthologists have devoted less attention to the fore- 
 going varieties of form, partly indeed because (being for the most part 
 North Germans, especially Kudolphi) they lived and collected in 
 districts where they mainly came across only one form. Their Tcenia 
 solium is pre-eminently the hook-bearing species still designated by 
 this name. It is true that the great variability in the size and nature 
 of the joints was sometimes noted, but it was not perceived that these 
 divergences always occurred only in certain individuals, and charac- 
 terised particular " genera " or " varieties," which we are now accus- 
 tomed to regard as distinct species. 
 
 But of course the less this circumstance was noted, the more sur- 
 prising did it seem that reports multiplied, according to which the 
 head of the human Tcenia was sometimes destitute of the circlet of 
 hooks. It gradually began to appear as though there were, as Batsch 
 had already conjectured, districts, or even whole stretches of country, 
 in which Tcenia solium was never, or only very seldom, found with an 
 armed head. 
 
 Thus Bremser, the famous Viennese helminthologist, reports in 
 his great work 1 that, in opposition to the general descriptions and 
 figures of Tcenia solium, he had sought in vain for the circlet of hooks, 
 and that, in spite of the most minute examination of a great number 
 of tape-worms (in Vienna), he had only seen it in a head sent by 
 Eudolphi from Berlin. A worm with a hook-bearing head was after- 
 wards sent to him from the general hospital. If Bremser had paid 
 attention to the fact that the unarmed worm which he had observed 
 also differed from the armed one in size and structure of the joints 
 (all of his drawings very closely represent Tcenia saginata), the 
 explanation of the lack of hooks might perhaps have been sought in 
 another direction than in the supposition (adopted by other investi- 
 gators, and especially by my uncle, F. S. Leuckart, and Mehlis) that 
 the tape-worm lost its armature with age, as a man loses his hair. 
 
 1 " Lebende Wiirmer im lebenden Menschen," p. 100. 
 2D 
 
418 HISTORICAL ACCOUNT OF TffiNIA. S AGIN ATA. 
 
 Neither did Wawruch ever succeed in finding an example with an 
 armature of hooks 1 among the very numerous tape-wornis expelled under 
 his treatment in Vienna. It is also known that the south of Wiir- 
 temberg, which lies in the basin of the Danube, furnishes almost 
 exclusively the unarmed Tcenia (Weishaar), while the districts drained 
 by the Neckar yield, with but few exceptions, the armed species 
 (Seeger) 2 In Java, Schmidtmliller 3 always found only the unarmed 
 tape- worm, although, during the sixteen years of his residence there, 
 he had opportunity to observe great numbers of them in the negro 
 soldiers. From their description, they are undoubtedly Tcenice, but 
 the worms had, nevertheless, such an unusual appearance, and espe- 
 cially such broad joints, that Schmidtmiiller was tempted to regard 
 them as a special species of the genus Bothriocephalus (B. tropicus). 
 The "broad tape -worms" (Tcenia laid) observed by Tutschek in 
 Tumale (Africa) were probably the same worms. 
 
 But now that we have become convinced that, with the special 
 structure of the head of the human Tcenice, there is also always asso- 
 ciated a characteristic structure of the joints ; in other words, that the 
 Tcenia solium of the helminthologists (and of Linne*) comprehends 
 two distinct species one of them unarmed, with broad and thick 
 joints, and the other armed, and with slender and thin joints. All 
 these statements and observations find a simple and natural recon- 
 ciliation. If only the true relation of these long familiar differences 
 had been sooner understood, science would have been spared many 
 serious errors, for even those which we have already mentioned do not 
 by any means exhaust the whole number. 
 
 The reader will remember that Linne* described by the name of 
 Tcenia vulgaris a form of the modern genus Bothriocephalus, whicli 
 was distinguished from Tcenia lata (Bothriocephalus latus) by the 
 fact that there are two medially situated genital pores. Werner 
 transferred the same name to a tape-worm, of which he met with four 
 specimens in only one case out of about fifty, 4 and which resembled 
 the Linnean species in so far as its joints were also provided with 
 two pores. Although these pores were situated on the margins, and 
 although, from the structure of its joints and head, the worm was 
 decidedly a Tcenia, and not a Bothriocephalus, Werner thought he 
 could identify it with limit's form. 
 
 Batsch, who recognised the impossibility of such an association, 
 proposed the name T. dentata for Werner's worm. 6 He referred it to 
 
 "Praktische Monographic der Bandwurmkrankheit,"-p. 34 : Vienna, 1841. 
 
 "Die Bandwurmer," p. 62 : Stuttgart, 1852. 
 
 Hannoverische Annalen, Bd. vii., p. 602, 1847. 
 
 "Verm, intest. br. expositio :" Lipsise, 1782. 
 
 Loc. cit., p. 185 ; also Gmelin, "Syat. nat.," Edit. xiii. 
 
TCENIA VULGARIS AND T^ENIA DENTATA. 419 
 
 the unarmed species, since in his description Werner said "The 
 existence of a circlet of hooks could not have been overlooked if it 
 had been present with any distinctness." Instead of it, a median 
 papilla is mentioned, lying between the suctorial cups, which 
 recalled those of T. solium, except that they were larger, and visible 
 even to the naked eye. In length, general appearance, and form of 
 the joints these specimens closely resembled the common tape- worm 
 of man, and particularly the broad form (T. saginata), but there was 
 a striking difference between them in the doubling of the marginal 
 pores. 
 
 But since two opposite peripheral openings sometimes occur in 
 the common human Tcenice, especially in T. saginata, and since such 
 joints, like other similar malformations, often repeat themselves 
 several times in the same worm, the supposition of Eudolphi that 
 Werner's worm belongs to the so-called T. solium seems very pro- 
 bable. 1 Joints with two lateral sexual openings are, however, rare in 
 the cystic tape-worms, while Werner credits the whole chain with 
 double openings. It is just possible that the reports in question are 
 due to the observer having erroneously generalised the peculiarities 
 noted, which had never been previously observed. It strikes one as 
 strange that a worm such as Werner describes should have never been 
 rediscovered during the lapse of a century. A Saxon physician, 
 Mcolai, did indeed describe a Tcenia dentata, 2 but this worm, about 
 which Nicolai said only that it " belonged to the rare species Tcenia 
 dentata" thus identifying it, according to Batsch's nomenclature, 
 with Werner's T. vulgaris has only a single generative opening like 
 the ordinary tape-worms. It is, indeed, nothing (as the accompanying 
 description proves) but the common T. saginata, with its unarmed 
 head and characteristic body-form. 
 
 In this Tcenia dentata we find then, for the first time, a well 
 characterised 3 second species of large-jointed Tcenia infesting man 
 a species which is expressly designated as such, and as different from 
 the ordinary Tcenia solium. This difference holds true, however, 4 
 only in regard to " the flat transparent form " (our modern T. solium), 
 
 1 "Entoz. hist, nat.," vol. ii.,p. 76. 
 
 2 Neue Zeitschr. f. Natur- und Heilkunde, Bd. i., p. 464 : Dresden and Leipzig, 1830. 
 
 3 Nicolai diagnoses his species as follows: "Taenia capite inermi acuminate sessili, 
 articulis dilatatis brevioribus, marginis utriusque lateris medio elatiore, alterius osculato, 
 majoribus transverse striatis, emarginatis." 
 
 1 Nicolai was, indeed, quite unaware of this fact, and we can therefore understand his 
 report when he says that the host of the Tcenia dentata, shortly before expelling the 
 latter, voided also "a piece of Tcmia solium with unusually large joints, and about six 
 inches long " a piece which was obviously only the terminal portion of the subsequently 
 voided worm. 
 
420 HISTORICAL ACCOUNT OF T^NIA SAGINATA. 
 
 for the common form with thick broad joints the Tcenia solium of 
 the ancients is as truly identical with this Tcenia dentata as with 
 the Botliriocephalus tropicus of Schmidtmiiller. 
 
 Neither Nicolai nor Schmidtmiiller was able to make out a good 
 case for the specific distinctness of his worm. Their reports were 
 but little noticed, and for the most part, indeed, entirely overlooked, 
 so that the worms they had observed were, as before, referred to T. 
 solium if they were alluded to at all. 
 
 This was the state of matters till, in 1852, Kiichemneister again 
 advanced the opinion that besides Tcenia solium there was another 
 large-jointed species to be distinguished in man. 1 Both were, he 
 said, well marked by distinctive and constant characters, partly in 
 shape, partly in the structure of the head and of the uterus. Only 
 one, the Tcenia solium, is provided with hooks ; the other, which is 
 also the larger and broader, is unarmed. 
 
 If Ktichenrneister had been better acquainted with the literature 
 of Helminthology, and had consulted it more carefully, he would very 
 soon have learned that his discovery was not so new as he supposed, 
 but was rather only a confirmation and extension of observations 
 which would have been long since fully settled if the observers had 
 had a more rich and complete material to work upon. He would also 
 have learned that the species described by him as new, and named T. 
 mediocanellata, was nothing but the true T. solium* the "familiar" 
 tape-worm of the old helminthologists, the T. grandis saginata of 
 Goze. This fact is not in the least altered by the circumstance 
 that later zoologists have, in opposition to the common use of the 
 term, come to refer the designation Solium to the flat transparent 
 form (T.plana pellucida of Goze) first clearly defined by Linne". This 
 is mainly due to the influence of Kudolphi, who, in Greifswald and 
 Berlin, was able to procure only the latter form, 3 and was thus misled 
 into the supposition that the long-jointed tape- worms of man belonged 
 one and all to the same species. 
 
 Strictly speaking, then, Kiichenmeister's T. mediocanellata should 
 be called T. solium ; but it would thus be necessary to find a new 
 
 1 See especially, "Ueber die Cestoden im Allgemeinen und die des Menschen insbe- 
 sondere," p. 85 et seq., Zittau, 1853, and " Parasiten," Bd. i., p. 82, Leipzig, 1855. 
 The third species mentioned in the latter passage " the Tcenia from the Cape of Good 
 Hope " has been withdrawn since I recognised it as merely a malformation. 
 
 2 The Tcenia lata mentioned by Kuchenmeister can scarcely be referred to T. media- 
 canellata. It is, as we have shown, merely our modern Bothrioceplialus, erroneously 
 credited with the head of T. saginata. 
 
 3 That Rudolphi had also seen the true Tcenia solium (T. saginata), may be inferred 
 from his record of two specimens which were, on account of their size, ranked beside the 
 T. rulgaris of Werner, " Entoz. hist, nat.," t. ii., p. 76. 
 
RECTIFICATION OF NOMENCLATURE. 421 
 
 designation for the armed species, which has been generally known 
 by the latter name in modern zoology. One might perhaps call it 
 Tcenia pellucida, following Goze's diagnosis. But by this change of 
 name the confusion in the nomenclature of the tape- worms, which is 
 already great enough, would only be increased. I feel myself, there- 
 fore, constrained along with Kuchenmeister, in the interests of 
 scientific intelligibility, to uphold the name of Tcenia solium for the 
 armed form. 
 
 It is thus the unarmed form which has to receive another name. 
 Kuchenmeister has, as we have seen, chosen for it the designation 
 Tcenia mediocanellata, which has since been frequently adopted. -He 
 confesses, however, himself that the choice is "not a very happy 
 one," since it suggests the erroneous opinion which he at first upheld, 
 that the uterine stems of the joints were united together into a com- 
 mon longitudinal canal. It must also be noted that Kuchenmeister's 
 T. mediocanellata had previously received, as we have seen, many 
 other names. Thus, besides such names as Tcenia lata ( T. inermis, 
 Brera) and Botliriocephalm tropicus, which we may leave out of 
 account since they rest on false presuppositions, it has been called 
 T. grandis saginata by Goze, and T. dentata by Nicolai. It is surely 
 not only justifiable, but really demanded, by the rules of zoological 
 nomenclature, that the thoroughly unsuitable designation "medio- 
 canellata" should be replaced by Goze's very appropriate name 
 " saginata" as I proposed some years ago in my reports on the pro- 
 gress of the natural history of the lower animals. 1 Since this name 
 has, in the meantime, been generally accepted e.g., in Glaus' 
 " Zoology " and Moniez's " Monograph," and has even obtained cur- 
 rency in medical writings through Lewin and Heller, and since 
 Kiichenmeister has himself declared that he was prepared to accept 
 any name more suitable than his own, I have no scruple in using the 
 name Tcenia saginata. 
 
 Though Kuchenmeister's investigations on the Tcenice have now 
 been rewarded by the appreciation they deserve, it ought to be men- 
 tioned that his newly described and, as it appeared, newly discovered 
 " T. mediocanellata " was not at first recognised on all hands. A few 
 investigators declared themselves distinctly in favour of ranking it as 
 a distinct species, and sought to corroborate their opinion by investi- 
 gation and experiment. Of these were such men as the elder van 
 Beneden and A. Schmidt in Frankfort. 2 Others, on the contrary, 
 remained neutral, or cast doubts upon the constant association of the 
 characters upon which Kuchenmeister relied, or would at most regard 
 
 1 Archivf. Naturgesch., Jahrg. xxxiii., Bd. ii., p. 284, 1867. 
 - See the first German edition of this work, Bd. i., p. 238. 
 
422 HISTORICAL ACCOUNT OF T^INIA SAGINATA. 
 
 T. mediocanellata as a variety of the ordinary T. solium. Thus, 
 Weinland, among others, reports that in an American tape-worm, 
 which in size and structure of the head was exactly like Kiiehen- 
 meister's species, he found precisely the same form of uterus as in T. 
 solium. 1 He regards T. mediocanellata only as a common tape-worm, 
 which has by chance, or perhaps in consequence of a sudden wrench, 
 lost its rostellurn with the hooks, and had therefore, by continuous 
 use, gradually increased the size and strength of its suckers, the only 
 remaining organs of attachment. The large size and thickness of the 
 worm are consistent with such a supposition, since it is quite plausible 
 that these forms, presenting a large surface to be affected by the 
 pressure of the intestinal contents and the contraction of the in- 
 testinal wall, should therefore be most exposed to the danger of losing 
 their circlet of hooks; and the same factors which determine the 
 large size of the body, may possibly also be the causes of the abundant 
 branching of the uterus, for that represents after all only the space- 
 requirement of a great mass of eggs. 
 
 All these suppositions and hypotheses were, however, dismissed 
 when I succeeded, some years after Kiichenmeister (1861), in rearing 
 the young form of Tcenia saginata* and establishing that the worm in 
 question differs in its development from Tcenia solium in a way as 
 characteristic as it is striking. While the latter, as we first knew 
 from Kiichenmeister, is in its youth the familiar bladder-worm of the 
 pig (Cysticercus cellulosce), the young T. saginata is found not in the 
 pig, but in the ox, as a hitherto unknown muscle bladder- worm, which 
 is from the first destitute of hooks and of a rostellum, and is other- 
 wise very different, especially in the size and structure of the rudi- 
 mentary head. 
 
 By this demonstration, the question as to the nature and inde- 
 pendence of Tcenia saginata has been settled. To-day it is universally 
 recognised as a species distinct from Tcenia solium, a species, 
 moreover, which has a much wider distribution than the latter, 
 indeed occurring wherever the ox is a domestic animal, and where 
 its flesh is used as food. We find it in all countries, both in Temperate 
 and Torrid Zones, and know that in districts where it is the custom to 
 eat raw or almost raw flesh, as in Abyssinia, almost every one suffers 
 from it from their earliest years. Tcenia solium stands in the same 
 relation to the pig as T. saginata to the ox, but is less common, since 
 the breeding of swine is not so general as that of the ox, especially in 
 hot countries. 
 
 1 "Essay on the Tape-worms of Man," p. 40: also, Med. Corrcspondcnzblatt des 
 wiirtemb. drzti. Vereins, p. 31, 1859. 
 
 2 Oottingen Nackrichten, Nos. 1 and 2, 1862. 
 
 
STRUCTURE OF THE PROGLOTTIDES. 
 
 423 
 
 Growth and Structure of Tsenia saginata. 
 
 Sommer " Ueber den Bau und Entwickelung der Geschlechtsorgane der Tsenia medio- 
 canellata," Zeitschr.f. wiss. Zool., Bd. xxiv., p. 499, 1874. 
 
 The designation " grandis saginata" which Goze has given to this 
 species, in contrast to the one which we now call Tcenia solium (his 
 " plana pellucida "), gives at once an idea of the characteristic 
 size and appearance of the worm. It is natural, then, that the 
 characters expressed by these words should be first used for specific 
 diagnosis. 
 
 We must not forget, however, that these peculiarities are not 
 always equally conspicuous. We find specimens, for instance, which, 
 though perhaps of the normal length, have by no means the charac- 
 teristic appearance, being far thinner and almost transparent, so that 
 they might be readily referred to Tcenia solium, were it not for the 
 absence of hooks on the head, and the frequent ramification of the 
 uterus. 
 
 As a rule the physician has not in his diagnosis to deal with the 
 whole worm, but only with the isolated proglottides. The identifi- 
 cation of the latter is a matter of great importance, since the Tcenia 
 saginata is very different from T. solium, both in its pathological and 
 therapeutic aspects. For the latter involves much greater danger to 
 the patient, for reasons which will presently appear, and is therefore 
 to be removed as expeditiously as possible, while T. saginata admits 
 of a more temporising mode of treatment, which is the more fortunate 
 since the worm in question, though hookless, has a considerable power 
 of resistance, and is only to be dislodged by very powerful and 
 energetic means. 
 
 FIG. 240. Isolated proglottides of Tcenia saginata (nat. size). 
 
 The Proglottides. It is of some aid in diagnosis to note that the 
 proglottides of T. saginata are by no means so exclusively expelled in 
 the stools as those of T. solium ; in great part, indeed, they leave the 
 host spontaneously, which is very rarely the case with the latter. 
 
424 GROWTH AND STRUCTURE OF T.ENIA SAGINATA. 
 
 This power is due to the strong development of their musculature, 
 which ensures a considerable mobility. This muscular development 
 is shared of course by the whole body, and contributes not a little to 
 the thick and fat character which we have already repeatedly 
 emphasised as one of the characteristics of T. saginata. Even after 
 leaving the intestine the proglottides retain for a while their mobility, 
 and creep about in a definite direction till the continued lowering of 
 temperature brings them to a stand-still. In lukewarm water their 
 movements can be followed for hours. They move just like indepen- 
 dent organisms, and were indeed formerly regarded as such ( Vermcs 
 cucumerim). In the warmth of the bed they often creep over the 
 whole body, especially if the skin be somewhat damp. The pro- 
 glottides which Pallas detected on the wall, more than a yard above a 
 patient's bed, were probably those of T. saginata, and not those of the 
 less muscular T. solium. 
 
 Although it is always only the last and oldest joints which 
 become separated from the chain and wander outwards, they are by 
 no means always the largest. This is due to the fact that they 
 generally lose a more or less considerable portion of their contents 
 just when the separation commences, and are indeed occasionally 
 liberated almost destitute of their eggs. As a rule, it is at the anterior 
 border of the joints that the eggs escape, which is explained by the 
 circumstance that it is at this point that the uterus, with its longi- 
 tudinal canal and lateral branches, is most closely approximated to 
 the surface, and is therefore most easily ruptured by the pressure of 
 the contracting muscles. While the joint creeps about, the eggs are 
 sometimes seen issuing in a stream from this point. 
 
 The decrease in size which ensues in consequence of the expulsion 
 of the eggs, expresses itself in a diminution of the transverse diameter, 
 which is sometimes (Fig. 237) contracted to less than 4 mm., and oc- 
 casionally so much that the proglottides look quite cylindrical. Empty 
 joints of this rounded form have been repeatedly sent to me as " thread- 
 worms," although the nature of their body-parenchyma, and the 
 constant distinctness of the lateral ridges, made their true nature 
 at once obvious to the expert 1 . 
 
 So long as the animals retain their mobility, one can observe a 
 perpetual change of form ; they are at one time stretched out and 
 nearly cylindrical, and again they are contracted into a club or flask- 
 like form, till finally they become short, flattened, broad, quadrangular 
 bodies, still possessing a quite appreciable thickness, and recognisable 
 in form and character as tape-worm segments. Throughout these 
 
 1 Even a helminthologist must be reproached with having confused these joints with 
 Oxyuridse ; see Coulet, " Tractatus de Ascaridibus et Lumbrico lato : " Lugd. Bat., 1729. 
 
CHARACTERISTIC STRUCTURE OF THE UTERUS. 425 
 
 varied changes it is the anterior end which is most affected. It is at 
 
 one time pointed like a cone, at another it is spherical, and again 
 
 it is flattened like a spatula, as is the cephalic ^ -_- 
 
 end of certain Planarians. It resembles the / | 
 
 latter also in going first as the animal 
 
 creeps. The more truncated posterior end 
 
 changes its form but slightly, and with its 
 
 everted border, which formerly embraced the 
 
 adherent joint like a cuff, forms a distinct ^^ 
 
 sucker, by which the animal fixes itself FlG . 2 4i.-Pro g lottides of 
 
 during its Creeping movements. 1 Elongation Tcenia saginata in motion 
 
 and contraction succeed one another so ^ nat> slze '' 
 rapidly that in a minute the joint can cover a distance of several 
 centimetres. By unequal distribution of the contractions over the 
 two halves of the body, the direction of motion is not unfrequently 
 turned to the one side or to the other. 
 
 The outer surface of the body is frequently wrinkled longitudinally, 
 and is of a dirty white colour. The rusty brown eggs can sometimes 
 be seen shining through the thick envelope of the body. 
 
 The Structure of the Uterus, which, with its numerous lateral 
 branches, is so characteristic of T. saginata, is best examined by 
 treating the proglottides with acetic acid, or with caustic potash, and 
 then holding them against the light, pressed between two glass plates. 
 
 In such preparations one observes first the median stem of the 
 uterus as a wide, though not uniformly filled, longitudinal canal 
 running up the middle of the joint. It extends forwards almost as 
 far as the outer wall, while posteriorly it stops short of it at a 
 
 1 This happens even in the segmented condition, according to an observation made by 
 Goze on T. crassicollis (loc. cit., p. 346), which may be quoted as showing the great 
 mobility of these animals. " I hung a worm," he says, " head downwards in a long 
 cylindrical glass full of water, and with its posterior end attached to a thread over the 
 margin of the glass, and watched it. First it stretched out its head-bladders (suckers, 
 see Fig. 223) like the horns of a snail, as I previously observed in a segmented cystic 
 worm from the liver of the mouse (Cysticercus fasciolaris, Fig. 202). Then the border of 
 this upper part which was hanging down became for a short time crumpled, so that it 
 looked like a Savoy cabbage ; but this movement did not last long. Thirdly, it made a 
 mancBuvre which astonished me. Feeling apparently that the water was not its native 
 element, it tried to get out. With the lower rim of the last joint of the outside portion it 
 firmly fixed itself to the glass. Then with incredible rapidity it contracted into a few lines 
 the contiguous stretch of joints which were partly under water. The breadth was thereby 
 very considerably increased to almost an inch, and this whole stretch of joints was lifted 
 out of the water. The formerly fixed joint was then relaxed, and the contracted portion 
 elongated again, so that it now hung over the glass. In the same way the middle portion, 
 and finally the cephalic end, were lifted up out of the water. In three contractions it lay 
 onthe ground near the glass. From this movement we can understand how a worm, 
 especially a human one, can work its way back into the intestine, even when it has been 
 so far expelled that a long piece of it hangs out from the rectum or anus." 
 
426 GROWTH AND STRUCTURE OF T.ENIA SAGINATA. 
 
 considerable distance (3 to 4 mm.). From this main stem there 
 spring on either side about twenty to thirty branches, which succeed 
 each other at short distances, and with few exceptions extend over the 
 whole of the middle portion to the inner boundary of the cortical 
 layer, close to which they all end blindly. If we except the terminal 
 branches at each end, they all spring almost at right angles from the 
 main stem, only bending occasionally forwards or backwards, and 
 exhibiting many minor twists corresponding to the numerous second- 
 ary divisions which they give off in their course. The number of 
 definite branches is about eighty and more, but it must also be noted 
 that the side at which the peripheral pore is situated has always a 
 somewhat smaller number, since two lateral branches have usually 
 been replaced by the vas deferens and vagina about the beginning of 
 the posterior two-thirds of the proglottis. The proximal and distal 
 primary branches have their processes bent round from the transverse 
 direction towards the ends of the proglottis, to which those in the 
 longitudinal axis are indeed almost at right angles. This is of course 
 most striking at the posterior end, where both the 
 branches themselves and their processes are of 
 considerable length, and are grouped on either side 
 in an almost fan-shaped manner. The triangular 
 space remaining in the middle between the two 
 halves is only incompletely occupied by longitu- 
 dinal ramifications. 1 
 
 It is hardly necessary to note that the eggs, 
 lying somewhat freely within the uterus, are very 
 FIG. 242. Uterus unequally distributed according to the direction of 
 of a free proglottis. the muscular pressure. Sometimes one branch, 
 sometimes another, is specially full and distended, 
 and the blind ends are not unfrequently swollen like clubs. But 
 the characteristic appearance of the uterine ramifications is never 
 hidden, nor are the distinctions obliterated which obtain between 
 this species and T. solium. The most hasty comparison of the 
 structure of the uterus in the two is, as a rule, quite enough for 
 correct diagnosis. 
 
 I say, as a rule, for sometimes it must be allowed that there is a 
 certain variability in the structure of the uterus. On the one hand, 
 there are cases of T. solium in which the lateral branches of the 
 uterus are more or less abnormal in number, and on the other hand, I 
 
 1 The first satisfactory observations on the nature of the uterus in Tcenia saginata are 
 those of Platner, who has given us a thorough if not exhaustive account of the structure of 
 the generative organs ; " Anat. Untersuchungen Uber den menschlichen Kettenwurm," 
 MiiUer's Archiv f. Anat. u. Physid., p. 275, 1859. 
 
ABNORMAL SIMPLICITY OF THE UTERUS. 
 
 427 
 
 have seen specimens of T. saginata in which the formation of the 
 
 uterus, owing to reduction of its lateral branches and the obliteration 
 
 of the accessory twigs, somewhat resembled that of T. solium. Yet I 
 
 must assert that I have never been in the least doubt as to the great 
 
 majority of the preparations and worms which I 
 
 have examined; not even in the case of the 
 
 worm which I have represented as faithfully as 
 
 possible in the accompanying figure. In spite 
 
 of the comparatively simple structure of the 
 
 uterus, I considered it from the first as T. 
 
 saginata, and the corroboration of my diagnosis 
 
 was finally furnished by the expulsion of the 
 
 head. The joints of this (unpigmented) worm 
 
 were all of the above structure, indeed I have 
 
 never found a tape-worm all the segments of 
 
 ,., . . ,,. FIG. 243. Joint of a 
 
 which were not uniform in this respect. T saginata with unusu- 
 
 Whether or not the simplification of the aU J simple structure of 
 
 m . ,.-n ., the uterus, (x 2.) 
 
 uterus in T. saginata may go still further, must 
 remain uncertain. Weinland reports having found an American 
 tape-worm which in size and head-structure belonged to this species, 
 and yet had exactly the uterus of T. solium.' 1 
 
 Of course it is not only the proglottides which are capable of 
 great mobility and contractility. The whole tape-worm possesses 
 these properties in a corresponding degree, as is to be inferred from 
 the uniform arrangement and development of the musculature 
 throughout the chain. 
 
 Such being the case, the measurements of tape- worms yield very 
 varied results, according to the state of contraction. We have given 
 the length of Tcenia saginata in our diagnosis as from 4 to 8 metres, 2 
 and have explained the reported variations as due to the varied ex- 
 tension of the worm, but we must also note that the varying number 
 of ripe proglottides has also much influence in determining the length. 
 On the other hand, we should have only a very incomplete idea of the 
 effects of muscular action if we were to limit them by stating that 
 the extreme dimensions are in the ratio 1 : 2. Goze saw a portion of a 
 
 1 "Essay on the Tape-worms of Man," p. 40, Fig. 8, Boston, 1858; Med. Corresp.- 
 Bl d. wiirtemb. drztl. Vereins, p. 31, 1859. 
 
 2 According to Bremser and Diesing, the famous Viennese collection of Helminths 
 contains chains 20 to 24 feet long, very much longer, therefore, than the preserved speci- 
 mens I have measured, which were at most only slightly above 14 feet. Bremser reports 
 having seen still larger worms. The older results, according to which Tcenia solium (i.e., 
 generally Tccnia saginata) grew to 40, 50, and even 800 yards, are generally regarded as 
 erroneous. They have apparently added up every portion of the worm at any time 
 evacuated, and thus attained a result so colossal that it could not be contained at one time 
 in the human intestine. 
 
428 GROWTH AND STRUCTURE OF T^INIA SAGINATA. 
 
 large tape-worm from the cat (which is not more muscular than the T. 
 saginata), six inches long, contract "with incredible rapidity" to a length 
 of a few lines, and the whole worm, after having been only three 
 inches long, when put into lukewarm water extended itself again to a 
 yard and a quarter. 1 
 
 The contraction is not uniform over the whole length. One some- 
 times sees, indeed, that the whole worm shortens powerfully and 
 suddenly, if it be, for instance, rapidly transferred from the warm 
 intestine to cold water or spirits. Similarly, one sometimes sees a 
 wave of contraction pass continuously backwards or forwards over a 
 long series of joints. Not less frequently do we find that the play of 
 motion is confined to a short portion, or to a few joints, which thus 
 manifest before their separation that morphological and anatomical 
 independence which is also (see p. 293) expressed in the arrangement 
 of the muscles of the body. Not unfrequently one finds neighbouring 
 portions and joints in quite different states ; some broad and much 
 contracted, others long and drawn out into thin bands, and may even 
 observe that not only the anterior and posterior ends, but the two 
 sides of the same segment, are in form and motion somewhat inde- 
 pendent of one another. 
 
 We need not emphasise the close connection between the number 
 of the ripe proglottides and the length of Tcenia saginata. The 
 number varies greatly in different cases. Even the number of pro- 
 glottides expelled daily from the affected patients may vary from seven 
 or eight up to twelve, although the growth is on the whole very uniform, 
 a head producing in about three months a chain of about 1300 joints, 
 and therefore about fourteen daily. It is thus evident that the number 
 of ripe proglottides would be continually on the increase, were it not 
 that there occurs from time to time a specially copious expulsion. 2 
 On the other hand, we must also take into account that the formation 
 of new joints in the adult tape- worm will perhaps occur less rapidly 
 than was the case during the development of the chain, for in the 
 adult the relation of the nutritive absorptive surface to the growing 
 mass is ever becoming more unfavourable. It is possible, further, 
 that varying nutritive conditions may in some cases determine an 
 unequal growth. 
 
 The general growth and gradual increase in size of the joints, and 
 their influence upon the appearance of the worm, may be most con- 
 veniently discussed by taking a concrete example. I will, in the 
 first place, refer to a specimen in the collection at Leipsic, which 
 in a comparatively contracted state measures 485 cm., and is com- 
 
 1 Loc. tit., pp. 345-346. 
 
 - This supposition is confirmed by the results of Schimper's experience in Abyssinia. 
 
DIMENSIONS OF TVENIA SAGINATA. 
 
 429 
 
 posed of 1318 joints. Close behind the head, which has a size of 
 1-7, the neck is 0'8 mm. broad, and at a distance of 5 cm. it has 
 grown to 1*5 mm. The first 6 to 8 mm. are destitute of any clear 
 segmentation, but after that the segments follow each other so closely 
 that 270 can be distinguished within the 5 cm. just referred to. In 
 spite of this very considerable number, the last joints have a length 
 of - 5 mm., which by the end of the second length of 5 cm. (380th 
 joint) has risen to 0'8 mm., with an associated breadth of 3 mm. 
 The next 25 cm. contain fewer joints than did the first 10 viz., 247, 
 of which the last are 1'5 mm. long by 5 mm. broad. Henceforward 
 the size rapidly increases, while the number of joints sinks in pro- 
 portion. Thus, taking successive lengths of 50 cm. each, we have 
 the following results : 
 
 36 85 cm. contained 180 joints, of which the last was 4 mm. long by 10 mm. broad. 
 
 86135 
 136185 
 186235 
 236285 
 286335 
 336385 
 386435 
 436485 
 
 135 
 107 
 91 
 83 
 64 
 53 
 48 
 30 
 
 4-5 
 
 12-5 
 
 5 
 
 13-5 
 
 6 
 
 14 
 
 7 
 
 13 
 
 9 
 
 12 
 
 14 
 
 7'3 
 
 15 
 
 7 
 
 19 
 
 5 
 
 The last 249 cm. contain not more than 278 joints a marked 
 contrast to the anterior 235 cm. in which there were 1040. The 
 above measurements also show that the greatest breadth occurs about 
 the middle of the body. From that point it decreases both anteriorly 
 and posteriorly, and posteriorly although the length always continues 
 to increase, which is to be regarded rather as the result of an extension 
 than of growth. It is only in the last 100 joints that the length 
 exceeds the breadth. 
 
 When the state of contraction alters, then the relation of length 
 to breadth must also alter. We can best perceive this by direct 
 measurement, such as is again afforded us by a much contracted 
 specimen only 206 cm. long in the Zoological collection at Leipsic. 
 
 The contracted state of this worm is most plainly seen at the neck, 
 which passes anteriorly without any marked decrease in size into 
 the head (which measures about 2 mm.), and at a distance of 6 cm. 
 behind possesses a breadth of 4 mm. The segmentation can be 
 followed almost to the head, although the number of the segments 
 is at first difficult to determine. I do not think, however, that I am 
 far from the true facts of the case when I credit the foremost centi- 
 metre with about 200 segments. The number is greater than that of 
 the succeeding 5 cm., which only exhibit 186. The length of the 
 joints has, however, increased proportionally, rising from O'l mm. at 
 
430 GROWTH AND STRUCTURE OF TCENIA SAGINATA. 
 
 the beginning of this series of joints to 0'5 mm. at the end. Twenty- 
 five cm. further back, and therefore at a distance of 31 cm. behind 
 the head, the breadth of the body has increased to about 10 mm. 
 There were 376 joints in this length, but the greater part of these 
 were in the anterior 12 cm., for the length of the joints increases 
 posteriorly very nearly up to 2*6 mm. The remaining 150 cm. were 
 composed of 321 segments, of which the three successive lengths of 50 
 cm. contained 170, 91, and 63 respectively. The length and breadth 
 of the last segment of each division were expressed by the following 
 ratios: 4-3 : 11-5, 7 : 11, 12 : 6-5. 
 
 The total number of segments in this worm was about 1083, but 
 it is not perfect, having lost its posterior end, perhaps in connection 
 with the strong contraction which it has undergone. A comparison 
 with the worm first measured would lead us to conjecture that this 
 end measured about 200 cm., and was composed of perhaps 200 
 proglottides, so that we may fairly attribute to this animal a length 
 of about 400 cm., and about 1300 joints. 
 
 Earlier computations all fall short of this result. In the first 
 edition of this work, at a time when I had seen no perfect specimen 
 (with the head), I estimated the number at about 1000. Dr. A. 
 Schmidt in Frankfort counted on a worm of " not very great size " 
 1058 joints, including 100 ripe proglottides, and Sommer, who has 
 most intimately examined the Tcenia saginata, fixes the number at 
 1221. The differences seem more considerable than they are in 
 reality, for they result simply from the circumstances that the anterior 
 segments, which can only be made out with difficulty even with the 
 microscope, have been left out of account, and that the computation 
 has in fact begun at a varying distance behind the head. 1 But a 
 single centimetre sometimes makes a difference of more than a hundred 
 joints. And since neither Schmidt nor Sommer have given any de- 
 tailed report as to the nature of their " first " joint, I think we may 
 assume that the most anterior portion has been left out of account. 
 An absolutely correct computation is thus impossible, for the segmen- 
 tation begins so gradually that the determination of the first joint is 
 an exceedingly doubtful matter. 
 
 The boundaries of the individual joints are marked at first by 
 simple furrows. These, though at first but shallow (Fig. 244), after- 
 wards become somewhat deep, and are not exactly perpendicular to 
 the long axis of the worm, but rather inclined forwards at an acute 
 angle, so that the posterior border of one segment overlaps the 
 beginning of its successor like a cuff. The arrangement may indeed 
 
 1 Kuchenmeister in his first work (p. 112) describes the foremost joint of his Tcenia 
 mediocandlata as 1 mm. long by 3 broad. 
 
MODE OF CONNECTION OF THE SEGMENTS. 
 
 431 
 
 FIG. 245. 
 
 FIG. 244. 
 
 be compared to a joint, the anterior portion of each segment fitting 
 into the preceding one like the head of a bone into its socket. We 
 have already noted the histological peculiarities of this connection 
 (p. 293). Posteriorly the re- 
 lative size of this connecting 
 portion decreases, and that the 
 more conspicuously as the 
 joints increase in size, until 
 finally in the free proglottides it 
 becomes hardly distinguishable. 
 We need hardly specially 
 mention that the boundaries of 
 the segments are not to be 
 confused with the transverse 
 furrows which traverse the sur- 
 face, especially in the much 
 contracted condition. It is 
 indeed only in regard to the 
 short somewhat less developed 
 anterior joints that this con- 
 fusion is possible, for posteriorly 
 the projecting borders of the 
 joints (which are of considerable 
 length, of 0*5 mm. or more), 
 render any such mistake im- 
 possible. At first the segments 
 exhibit only a single transverse 
 furrow, which runs across about 
 the middle, and can be followed 
 
 T ' iaginata in a stafce of 
 
 FIG. 245. Longitudinal section through T. 
 saginata (a young chain). ( x 25.) 
 
 into the developing porus genitalis ; afterwards, when the joints 
 become longer, the number of these furrows increases, until they 
 finally disappear in consequence of the longitudinal elongation. 
 
 The Development of Sexual Organs, as well as that of other parts 
 of the body, is associated with the increase in size of the segments in 
 a manner to which we have already alluded. It is more than a 
 mere temporal relation that obtains between the two processes. The 
 formation and development of the sexual organs have a most un- 
 mistakeable influence on the form of the joints and of the whole chain. 
 This is most evident in connection with the specially long or extended 
 joints, which owe their particular shape in great part to processes 
 occurring within the uterus, and essentially amounting to this, that 
 the eggs, with their maturity, attain at the same time their maximum 
 size, and then collect principally in the median longitudinal stem. 
 
432 GROWTH AND STRUCTURE OF TJKNIA SAGINATA. 
 
 The first rudiments of the sexual organs appear somewhat early, in 
 about the 200th joint. The processes of formation and growth, as 
 observed by Sommer, are very like those which I stated in the first 
 edition of this 'work, in regard to T. solium. The full development of 
 the reproductive organs is signalised and completed by impregnation 
 and passage of the eggs into the uterus. These two events are sepa- 
 rated from one another by a distance of about a hundred joints. The 
 development progresses over almost 450 joints, for the first egg in the 
 uterus is observed about the 640th. 1 Shortly before copulation, which 
 takes place at the 516th joint, the porus geuitalis and its papilla are 
 formed, whilst the peripheral depression is visible about 100 segments 
 earlier. 
 
 The proper sexual maturity occurs when the chain has acquired 
 about half its total number of joints, at a point which is indeed far from 
 representing the middle of the adult worm, but in fact, in the above- 
 mentioned specimens, lies only about 30 to 38 cm. from the head. The 
 joints concerned are all characterised by a very appreciable and dis- 
 proportionate increase in breadth. 
 
 This state of matters alters as soon as the eggs pass into the 
 uterus. The median canal, which at this time constitutes the whole 
 uterus, stretches out increasingly as it becomes packed with eggs. In 
 consequence of the pressure, the form of the joint becomes approxi- 
 mately rectangular, and that the more markedly, as the number of 
 eggs continues for a good while to multiply, and, with the incipient 
 embryonic development, their size becomes greatly increased. The 
 uterus, however, does not remain a simple tube ; at the 700th joint, 
 at the point where the formerly abundant testes begin to degenerate, 
 a number of protuberances appear at the sides of the tube. These 
 elongate into the space which now becomes free, and as the testes dis- 
 appear, the uterine processes finally occupy the whole space. The 
 eggs continue to be pushed forward on to the 930th joint, up to which 
 point the female germ-producing organs still retain their full develop- 
 ment. Afterwards they too become wasted, and then only do the 
 branches of the uterus begin to assume their final form. At this time, 
 too, one even finds some eggs with hook-bearing embryos; but 
 the number of these is small at first, till 150 segments further back it 
 begins to increase until the 1100th. Here by far the greater number 
 have gone through their primary metamorphosis, and are inclosed in 
 the embryonic shell. 
 
 The full development of both eggs and uterus occurs, of course, 
 
 1 My computations differ somewhat, as I have explained, from those of Soinmer, 
 who finds the first rudiment of the sexual organs in the 140th joint, the impregnation in 
 the 482d, and the first occurrence of eggs in the uterus in the 581st. 
 
THE STRUCTURE OF THE HEAD. 
 
 433 
 
 only in the last portion of the chain, where the demands for space 
 made by the young brood reach their maximum, and the proglottides 
 gradually prepare for their liberation by the continued contraction of 
 their transverse musculature. 
 
 The Head. Passing to the consideration of the parts of the body 
 in detail, we may first note that the head is comparatively large, and 
 distinctly recognisable by the naked eye. In one of my specimens the 
 head was about 2 mm. broad, by about 1*5 thick. Other specimens, it is 
 true, fall far short of this, and since this smaller size is most marked in 
 the bladder- worms, one of which had a head measuring hardly 1 mm., 
 we may infer that the age of the worm is an important factor in 
 determining the size of the head. 
 The head of Tcenia saginata only 
 reaches its full developement subse- 
 quently during the tape- worm stage. 
 
 But it is not the size merely 
 which varies in the different forms. 
 The form and nature of the neck also 
 vary according to the state of con- 
 traction. Even Bremser notes that 
 the latter is in constant motion, and 
 retains the form it possessed at 
 death. When the worm is suddenly 
 killed when in an active state of 
 vitality, the neck is found shortened 
 and broad, almost as broad in fact as 
 the head, which at first sight looks 
 exactly like the truncated end of the 
 neck (Fig. 246 A). On the other 
 hand, the specimens killed slowly in 
 some more indifferent fluid have a 
 long slender neck, which passes back- 
 wards, gradually broadening into the 
 jointed body, while in front it is 
 sharply separated from the head. The latter appears in such cases as 
 an independent appendage of an almost pear-like shape, somewhat flat 
 in front, with rounded border, and a narrow conical basal portion 
 attached to the neck as to a stalk. The largest part of the head is 
 occupied by the cylindrical suckers which measure 0'8 mm. in diameter. 
 After death these are generally retracted ; while in life they are 
 frequently protruded " like a snail's horns." Their openings are 
 usually greatly narrowed, so that they come to have little more than 
 the third of their equatorial diameter. In the specimens I examined 
 
 2 E 
 
 FIG. 246. Cephalic end of Tcenia sagi- 
 nata in retracted (A), and extended state 
 (B). (x 8.) 
 
434 GROWTH AND STRUCTURE OF T.ENIA SAGINATA. 
 
 they were always directed forwards, so that the muscular mass of the 
 sucker thus came to lie behind the openings, embedded in the paren- 
 chyma of the head, whose form was essentially determined by this 
 circumstance. 
 
 Histologically the suckers only differ from the ordinary type in 
 the special strength of their musculature. The walls have an unusual 
 thickness, and are so firmly united that they can be separated from 
 their surroundings by even gentle pressure. 
 
 But the size and strong development of the suckers are not the 
 only distinctive features in the structure of the head. The absence of 
 the circlet of hooks is not less noteworthy, and determines the re- 
 markable flattening of the apex, which is in such contrast to allied 
 forms; the apical surface of the worm being in no case, however, 
 perfectly level. 
 
 Even Batsch mentions in his Tcenia dentata a " media papilla " of 
 small size lying between the suckers. Similarly, Bremser x saw at 
 this point " an arched protuberance on which one always notices a 
 circle with a small, hardly perceptible, opening in its centre." He 
 regards this circle as rostellum, as may be inferred from the further 
 observation, that it " often, but not always " (that is in Tcenia solium, 
 but not in T. saginata), bears a double circle of hooks. 
 
 I have since shown the truth of this identification. 3 T. saginata 
 does indeed possess a rostellum, as has been amply confirmed both by 
 Nitsche and Moniez. 3 The rostellum is, however, but a small one 
 (0'2o mm.), though essentially agreeing with that of related forms. It 
 consists of a well-defined lenticular body, mainly composed of fibres, 
 which are stretched straight between the two opposite surfaces. They 
 have thus a longitudinal course, and are crossed posteriorly by a 
 system of radial fibres. The muscles which usually run along the 
 under part of the rostellum are only slightly differentiated, and 
 are hardly recognisable as distinct structures, though in arrangement 
 and course they certainly resemble those of allied forms. 
 
 So far, then, the rostellum of Tcenia saginata, in spite of its 
 comparatively weak development, possesses essentially the structure 
 seen in the hook-bearing cystic tape-worms. But, while in the 
 latter the rostellum is covered by a prominent layer of parenchyma 
 
 1 Loc. cit., p. 100. Bremser refers there to his figure (Tab. in., Fig. 3). This is to be 
 referred to T. saginata and not to T. solium, as Kiichenineister would have it (" Parasiten," 
 2d ed., p. 153, note). It was taken from a living hookless specimen by Bremser in 
 Vienna. 
 
 2 First German edition of this work, Bd. i, p. 409. 
 
 8 Kiichenmeister says that this structure has been "first accurately described by 
 Landois and Sommer," but he forgets to say where. In the well-known paper on T. 
 mediocanellata it is not mentioned at all. 
 
FORM AND SIGNIFICANCE OF THE KOSTELLUM. 
 
 435 
 
 FIG. 247. Head of 
 Tcenia saginata in longi- 
 tudinal section, (x 25.) 
 
 in which the anterior processes of the hooks are embedded, this 
 coating is represented in T. saginata only by an annular diaphragm, 
 which lies as a lip on the outer wall of the 
 above-mentioned lenticular mass. This is more 
 or less markedly arched according to the curva- 
 ture of the latter, and has in its centre an 
 opening which is expanded below, and appears 
 sometimes rather deep, since the lenticular body 
 has not unfrequently a depression in its anterior 
 surface. This is the opening long since observed 
 by Bremser, and occasionally by other observers, 
 and the appearance of which has given rise to 
 the formerly prevalent idea that the tape-worms 
 possessed a mouth opening between the suckers. 
 
 I have already noted (p. 351) that the peculiar 
 formation 1 of this structure, as above described, 
 may also be observed at a certain stage in the 
 development of the hook-bearing cystic worms, 
 where it attains its final organization after the 
 hooks and their root-processes have been formed. 
 The state of affairs in T. saginata is therefore 
 far from interrupting the unity of type found in other forms. It 
 either represents in a permanent form the early phase, which has 
 remained undeveloped, or it is the result of retrogression. 
 
 The resemblance is further increased by the fact that the border of 
 the diaphragm in T. saginata is also at first provided with a close circle 
 of little points, that is, with structures such as we saw to be the first 
 traces of the hooks. But the points do not develop, they retain their 
 primary form, and very soon disappear. Kitsche notes, however, that 
 occasionally some of these rudimentary structures persist round about 
 the central pore of the head. 2 
 
 In the first edition of this work I regarded this pore, which I 
 called the " frontal sucker," along with the muscular apparatus lying 
 below it (the rostellum or "bulbus"), as the morphological equivalent 
 of that sucker which is found between the lateral suckers, not only 
 in Rudolphi's Scolex (p. 371) and the associated Phyllobothria, but 
 also in some Ta3niadre. It must not be supposed from this that the 
 
 1 Unlike Kiichenmeister, who finds this structure "sometimes but not always" in 
 T&nia saginata ("Parasiten," 2d ed., p. 180), I have always found it when I looked for 
 it in the right way, and must therefore regard this rudimentary proboscis as a constant 
 character of this worm. 
 
 2 Kiichenmeister's statement ( " Parasiten," 2d ed., p. 180) that Heller has seen 
 twelve, sixteen, or even thirty-two short thick hooks on the head of Cysticercus bovit 
 is incorrect. Heller's observations (see p. 319) referred to many -hooked embryos. 
 
436 GROWTH AND STRUCTURE OF "LENTA SAG IN AT A. 
 
 homologous rostellum of the hooked tape-worms agrees in every parti- 
 cular with a sucker ; yet although this is as clearly stated in my former 
 observations, as now, Kiichenmeister seems to have misunderstood my 
 comparison of the two structures, for he characterises it in his recent 
 work on parasites sometimes as "unfortunate" and sometimes as 
 "incorrect." I can hardly suppose that these epithets will utterly 
 condemn the alleged homology, for this has been, as Moniez em- 
 phasises, established beyond doubt by the developmental history. 
 
 The black coloration, which was long ago observed by Andry, and 
 which occurs much more abundantly in Tcenia saginata than in T. 
 solium, is caused by a granular pigment which is embedded in the 
 connective tissue, and is sometimes found even within the cells. 
 Here and there, according to Virchow, it has a crystalline character. 
 Where it occurs only sparsely it is usually found restricted to the 
 neighbourhood of the suckers, but is sometimes spread over the whole 
 head. Davaine describes as a special variety a perfectly black tape- 
 worm (" Tenia negre ") from the Southern States of North America, 
 
 As to the nature of this pigment, nothing certain is known ; but it 
 is probable that it originates from the colouring matter in the blood 
 of the host, and therefore has the same origin as the pigment of the 
 latter, having a close resemblance to melanin. Its origin can hardly be 
 as simple as Kiichenmeister would have it, when he supposes that 
 those blood-corpuscles which are taken in by the pores of the suckers, 
 and are not used, become changed directly into pigment. 1 - This can 
 hardly be, for the ingestion of blood-corpuscles through the suckers 
 of the Tcenice is more than doubtful on anatomical grounds (p. 304) ; 
 and further, it must be noted, that this embedded pigment is found 
 occasionally even in the bladder-worms, that is, in organisms which 
 are hardly in a position to devour blood-corpuscles as such. In 
 Tcenia saginata, indeed, I have not yet noticed these black -headed 
 bladder-worms, but they are to be found in T. solium, which is, 
 however, on the whole much less copiously provided with the pig- 
 ment. For this reason I think I am justified in assuming that the 
 presence and distribution of the pigment stand in no definite relation 
 to the age of the worm. 
 
 We have already noted that the pigment is not found exclusively 
 on the head, but occurs occasionally on the vagina, vas deferens, and 
 testes. This is the case, however, only in the older proglottides, 
 where the organs in question are no longer functional. 
 
 In such ripe joints one sometimes finds in the cortical sheath 
 accumulations of granular molecules, and also yellow fat-drops, some- 
 
 1 Loc. cit., p. 151, note. 
 
THE VASCULAR APPARATUS. 437 
 
 times in such abundance that the sides exhibit green streaks. This 
 was specially striking in the case of two Tcenice, which one of my 
 Eussian pupils, now Professor P., acquired five years ago in St. Peters- 
 burg, and in which all the proglottides (twelve of which were voided 
 daily) were provided with a green border. 
 
 As to the rest of the organization, there is little, except in regard 
 to the sexual organs, which calls for detailed discussion. We have 
 already mentioned the specially powerful musculature and the very 
 energetic movements. As to the course and arrangement of the 
 fibres, we need only remind the reader that T. saginata was the 
 example we chose as a general type in our detailed description. 
 
 FIG. 248. Head of Cysticercus Teenies saginata?, with frontal sucker and 
 vascular ring. ( x 30. ) 
 
 I cannot exactly confirm the results at which Kiichenmeister 1 has 
 arrived in regard to the vascular apparatus of his Tcenia mediocanellata, 
 according to which it is much simpler in the head than is the case in 
 T. solium. It is indeed true that the ring round the rostellum is, as 
 one would expect, but narrow, yet its structure and arrangement are, 
 for all that, quite normal. Similarly, the four longitudinal canals 
 which form the ring are different only in this respect, that the 
 number and development of the branches are in fact greater than 
 
 1 "Cestoden," &c., p. 110. 
 
438 GROWTH AND STRUCTURE OF T.ENIA SAGINATA. 
 
 usual. The calcareous bodies of T. saginata are also, on an average, 
 larger (up to O'OIS mm.), and more abundant than in T. solium. 
 
 The Structure of tJie Sexual Organs is best observed in joints of 
 medium size (8 to 10 mm. broad by 4 to 6 mm. long), which are in a 
 moderately contracted state approximately rectangular, and belong to 
 the second half of the seventh hundred. They are found, according to 
 the state of contraction, at a distance of about 40 cm. behind the 
 head. They show the generative organs of both sexes in full develop- 
 ment. The copulation has just taken place, and the eggs are begin- 
 ning to pass into the uterus. 
 
 For the purpose of closer examination the fresh joints should be 
 left for a day in ammoniacal solution of carmine of medium concen- 
 tration. After being clarified in glycerine or balsam, one can see on 
 slight pressure all the parts with great distinctness. Apart from the 
 ducts, this is specially true of the female organs, which, with the 
 exception of the median uterus, all lie in the posterior half of the 
 proglottis, and are quite perceptible by transmitted light even to the 
 naked eye. To examine the more intimate structure it is necessary to 
 have recourse to sections, especially to horizontal ones. 
 
 TJie Male Organs. In detail one may note the following char- 
 acters : 
 
 The Testes are first ripe, and consist, as in most Cestodes, and 
 especially in the larger species, of numerous roundish vesicles, which 
 measure on an average about - 15 mm. (from 012 to 0'18), and which 
 fill up all the vacant space in the joint within the vessels. In the 
 anterior half of the joint they are of course much more numerous 
 than behind, where the female generative organs occupy most of the 
 space. Here they are found chiefly at the sides, as is also the case 
 in the anterior half. The vesicles are therefore larger and more 
 advanced along the two sides than the middle of the joint. 
 
 The contents consist partly of long thin adult spermatozoa, 
 which are curled up together in bundles, and usually lie near the 
 wall of the vesicle, with their otherwise hardly defined heads resting 
 on a granular mass. There are also small round balls of varying size 
 up to 0*043 mm., which contain numerous small cells, and represent 
 the early developmental stages of the seminal elements. In the larger 
 balls one can distinctly observe a large clear sphere (0'03 mm.) on 
 which the cells are seated a structure which often occurs in the 
 lower animals as the bearer of the sperm-cells proper. The cells 
 which lie on this to a greater or less extent (nuclei, according to 
 Sommer and Landois), may be observed growing into spermatozoa, 
 while the central sphere itself finally becomes the above-mentioned 
 granular mass. 
 
STRUCTURE OF THE TESTES AND SPERMATOZOA. 
 
 439 
 
 In the small less defined testicular vesicles one finds, moreover, 
 simple nucleated cells, which by growth and endogenous multiplica- 
 tion produce the above-mentioned elements. 
 
 FIG. 249. Generative organs of Tcenia saginata ( x 10.) Male organs. 
 t., testes ; v.d., vas deferens ; c.p., cirrhus-pouch. Female organs. ov., 
 ovary ; y.g., yolk-gland ; m.b., shell-gland (Mehlis' body) ; r.s., receptaculum 
 seminis; ut., uterus; v., vagina; g.p., genital papilla ; cl. y cloaca. 
 
 The testes, when full of ripe spermatozoa, have their original 
 spherical form modified, inasmuch as they are each drawn out at one 
 point into a pointed process, by means of which they are fixed like 
 berries to the ramifications of the vas deferens. The latter is quite 
 conspicuous as in other Cestodes, and its course across the joint from 
 the porus genitalis to the uterus can be followed even with the naked 
 eye, but the processes are, on the contrary, seldom seen with great 
 definiteness. To the older anatomists both they and the testes were 
 alike unknown, and, till F. S. Schultze's discovery, the latter were 
 very generally identified with the vas deferens. 
 
 In favourable specimens we can observe that these processes pro- 
 ceed wholly from the posterior end of the vas deferens. This is seen 
 (Fig. 249) to be continued into a number of thin canals which run in 
 an almost radiate manner from the point of origin, and break up into 
 finer twigs. The majority of these canals belong, of course, to the 
 anterior half of the joint, but some also run backwards. Here and 
 there they become almost varicose by the accumulation of spermatic 
 elements within them. This can be occasionally seen even in the 
 ripe proglottides where the testes have long since degenerated, and 
 
440 GROWTH AND STRUCTURE OF MNIA SAGIN^TA. 
 
 even in some which have spontaneously left the intestine and voided 
 their eggs. This varicose enlargement is to be seen most frequently 
 near the point where they open into the vas deferens or just at the 
 junction, and has been described by Platner, to whom we are in- 
 debted for the most thorough representation of these structures, as a 
 special hollow of irregular jagged form the " spermatic sinus." 
 
 The Vas Deferens itself is a comparatively wide canal with a dia- 
 meter of about 0'025 mm. It runs from the external aperture the 
 porus genitalis across the joint almost as far as the uterus, yet not 
 in a straight course, but, as in related forms, with numerous more or 
 less close coils, which sometimes look as though they were enclosed 
 in a common sheath. I have never been able to observe any special 
 enlargement or seminal vesicle either in the vas deferens or inside the 
 cirrhus-pouch into which the former opens. In the posterior some- 
 what distended portion of the bottle-shaped cirrhus-pouch (about - 4 
 0*5 mm. long) are found a few irregular windings of the vas 
 deferens, which does not exhibit here its usual thick firm walls, but 
 is clad internally with a thick layer of fine chitinous points directed 
 backwards. This structure is obviously adapted for protrusion 
 during copulation, forming the so-called " cirrhus." 
 
 The Cirrhus in Tccnia saginata is very short, so that one only sees 
 it slightly protruded from the porus genitalis. It must, of course, be 
 remembered that the porus genitalis of this worm leads first into a 
 deep (O22 mm.) wide pouch or funnel-like cavity, which I have 
 called the " generative cloaca," because, besides the vas deferens, the 
 vagina also opens into its narrow posterior end. 
 
 The Cloaca originates by the external body- wall becoming swollen 
 into an annular lip round the common generative opening. In con- 
 sequence of this the pore comes to lie at the end of a sort of boss- 
 like protuberance, as in most of the other Cystotcenice, but here it is 
 unusually large, up to I mm. Transverse sections through the genera- 
 tive cloaca leave not the slightest doubt as to the nature of the swell- 
 ing. One sees not only (Fig. 144) how the cuticle is continued almost 
 unaltered into the interior, but can also follow the musculature of the 
 cortical layer out into the surrounding walls. 
 
 My former statements, according to which the pore was surrounded 
 by a special sphincter, which shut off the internal cavity during copu- 
 lation, have been corrected by Sommer and Landois. In reality one 
 sees in the wall of the generative cloaca no muscular elements other 
 than the processes of the transverse fibres bounding the inner layer, 
 which, instead of intertwining, run out to the outer surface of the 
 cirrhus-pouch, and sagittal fibres, which penetrate the projecting lips 
 in a dorso-ventral direction. But in spite of the absence of a proper 
 
STRUCTURE OF THE FEMALE ORGANS. 441 
 
 musculature, the generative cloaca is able to undergo manifold 
 changes in form and width, and thus to narrow or widen its opening. 
 These changes occur mainly in consequence of the pressure and trac- 
 tion of the adjacent body muscles. 
 
 We can the more rapidly dismiss the muscular structure of the 
 cirrhus-pouch, since it was especially Tcenia sayinata which we had 
 in view in our general account of this organ (p. 310). 
 
 The peripheral layer which the pouch possesses leads one to sup- 
 pose that it is in the cortical layer that the cirrhus-pouch has arisen. 
 This cannot indeed be demonstrated with certainty, since the above- 
 mentioned course of the transverse fibres obliterates the boundaries 
 between the two layers of the body. The nerve cord and the longi- 
 tudinal vessel, which are both distinctive of these layers, lie internally 
 to the cirrhus-pouch, but are divergent, inasmuch as they are not close 
 beside each other, but are approximated to different surfaces of the 
 body the longitudinal vessel towards that which we have formerly 
 called the "female," and the nerve cord towards the opposite or 
 "male" surface. The cirrhus-pouch is also more or less distinctly ap- 
 proximated to the latter, whether the pore be on the right or left side 
 of the body. 
 
 Although the situation of this pore varies extremely, lying always 
 on one side for perhaps six or eight joints, and then alternating 
 almost regularly throughout another series, yet there is on the whole 
 but little difference in this respect between the two sides. In a 
 length of 100 joints I counted 56 pores on the left, and 44 on the right. 
 
 Whether the pore lie right or left, one always finds it at some 
 distance behind the middle, and that the more markedly the longer 
 the joint. In isolated proglottides 12 mm. long, it lies fully 7 mm., 
 and sometimes even more, behind the anterior border. 
 
 The Female Organs. The narrow funnel-like end of the generative 
 cloaca contains not only the male opening with the copulatory organ, 
 but also, as we have seen, the female opening. This is so closely 
 approximated to the former, that the cirrhus can easily bend round 
 into it when the pore is closed. I have seen this take place in Tcenia 
 echinococcus and other species from the dog, and therefore I presume 
 it happens also in T. saginata. 1 The semen, thus introduced into 
 the female organs, first passes through the slightly enlarged terminal 
 portion into the vagina. This is a long and thin (0'025 mm.) canal, 
 which pursues for a while a straight course below the coiled vas 
 
 1 I have already (p. 310, note) mentioned that Somraer denies the entrance of the 
 cirrhus into the vagina, and asserts that the semen simply overflows into the female 
 opening without any true copulation. He thinks that I have been misled in my 
 observations by a stream of spermatozoa. 
 
442 GROWTH AND STRUCTURE OF T.EXIA SAGIXATA. 
 
 deferens, but bending downwards (Fig. 250) in a somewhat sharp 
 curve, ends in the middle line, half-way between the end of the uterus 
 and the posterior border of the joint. 
 
 Tlie Vagina, like the cirrhus and vas deferens, is lined by a con- 
 tinuation of the cuticle, but its walls possess considerable power of 
 resistance, and are thicker than those of the vas deferens, so that the 
 lumen measures scarcely more than O'OIS mm. It is plain, therefore, 
 that the vagina could not possibly receive and transmit the eggs, which, 
 even after the loss of the external envelope, are double the above- 
 mentioned diameter. We have, however, already noted that the eggs 
 of the Tteniadae only gain the exterior when the body-wall bursts 
 usually at the anterior border. 
 
 The Receptaculum Seminis, which is recognisable by its contents, 
 may be seen, just where the vagina reaches the posterior end of the 
 uterus, as a small swelling (Ol mm. long by 0*07 mm. broad). It may 
 be considered as occurring in the course of the vagina, although its 
 connection with the latter, both anteriorly and posteriorly, exhibits 
 several peculiarities. While the anterior portion of the vagina is 
 narrow and lined with chitin, perhaps to serve as a channel for the 
 transmission of the spermatozoa, the continuation posteriorly is wide 
 and thin- walled so different from the vagina proper, that we are 
 almost justified in regarding it as a special organ. Since it conducts 
 the spermatozoa to the ova, we have previously (p. 314) suggested 
 the designation " fertilising-canal " (*' Befruchtungs-canal ") as not 
 inappropriate for it. 
 
 The Shell-Gland. The canal just mentioned leads in its wide 
 course first to a spherical body about 0*2 mm. in diameter, which lies 
 some distance behind the uterus, in fact just where the vagina ends. 
 
 Even Mehlis 1 and Platner noticed this peculiar body, but had 
 only very imperfect knowledge of its nature and connections. Platner 
 took it for the ovary. As a matter of fact, the body in question 
 consists of closely compressed nucleated cells 0*02 mm. in size ; these 
 are, however, by no means eggs, but glandular cells, provided with 
 small thin ducts opening into the narrow internal cavity of the organ, 
 which measures O03 mm. The regular disposition of the cells and ducts 
 often gives the wall a radiate appearance. Since it is inside this 
 structure that the ovarian eggs acquire their outer envelopes of yolk 
 and shell, the shell-substance is probably the secretion of these 
 glandular cells. Since finding a body almost identical in structure 
 in the Distomidse, 2 I have called it the " shell-gland," a name often 
 used since by other observers. Sommer calls it " Mehlis' body." 
 
 1 Oken's 7*w, p. 70, 1831. 
 
 2 First German edition of this work, p. 483. 
 
THE SHELL AND GERM GLANDS. 
 
 443 
 
 It communicates further not only with the fertilising canal, but 
 also with the germarium and with the uterus, so that it is anatomically 
 a sort of centre of the female reproductive system. 
 
 FIG. 250. Sexual organs of Tcenia saginata (x 10). Male organs. 
 t., testes ; v.d., vas def erens ; c.p., cirrhus-pouch. Female organs. ov., 
 ovary ; y.g., yolk-gland ; m.b., shell-gland (Mehlis' body) ; r.s., receptaculum 
 seminis ; ut., uterus ; v., vagina ; g.p., genital papilla ; cl., cloaca. 
 
 The Germ-Glands consist, as usual in the Tseniadae, of a paired ovary 
 and an unpaired yolk-gland. The latter, the "albumen-gland" 1 of 
 Sommer, lies below the spherical body just described, near the posterior 
 border of the joint, and is in the form of a triangle, which has its obtuse 
 angle turned forwards, and extends some distance towards either side. 
 Sometimes the inferior margin is hollowed out or even interrupted, so 
 that it then appears almost double, as is shown in Fig. 142, represent- 
 ing Tcenia solium. But such appearances are neither normal nor yet 
 individual variations, as I was formerly inclined to suppose, 2 but are 
 artificially produced by unequal compression. 
 
 In contrast to the yolk-gland, the ovary has the form of two large 
 and almost round wing-like organs. They lie at either side of the 
 receptaculum seminis, but above the shell gland, and occupying more 
 than half the breadth of the remaining space (Fig. 250). Their height 
 is about the third part of the length of the joint. The space between 
 
 1 We have already (p. 320) given reasons for regarding this so-called "albumen- 
 gland " not as an organ occurring only in the Tseniadse, but as a form of yolk-gland widely 
 distributed among the Platyhelinintb.es. 
 
 2 I must again note (see p. 315, note) that in the first edition of this work I 
 erroneously regarded the yolk-gland as the ovary, and vice versa, as has been rightly 
 pointed out by Sommer. 
 
444 GROWTH AND STRUCTURE OF T/ENIA SAGINATA. 
 
 them serves for the reception of the lower end of both vagina and 
 uterus. About half-way up the wings are connected by a duct, which 
 runs across over the receptaculum seminis. That ovary, which lies 
 below the vagina, and is embraced by its curve, is always smaller 
 than its fellow, which is free to extend anteriorly, and reaches not 
 only beyond the vagina, but also beyond the vas deferens. 
 
 As to their minute structure, both ovary and yolk-gland consist of 
 a system of blind tubules, which, as in the so-called " tubular glands," 
 are seated on a branched efferent duct. I have never been able to 
 observe the reticulated communication which Sommer describes 
 between the tubules, and must say the same with regard to the coils, 
 with branches running backwards, which Platner has described in the 
 ovary (his " yolk-gland "). In teased preparations with low power one 
 may indeed see appearances of this sort, but closer examination shows 
 that the apparent network is composed of tubes lying across one 
 another. The ends of the glandular tubules are not unfrequently 
 widened into acini borne on thin stalks. This is specially true in 
 regard to the ovaries, which thus acquire a somewhat less dense 
 texture, and a more transparent appearance. 
 
 It is doubtful whether the bounding membrane of the tubules is 
 an independent skin, as in the testicular vesicles, or merely belongs 
 to the matrix. It is, at any rate, the only boundary of the glands. 
 The contents both of yolk-gland and ovary consist of cells about 0*007 
 mm. in size, with vesicular nuclei and distinct nucleoli. On the 
 whole, they resemble one another, but exhibit many differences on 
 closer inspection. 
 
 The cells of the ovary (the primitive eggs) have a sharper contour, 
 and are provided with a thin, clear, protoplasmic envelope ; they have 
 also a larger nucleus (the germinal vesicle), whilst the cells of the 
 yolk exhibit an abundance of a finely granular enveloping mass, not 
 
 unfrequently exceeding the above-mentioned 
 normal size. They are often very irregular 
 in form. Here and there the individual 
 cells are hardly distinguishable. They have 
 broken down and fused together into an 
 amorphous secretion, in which one can dis- 
 tinguish only a few flakes and nucleus-like 
 
 FIG. 251. Mehlis' body in structures, 
 connection with the various m , ,. , . ., 
 
 parts of the female productive The connection between these organs 
 organs, a. Efferent canal of the an( j the shell-gland can only rarely be seen 
 
 yolk -gland, b. Efferent canal . . ,. J . .. 
 
 of the ovary, c. Vagina and re- with any distinctness. Its demonstration is 
 ceptaculum,'d. Uterus. ( x 30.) the most difficult part of the anatomy. It is 
 most easily seen in the neighbourhood of the yolk -gland, for its efferent 
 
THE UTERUS AND ITS DEVELOPMENT. 445 
 
 canal runs straight forward and sinks into the posterior end of the 
 spherical body. It is much more difficult to demonstrate its connection 
 with the ovary. In favourable preparations, however, it can be seen 
 satisfactorily, and one can convince oneself that the efferent ducts of 
 the tubules finally collect into two transverse branches, which after 
 a short course meet together and then continue in a common duct, 
 which opens into the fertilising canal. Both transverse canals seem 
 to be very extensile ; they are often seen full of eggs, and sometimes 
 even enlarged into a distinct cavity. 1 
 
 The Uterus, however, is also in connection with the shell-gland, by 
 means of a thin duct (0*04 mm. wide), which springs from the gland 
 near the insertion of the fertilising canal, and opens into the posterior 
 end of the uterus. 2 The latter appears, in some respects, as though 
 it were the direct continuation of the canal just mentioned. Like it, 
 the uterus runs straight up the middle line of the joint, continuing 
 nearly to the anterior border, where it ends blindly. Of the subsequent 
 lateral branches there is as yet no trace. The uterus is still a simple 
 tube, with well-defined boundary walls and considerable width (up to 
 0'16 mrn.), so that it is sharply distinguished from the canal which 
 leads to it. The length of the latter is not always the same in the 
 different joints ; it is on the whole but short, so that the lower end of 
 the uterus usually projects some distance between the ovaries. 
 
 What I have just stated in regard to the structure of the sexual 
 organs in Tcenia saginata is primarily true only of the adult joints, 
 those, namely, which are about to copulate, and in which the filling 
 of the uterus is just about to commence. But a similar state of the 
 organs may be observed both in earlier and later stages, as was stated 
 with respect to Tcenia solium in the first edition of this work. In both 
 cases it is necessary to use the staining methods recommended above. 
 
 The Sexual Development is first apparent in joints about 2'5 mm. 
 broad by 0'3 mm. long, 3 which lie at a distance of about 6 to 10 cm. 
 behind the head, and belong to the first half of the third hundred. 
 In these joints there is seen passing from the centre to the middle of 
 
 1 For this reason they are regarded by Sommer, not as efferent canals, but as the 
 median portion of the ovary connecting the two lateral lobes. 
 
 2 Sommer, who confirms the above representation in all points, regards this canal, and 
 also the lower end of the fertilising canal, as a direct prolongation of the oviduct. He 
 gives them both the same name, and would thus have the lower end of the vagina (our 
 fertilising canal) not only opening into the oviduct, but would make the latter coil round 
 the shell-gland which is attached to it, and then run backwards to pass into the uterus. 
 I need hardly note that all these differences are only verbal, and I see little reason to 
 depart from what I have said, especially since the analogous structure in the Dis- 
 tomidae seems hardly to favour Somtner's theory. 
 
 3 I may again note that the accounts of the size and distance from the head are 
 rendered very uncertain by the extreme contractility possessed by these worms. 
 
446 
 
 GROWTH AND STRUCTURE OF T^)N T IA SAGINATA. 
 
 one side or the other a somewhat broad streak of cellular parenchyma. 
 At first (A) the stripe does not extend laterally beyond the median 
 region of the joint, but gradually it elongates until it finally abuts 
 
 FIG. 252. Development of the efferent generative organs in Tccnia saginata. 
 
 against the lateral. But before this (JB) the median end has thickened, 
 and become a posteriorly directed club-like swelling, which gives 
 the parenchymatous streak a certain resemblance to a pistol. The 
 contour, which was at first somewhat vague, and which made the 
 rudimentary structure look broad and plump, becomes more sharply 
 defined. As the joints increase in size, the length of the paren- 
 chymatous streak increases. It becomes more slender and changes 
 further ((7), since the terminal club-shaped body becomes almost 
 triangular, owing to the elevation of its anterior margin. Some 
 centimetres further on, about 100 joints after the appearance of the 
 first rudiment, this elevation has elongated into a streak, which can 
 be followed up to the anterior wall, and apparently represents the 
 first rudiment of the uterus. In the transverse streak, on the other 
 hand, we have neither the vas deferens merely, nor the vagina, but the 
 common rudiment of both these structures. This can be easily 
 proved, for the borders of the streak become gradually separated, as 
 two strands, by the clearing of the median portion and the thickening 
 of the borders, and these, though sometimes only imperfectly sepa- 
 rated, and still in connection with the mass of the uterus, may be 
 distinctly recognised as vas deferens and vagina. The former is at 
 first quite straight and destitute of a cirrhus-pouch, but that is no 
 more difficult to explain than the absence of the generative cloaca. 
 On the vagina there is sometimes no perceptible opening nor differ- 
 entiation into the various divisions, although the posterior end is 
 thickened like a club, and forms a swelling, which can be sharply dis- 
 tinguished from the adjacent parts of the uterus. 
 
 The next change in the generative organs is the disappearance of 
 the intermediate substance, which has as yet united the vagina and 
 vas deferens together. The two ducts thus become free, and develop 
 independently by the differentiation of the cirrhus-pouch and the 
 
SEXUAL DEVELOPMENT OF THE PROGLOTTIDES. 447 
 
 formation of the generative openings. In joints about 4*5 mm. broad 
 by 1 mm. long, which begin at about the fifth hundred, and are about 
 20 cm. distant from the head, one notices at the 
 end of the genital ducts a discoid swelling, which 
 encloses a shallow depression, and by its con- 
 nection with the vas deferens and vagina is seen 
 to be the genital papilla. The adjacent section 
 of the vas deferens exhibits a long thickening, 
 the first imperfect rudiment of the cirrhus- FIG. 253. Develop- 
 pouch. The coils of the vas deferens are hardly ent of the germ-produc- 
 
 t/ ing organs. (x5.) 
 
 perceptible, but the posterior end already 
 appears free, and without connection with the uterus, to which the 
 vagina is united by its terminal club-shaped swelling, both anteriorly 
 and posteriorly. Further, the uterus is now more sharply defined, is 
 more slender than before, and is usually prominent opposite the 
 generative ducts. 
 
 The first traces of the germ-producing organs are to be found about 
 the four hundredth joint. They are first indicated by the hitherto 
 almost homogeneous and transparent parenchyma assuming a more 
 granular appearance. The groups of cells of which this consists 
 are at first but small, and of the same appearance throughout, but 
 differently arranged in the upper and lower halves of the joints, 
 so that one can thus early distinguish the male and female organs. 
 In the following joints this distinction becomes more marked. The 
 granules of the upper half become larger, and are distributed with 
 tolerable uniformity over the whole surface of the middle region, 
 while those in the lower half remain smaller, and become ever more 
 distinctly arranged, so as to form distinct organs. In this way two 
 plate-like masses arise, which enclose the lower end of the vagina and 
 uterus between them, while very soon a third streak appears near the 
 hinder margin of the joint. These three masses of 
 course represent the two ovaries and the yolk-gland, 
 while the granules of the anterior half are destined to 
 become the testicular vesicles. 
 
 The joints in which one first sees the above 
 diferentiation distinctly are about the 420th behind 
 the head. In these one sees also for the first time that 
 the conducting apparatus are distinct canals, and Fl( *-254 Lower 
 
 ,.,.. , , -11 en< * f the vagina, 
 
 not solid threads. The vas deferens has a coiled Bowing its con- 
 course, and the posterior end of the vagina also nection with the 
 
 , ., . uterus, (x 30.) 
 
 exhibits its subsequent structure. One can recognise 
 
 already in the former terminal club (Fig. 254) a differentiation 
 
 into seminal vesicle and shell-gland, which for a time lie one close 
 
4-18 GROWTH AND STRUCTURE OF MXIA SAGINATA. 
 
 behind the other. The latter is seen to be in connection with the 
 lower end of the uterus. Similarly, one can distinguish the efferent 
 ducts of the ovary and the yolk-glands. 
 
 From this stage there is but a step to the perfect development 
 of the generative organs. All the parts are present ; the difference 
 is only formal, and the gradual development of the succeeding joints 
 requires no special discussion. 
 
 The development of the generative organs is not, however, com- 
 plete with the formation of the eggs and egg-glands ; for the Tcenice 
 are, as is well known, distinguished from the other Cestodes in that 
 they only produce eggs and spermatozoa during a comparatively short 
 time, and not merely are the eggs fertilised, but the embryos proceed at 
 once to develop in them. After the sexually mature joints there 
 follow others, which may be termed " pregnant," and this pregnancy 
 induces a further series of changes. 
 
 At the period of sexual maturity the uterus is a straight canal of 
 comparatively small calibre. Its capacity is too small for the great 
 multitude of eggs, and the more so since in the Tcenice the latter grow 
 during development to many times their original diameter. The 
 uterus therefore begins to adapt itself to the requirements of the 
 pregnant animal. Very soon after the transference of the first eggs 
 
 it not only increases in length, but entirely 
 changes its originally simple shape by the 
 formation of lateral branches. The walls 
 of the uterus give rise to small protube- 
 rances, which grow with ever-increasing 
 rapidity, here and there bifurcate, and form 
 secondary twigs, and finally fill up the 
 whole breadth of the median portion as far 
 as the longitudinal vessels. The branches 
 
 FIG. 255. Formation of the ,0^1 i ,- j j- 
 
 first lateral branches of the are at first long and thin, and differ from 
 uterus. (x5.) their subsequent state in being longer in 
 
 correspondence with the broad and short form of the joints, and also 
 in diverging but slightly from the transverse direction. 
 
 For a while the male and female reproductive organs can still be 
 seen beside the branches of the uterus. But the more the latter 
 increase, the more the former retreat from observation. This is not so 
 much because they are covered by the lateral branches, but is mainly 
 due to the gradual degeneration which ensues at the close of their 
 functional activity. This disappearance is gradual, and is not uniform, 
 so that even in a perfectly ripe joint, remains of the reproductive 
 organs may still persist. The female germ-producing organs persist 
 longest, and the shell-gland so long that the development of the 
 
STRUCTURE OF THE EGG. 449 
 
 posterior uterine branches is not only retarded for a while, but their 
 form is also somewhat modified by its presence. The vacant space 
 between the posterior fan-shaped processes represents the position 
 occupied by the shell-gland. The unequal longitudinal development 
 of the uterus posteriorly and anteriorly is also associated with the 
 persistence of the shell-gland. 
 
 B 
 
 FIG. 256. Eggs of Tcenia saginata; A, Newly formed egg from the 
 uterus ; B, Ripe egg containing the embryo. After a drawing by Edouard 
 van Beneden. ( x 550.) 
 
 As to the development of the eggs, I have but little to add to 
 what I have already said, which is partly based on investiga- 
 tions of Tcenia saginata. I content myself with noting that the size 
 of the embryo is about 0*02 mm. The shell which surrounds it is 
 distinguished by considerable thickness that is, length of the little 
 rods which are seated on it, and which attain their full development 
 after a very short period. Inclusive of this shell, the diameter of the 
 egg is on an average 0*03 mm., and its form is generally oval rather 
 than spherical. We have already noted that the eggs are also usually 
 still surrounded by the original vitelline membrane (0'07 mm.), 
 separated by an interval from the contents. Very frequently this 
 outer shell is drawn out at one or at two points into a more or less 
 long, thin, tail-like process, as is also frequently found in allied species. 
 This is still more constant in the newly formed uterine eggs, which 
 measure on an average 0*02 mm., and have usually a very distinct 
 oval form. The tails, which are almost as long as the eggs, always 
 spring from the poles. 
 
 Malformations. 
 
 There are but few tape-worms which exhibit such frequent and 
 various malformations as Tcenia saginata. Even the old observers 
 remarked some of them. But as at that time the two species of 
 large-jointed human tape-worms were not clearly distinguished, it 
 would be doubtful whether these observations referred to T. saginata, 
 
 2 F 
 
450 
 
 MALFORMATIONS OF TjEXIA SAGINATA. 
 
 or to Eudolphi's T. solium, were it not that the subsidiary circum- 
 stances mentioned in almost all cases prove that the reference is 
 to the former. My own observations of such malformations refer 
 almost exclusively to T. saginata, as do the researches of Leidy 
 and Welch, which we shall afterwards refer to. 1 Of course, this 
 does not imply that T. solium is by any means free from mal- 
 formations. 
 
 Of these different malformations, I will mention first that which 
 consists in the multiplication of the generative openings. This one is 
 by no means rare, and traces of it may be seen in almost every chain. 
 But, as a rule, the multiplication is but inconspicuous, and limited to 
 a few joints. Thus Pallas mentions joints with two or three genital 
 papillae, sometimes on the same side, sometimes on both sides, in ir- 
 regular alternation. Nor is this by any means the highest number. 
 I have myself counted five papilla? on one joint, and Colin 2 mentions 
 an unsegmented piece 15 cm. long, which must have possessed at 
 least 25-30 genital pores. 
 
 Especially interesting in this connection was a worm sent me by 
 Dr. A. Schmidt of Frankfort on the Main, in which there was a series 
 
 of such joints in various stages of develop- 
 ment. Closer examination showed, however, 
 that the malformation was not confined to 
 an increase in the number of generative open- 
 ings. Behind each porus genitalis there were 
 the component parts of a perfectly herma- 
 phrodite generative apparatus, as in the nor- 
 mal joints, except that the boundaries of the 
 various organs overlapped a good deal, and 
 
 . . . 
 
 nata with two and three genital that the various parts were not unfrequeiitly 
 
 im P erfectl y developed through want of 
 space. This was of course most distinct 
 in the younger unripe joints, where the uteri had not yet attained 
 their full development. When more than two openings are found 
 together in one joint, the sexual organs appertaining to the middle 
 pores are usually the least developed. The uterus is usually short- 
 ened, and has few lateral branches, and in the young joints the 
 female germ-producing organs are also small in size. Although the 
 shortening of the uteri is often very marked, and though the stems 
 and various branches of the different systems cross each other abun- 
 dantly, I have never seen them in direct connection. There were 
 
 1 Leidy, Proc. Acad. Philadelpk., p. 54, 1871 ; Welch, Quart. Journ. Alter. Sci. t 
 vol. xv., p. 1, 1875. 
 
 2 Gazette des Mpitaux, No. 1, 1876. 
 
 FIG. 257. Joints of T. sagi- 
 
MULTIPLE GENERATIVE PORES. 451 
 
 always as many isolated sets of sexual organs as there were gene- 
 rative openings. 1 
 
 This last fact shows sufficiently that in such cases as the above 
 we have not to deal with joints, as is apparently the case, but 
 with series of joints in which the separation of the individual 
 proglottides has not completely taken place. The slight indivi- 
 dualisation which we have already noted as characteristic of some 
 Cestodes, is here present as an abnormality it is true in 
 species which usually exhibit a very regular segmentation. Such 
 being the case, we can also understand the great length of the 
 joints with multiplied sexual openings, which may in some cases be 
 as much as 15 cm., as in Colin's piece, but the length of the joints 
 is not usually so great as one might infer from the number of 
 proglottides united, judging by their genital pores. The varying 
 degree in which these openings are approximated gives rise to many 
 differences. A portion of a worm with two genital openings had, for 
 example, a length of 18 rnm. instead of about 20, while another with 
 five was only 28 mm. long instead of about 50. 
 
 The case is quite different when two genital openings occur in a joint 
 opposite one another on the same level. Here one finds behind each 
 opening a set of male and female ducts, with cirrhus-pouch and vesi- 
 cula seminalis, but the reproductive organs proper are as usual, the 
 two vaginae passing into a common shell-gland, and into a single uterus. 
 
 As yet I have seen this malformation only twice 2 once in a joint 
 which was further abnormal, since the line of demarcation separating 
 it from the preceding joint could only be followed to about the middle. 
 
 Such an imperfect separation of neighbouring joints differs really 
 only in degree from fusion, and represents the incipi- 
 ent stage of the latter. This is proved by the fact 
 that the separation is in different cases unequal, the 
 demarcation-line protruding sometimes far into the 
 joint, but sometimes only to a slight distance from 
 the border. A complete absence of the line of demar- 
 
 FIG. 258. Double- 
 Cation IS, Of COUrse, a fusion. joint of a Tamia, 
 
 As usual, the slighter divergences are by far the with . tiir f e 8e3CUf ^ 
 
 f f . J openings (nat. size). 
 
 more common. This was alluded to in the remark 
 
 that almost every tape-worm exhibited examples of abnormal indivi- 
 
 dualisation. Sometimes these abnormalities occur repeatedly in the 
 
 1 I have never found the generative openings on the surface as Heller describes and 
 figures in such segments (Art. " Darmschmarotzer,"in v. Ziemssen's, " Handh. sp. Path, 
 u. Ther."Bd. vii., p. 601, 1875; transl. "Cyclop. Pract. Med.,"vol. vii., p. 716, 1877. 
 
 2 We have already noted (p. 419) that Tcenia vulgaris, Werner (T. dentata, Batsch), 
 is probably in reality a T. saginata which has repeatedly undergone this malformation. 
 
452 
 
 MALFORMATIONS OF TJUNIA SAGINATA. 
 
 same chain, as is the case also with the more marked divergences. 
 Especially interesting in this connection is the specimen observed and 
 drawn by Weinland, whose joints showed, as he says, an unusual 
 " tendency to bifurcation." 
 
 I need say little further regarding the structure of the generative 
 organs in these double joints. Each division has of course special 
 genitalia, as a rule quite perfectly developed, though their extremities 
 may perhaps be abnormally approximated. This is even better 
 marked in the case of the undivided side than of the divided, in 
 which, as a rule, the outer border possesses a greater length, and that 
 becomes the more marked the further the dividing line intrudes. In 
 the face of such facts, we cannot close our eyes to the presumption 
 that there is a certain connection between the growth in length 
 and the boundaries of the individual proglottides. 
 
 The greater length of the divided side also causes the furrow 
 separating the two parts of such a double joint to incline forwards in 
 
 a diagonal or curved line. Usually it 
 disappears sooner or later about the 
 middle, but it sometimes happens that it 
 extends to the anterior border. The 
 anterior half then acquires the form of 
 a superfluous joint, and this becomes 
 wedged-in on one side of the chain, be- 
 tween the divergent proglottides, as shown 
 by the first of the annexed figures (Fig. 
 259, A), which is taken from one of Dr. 
 Schmidt's preparations. The inner side 
 of the supernumerary joint was degene- 
 rated, as the wedge-like shape suggests. 
 The second figure (B) shows a very similar 
 appearance, which was reported to me a 
 long time ago by my late friend and 
 countryman Dr. Kriiger of Brunswick. 
 
 I must, however, leave it undetermined whether the explanation 
 here proposed be the right one or no. Moniez would prefer to deduce 
 the supernumerary wedge-shaped joint from reduplication at the 
 point of proliferation, and would therefore suppose that, instead of 
 one joint, two had formerly arisen beside one another. In the forma- 
 tion of such supernumerary joints he sees the beginning of the double 
 chains of Tcenia marginata (p. 398), which are distinguished by the 
 fact that the doubling of the point of proliferation persisted for a 
 longer time, and gave rise to a whole supernumerary chain instead bf 
 only to a single joint. 
 
 FIG. 259. Supernumerary joints 
 of Tcenia sayinata (nat. size). 
 
PRISMATIC TAPE-WORMS. 453 
 
 I may take this opportunity of mentioning that long since (in 
 1871) I heard from Dr. Pauli, of Frankfort, of a case which was cor- 
 roboratory of Moniez's opinion, in so far as it displayed a chain of 
 sexually mature proglottides, one of which bore a lateral chain com- 
 posed of two long narrow joints. But since the first joint of the main 
 stem was (according to the drawing, for I have not been able to 
 examine the preparation) scarcely broader than the first accessory 
 joint, it is quite possible that the case may be explained by the 
 assumption of a simple division. 
 
 With these double structures, the prismatic or triangular chains 
 we have previously mentioned may perhaps be associated. They 
 are, as we know (p. 396), formed from six-rayed heads, and may not 
 unfrequently be observed in Tcenia saginata. For the first mention 
 of them we are indebted to Bremser, 1 whose specimen is still pre- 
 served, according to Diesing, in the Imperial collection of Helminths 
 in Vienna. The worm consisted, according to Bremser, of two chains, 
 which were connected together throughout their entire length by one 
 lateral margin fastened to the other at a sharp angle. We have, un- 
 fortunately, no more exact description of the malformation, yet the 
 accompanying figure enables us to see that the two chains must have 
 been at approximately the same stage of development. The common 
 lateral border is projected into a sort of ridge bearing the generative 
 opening. Here and there another pore is present on another border. 
 Levacher 2 has observed a similar monstrosity, c 
 
 only that here the kind of connection was 
 different, in so far as that the one chain was 
 fixed to the other in the middle line. It is 
 doubtful whether the difference represents a 
 real fact, or is not merely verbal, especially 
 since the other cases the Tcenia lophosoma 
 of Cobbold, according to Kiichenmeister's 3 in- 
 vestigations, the case of Cullingworth and the 
 proglottides sent mej by Professor Auerbach 
 of Breslau (Fig. 260) are all closely related FIG. 260. Prismatic pro- 
 
 -r, , mi TT j. rn glottides (natural size). A, 
 
 to Bremser s worm. The Hottentot Tcema, | rom the v side . By fr ; om ^ 
 too, described and figured in the first edition front ; <?. from behind much 
 of Kiichenmeister's " Parasiten " has also been 
 
 shown by my investigations to belong to such forms, though the 
 author was at first inclined to regard it as a distinct species (Tcenia 
 
 1 Loc. cit., p. 107, tab. iii., Figs. 12 and 14. 
 
 2 Institut, p. 329, 1841. Comptes rendus, t. xiii., p. 661, 1841. 
 
 8 "Parasiten," 2d ed., pi. 6, Fig. 6. On Cullingworth's case see Med. Times and 
 Gaz., Dec. 1873. For Cobbold's paper, see Trans. Pathol. Soc., vol. xvii., p. 438, 1866. 
 
454 MALFORMATIONS OF T.-ENIA S AGIN ATA. 
 
 from the Cape of Good Hope). It exhibits the same connection 
 between the two chains, except that the one worm has a very much 
 smaller surface than the other, and seems hardly more than a longi- 
 tudinal ridge, resembling rather the common lateral border of the 
 Tcenia than the adherent wing. 
 
 This longitudinal ridge measured, in the ripe joints which 
 Kiichenmeister sent me, only 2 mm., while the adult second wing was 
 about 7 mm. broad. Yet it is the morphological equivalent of a whole 
 animal, as maybe inferred, not only from its participation in the segmen- 
 tation of the worm, but more cogently from the essential similarity of 
 its structure to that of the rest of the body. In thin transverse sections 
 one can see quite distinctly the characteristic cortical and middle 
 layers, both of which pass into the respective layers of the main body. 1 
 At the free border of the ridge there runs a longitudinal vessel, as 
 also on the free borders of the broad wing ; and a third wider one, 
 common to both borders, is situated where the ridge is attached. Out- 
 side the vessel the nerve may be observed. As to sexual organs in 
 the ridge, only testes were to be found, and these few in number. 
 Sexual openings were not perceptible there ; and even on the free lateral 
 border of the main body none of these could be found ; in the prepara- 
 tions examined they were always situated on the common border. In 
 regard to the connection, we must note that the median plane of the 
 ridge forms with the main body an angle of about 45, which is 
 open externally. Let us imagine the ridge to become broader, or what 
 comes to the same, to become more perfectly developed, then this 
 example would be quite identical with those described by Bremser or 
 Auerbach. 
 
 It is, of course, self-evident that, with the uniform development of 
 the two surfaces, the sexual organs will also attain a uniform develop- 
 ment. The proglottides sent to me by Auerbach, which were voided 
 by a boy three years old, who had harboured the worm for about one 
 and a half years, have enabled me to obtain a tolerably satisfactory 
 insight into the matter. 
 
 First, I would remark that the generative openings, as Auerbach 
 noted in his letters, and as Cobbold and Cullingworth asserted of 
 the worms observed by them, and as is seen in Bremser's figures, are 
 disposed throughout on one side, and are always found on the margin 
 common to the two wings. The alternation which Kiichenmeister 
 
 1 Kiichenmeister, who has since convinced himself of the fact of this arrangement, 
 appears to have overlooked my observations of twenty years ago, when he, by way of 
 proving that he has succeeded in making out the structure of the tape-worms in question, 
 appeals to his drawings, which "need no patronage whatever from the zoologists," 
 ( " Parasiten, " 2d ed., preface, p. iv). 
 
SEXUAL ORGANS OF THE PRISMATIC FORMS. 455 
 
 reports of his Tcenia from the Hottentot does not exist ; I have 
 reason to believe that the account was based upon error. Nor are 
 supernumerary pores ever observed on the lateral margins of the 
 wings. 
 
 The main stem of the uterus runs up the line where the two 
 wings are united to the ridge in a position which we must regard as 
 the morphological axis of the prismatic worm. It has through- 
 out the ordinary structure, and sends out numerous branches towards 
 the three angles, though these are indeed somewhat fewer than usual. 
 The longitudinal ridge which represents the somewhat less developed 
 median wing has the fewest and shortest branches. 
 
 But this longitudinal ridge is, as we have noted, the seat of the 
 generative openings, to which the ducts become subsequently con- 
 nected. I may omit the cirrhus-pouch and its contents ; they show as 
 few peculiarities as the generative cloaca. But it is otherwise with 
 the vas deferens, which, after issuing from the cirrhus-pouch, becomes 
 twisted together into a close coil of considerable size, which embraces 
 like a crescent one side of the longitudinal vessel running behind the 
 cirrhus, and then, still coiled, continues to the uterus, from which 
 it bends for some distance backwards. The 
 vagina lies on the same side, but is deeper, and 
 is turned more to the outside. It is difficult to 
 follow it posteriorly, but it is tolerably certain 
 that it gradually changes its original lateral 
 position for a median one, and runs backwards 
 at a short distance behind the longitudinal 
 vessel, between the latter and the coiled vas de- 
 ferens, or the uterus. The lower end, with the 
 receptaculum and the shell-gland, I have not been 
 able to see distinctly. But the ovary and yolk- 
 gland are present, and their lateral halves belong 
 to the two wings of the triangular joint, and to FIG. 261. Prismatic 
 that aspect which we called the female surface- Pgl>ttis in transverse 
 
 . -i t ,.-, . , . section through the porus 
 
 Ihe longitudinal ridge contains only the median genitalis. ( x8.) 
 portion of the germ-producing organs. The 
 numerous testes, filled like the vas deferens with semen, are embedded 
 in the interior surfaces of the two wings. 
 
 Besides the above-described prismatic proglottides, Professor 
 Auerbach also sent me three isolated joints of so strange a structure 
 that a close investigation was required in order to understand them. 
 
 On superficial inspection, they appeared as three-cornered de- 
 pressed cones or hollow pyramids about 8 mm. high, by as many 
 broad. The side walls had also the same size, and were united 
 
456 MALFORMATIONS OF T/ENIA SAGIXATA. 
 
 together by projecting ridges. At the point where they were fused, 
 at the apex of the pyramid or thereabouts, there were two sexual 
 papillae generally closely approximated. 
 
 At first sight these structures are, as we have said, extremely 
 puzzling, but on closer examination one becomes convinced that they 
 are proglottides in which the prismatic character is combined with a 
 multiplication of the generative papillae. They represent, in other 
 words, two imperfectly separated prismatic proglottides of asym- 
 metrical arrangement. 
 
 FIG. 262. Prismatic proglottides with double porus genitalis ; A -C from 
 the front, D ( = same specimen as O from behind (nat. size). 
 
 The three side walls, although superficially very like one another, 
 are in reality different, since two of them are halves of a sym- 
 metrical structure, like the two usual wings, while the third seems 
 to be a wedge-like piece which is intercalated into the triangular 
 space left by the posterior borders of the other two. We may then 
 explain the arrangement of the generative papillae by supposing that 
 one belongs to the lower end of the longitudinal ridge which runs 
 between the shortened wings, while the other is united to the 
 lower wedge-like portion which is always connected with one of the 
 wings, sometimes with the left and sometimes with the right. The 
 seam between these two parts denotes the anterior border of the wedge- 
 like piece, and the free border of the latter turned towards the other 
 wing is, in spite of its marked contraction, to be regarded as the 
 lateral border. This is in harmony with, the fact that the latter bears 
 the second genital papilla high up, close behind the longitudinal 
 ridge. This margin is succeeded by one inclined to it at an angle, 
 and directed somewhat laterally owing to its contraction, but repre- 
 senting the posterior border, as is proved by its projecting and everted 
 margin into which the succeeding joint fits. 
 
 Subsequently I found another proglottis which demonstrated the 
 truth of the above representation, inasmuch as it exhibited a stage 
 perfectly intermediate between the ordinary prismatic structure and 
 the one just described. It showed quite undeniably (Fig. 262, A) 
 the two ordinary lateral wings and the longitudinal ridge, but differed 
 in that the former were somewhat shorter than usual, and bore the 
 
PERFORATED TAPE-WORMS. 457 
 
 generative pore far down, and included between them posteriorly a 
 comparatively small and very narrow valve-like wedge. 
 
 Although the prismatic form of Tcenia saginata has been fre- 
 quently observed, no one has as yet had an opportunity of investi- 
 gating the head. Yet, from what we know of these malformations, 
 we cannot doubt that these cases are correlated with an unusual 
 structure of the head. As we have already noted (p. 396), it is the 
 six-rayed heads which produce such monstra per excessum. The three 
 angles represent the three radii, which are also expressed in the 
 suckers approximated in pairs. Where the ridges are unequally 
 developed, as in Kiichenmeister's Tcenia from the Cape, the position 
 of the suckers is probably also different. Perhaps the suckers belong- 
 ing to the reduced radius are unusually closely approximated, or are 
 represented by only one, as in the Tcenia with five suckers observed 
 by Gomez (according to Seeger). 
 
 Besides the above malformations, we must also note the forms 
 with perforated joints, the so-called Tcenia fenestrata (Tenia perce). 
 There are tape-worms, some of whose joints are normal, while others 
 are perforated by a larger or smaller hole (Fig. 263). According to 
 Bremser, this results from the rupture of the 
 uterus. The hole is at first small, and always on 
 the upper half of the joint, but sometimes in- 
 creases to such an extent that the greater part of 
 the worm is destroyed. I have in my possession 
 a piece a foot long, in which the median portion 
 has been wholly destroyed, and in which the joints 
 are held together only by their narrow margins, 
 and thus present the appearance of a rope-ladder 
 (Fig. 263, B). A second portion, belonging to 
 another worm, shows, among the 121 joints of FIG. 263. Series of 
 which it is composed, all the stages, from the J oints with perforated 
 
 i^ i , , proglottides (nat size). 
 
 nrst appearance of the perforation to complete 
 destruction (A). What I observe here leads me to doubt whether 
 the plausible explanation of Bremser 1 (who was by no means the 
 first to describe this malformation) be correct. This much at any 
 
 1 Masars de Cazeles (Roux Journ., t. xxix., p. 26), cited by Bremser, regarded 
 the perforated specimens as representative of a distinct species. The first to observe 
 these phenomena, so far as I know, was Goze, who, on p. 347 of his well-known work, 
 notes that, among the "dentate (' zackengliedrigen') worms" (i.e., Tcenia crassicollis, 
 auctt.), "there was one with perforated joints. Some joints had in the middle quad- 
 rangular holes, with delicate ramifications. The joints themselves were quite contracted 
 and deformed. The worm had probably suffered injury at this point, and was beginning 
 to repair it." Colin (Gaz. des k6p., No. 1, 1876) reports of a patient that some time after 
 the expulsion of T. fenestrata normal proglottides again made their appearance. 
 
458 CYSTIC STAGE OF T^ENIA SAGINATA. 
 
 rate is certain, that the perforation progresses from without inwards, 
 and gradually extends in depth as it increases in breadth. Here 
 and there the hole has two points of origin instead of one, but both 
 are in the anterior half of the joint. The superficial extension is 
 greater anteriorly, so that the posterior wall of the joint is in 
 extreme cases broader than the anterior. This circumstance seems 
 to be in some way associated with the special organization of the 
 sexual apparatus, but this connection can hardly be so simple as 
 Bremser would have it. This is evident enough from the fact that 
 the perforation is sometimes apparent in joints which are still far 
 from maturity. 
 
 The true nature of this abnormality perhaps rather a disease 
 than a malformation is still unknown. Even Kiichenmeister can 
 hardly be right in regarding it merely as the result of digestion. 
 The appearance of the worm, the smooth character of the sides of 
 the holes, and the duration of the malady, are difficult to harmonise 
 with this hypothesis. 
 
 The Bladder -Worm of Tieuia saginata and its Development. 
 
 Leuckart, "Die Parasiten des Menschen," Th. i., pp. 296-406 (first edition), 1863. 
 
 Having proved that the human intestine harbours not only Tcenia 
 solium, but a second large-jointed species of Tccnia, we are naturally 
 led to ask the question, How does this latter originate ? Kiichen- 
 meister at first (1855) believed that the young of the latter occurred 
 along with the ordinary bladder- worm of the pig, which had mean- 
 while been experimentally proved to belong to the life-cycle of 
 Tcenia solium, Eudolphi. In a communication made to the Academy 
 of Paris in I860, 1 he reports having actually found the young form of 
 T. saginata in the pig. The discovery has not, however, been con- 
 firmed, and the thrice repeated feeding experiments conducted by Dr. 
 Schmidt in Frankfort and by myself have yielded only a negative result. 
 
 But the result of this experiment is not the only argument against 
 Klichenmeister's supposition. The geographical distribution and 
 occurrence of Tcenia saginata point in another direction. 
 
 Specially instructive in this connection is the fact that the 
 Abyssinians, who are almost, without exception, from their earliest 
 years infested with Tcenia saginata, eat no swine's flesh, but, accord - 
 
 1 Comptes rendus, t. 1., p. 367. In the second edition of his work on parasites we 
 read (p. 199, note)" Since my preparation, which I held to be the Cysticercus of T. 
 mediocanellata, and which was taken from the pig, has been lost, I have no other means 
 of proof. This may be regarded by some as unsatisfactory, but I decline to quarrel 
 over it." 
 
 
FIRST EXPERIMENT ON A CALF. 459 
 
 ing to the reports of ancient and modern travellers, and particularly 
 of Davaine in 1860, owe the parasite to their use of the raw flesh 
 of sheep and oxen. This fact of course suggests that one of these 
 animals must be the intermediate host of this Tcenia, and that the 
 more certainly from the report of the army surgeon Knox, 1 who, 
 during the first Kaffir war in south Africa, witnessed the outbreak of 
 a tape-worm epidemic among the soldiers after they had fed for 
 a lengthened period on " overdriven and unsound " oxen. The South 
 African tape-worm proved from specimens sent me to be really Tcenia 
 saginata. 
 
 To this must be added a statement of "Weisse in St. Petersburg, 2 
 according to whom this common worm not unfrequently occurs in 
 children who have been fed on raw beef for dietetic reasons. This 
 result has been repeatedly confirmed in Germany, and the worm in 
 question is always T. saginata, as I first proved from the examination 
 of a case with which I was made acquainted through Dr. Harnier of 
 Cassel. The case mentioned was all the more interesting since it 
 concerned a Jewish child two years of age, belonging to a family in 
 Wlirzburg, who lived in strict observance of the law. 
 
 Guided by these considerations, I determined to experiment on 
 the ox at the earliest opportunity. Huber 3 and Schmidt had already 
 noted the probability of this animal being the intermediate host of 
 T. saginata. 4 * The latter spoke to me especially of a case where the 
 existence of the parasite could be traced with some certainty to the 
 eating of a meat salad made of raw beef. 
 
 The opportunity was soon forthcoming, thanks to the courtesy 
 and sympathy which I have so often experienced from Dr. Schmidt. 
 On the 13th November 1861, when the first edition of my work had 
 been for a long time in the printers' hands, I gave about a yard of 
 some eighty ripe joints of Tcenia saginata to a calf four weeks old, 
 and eight days later I repeated the feeding with a smaller dose. 
 
 The animal experimented on seemed so slightly affected by my 
 experiment, that I was about to extract a muscle, as I was wont to do 
 in such cases, when on the 9th December (i.e., twenty-five and 
 seventeen days after the first and second feedings respectively) my 
 
 1 Froriep's Notizen, p. 122, 1822. 
 
 2 Journal f. Kindtrkrankheiten, Bd. xvi., p. 384, 1857. 
 
 3 Bericht xiii. des naturhist. Vereins, Augsburg, p. 127, 1860. 
 
 4 Kiichenmeister claims priority in this supposition (" Parasiten," 2d ed., p. 149). 
 In the English translation of his text-book (p. 139), published in 1857, he says "The 
 fcolex was either seated in the beef or in mollusks, which might have been in the salad 
 or in the radishes." Apart from the fact that the association of beef and molluscs shows 
 how uncertain was his supposition, it must have been speedily abandoned, for we recall 
 his alleged discovery (in 1860) of the cystic form of Tcenia saginata in the flesh of the pig. 
 
460 CYSTIC STAGE OF MNIA SAGINATA. 
 
 servant brought me word that it had died during the night. The 
 day before it had been ill and unable to stand, though it had taken 
 its milk as usual. 
 
 An immediate post-mortem examination showed at once that the 
 feeding had been followed by a rich result. All the muscles, and 
 especially those of the breast and neck, and the psoas, were penetrated 
 by cysts, which had a breadth of T5-3 mm., and a length of about 
 2-4 mm. They were whitish, as if filled with chalky or tubercular 
 masses, such as had never been seen in the young cysts of Cysticercus 
 ccllulosce. Inside the exudation layer, which was surrounded by a 
 firm connective-tissue envelope, they contained a clear vesicle of 
 about 0-4-1-7 mm. in diameter. On cutting into the cyst this pro- 
 truded, and was recognisable as a young Cysticercus. 
 
 These bladder-worms were round, sometimes pointed at one pole. 
 The internal cavity was small, and mostly confined by the conical 
 
 vesicle to the distended end of the body. 
 Below the cuticle, which looked as if it 
 were continually shedding off scales, 
 could be distinguished first a thin layer 
 of delicate transverse and longitudinal 
 fibres (the first at intervals of 0*03, the 
 others of 0'05 mm.), whose muscular 
 nature was already evidenced by the 
 Fm. 264.-Young bladder-worms pow erful contractions of the little worm. 
 
 of Tcenia sagmata, with rudimentary *_ . . 
 
 head, (x 30.) Below this there was a thick layer of 
 
 small cells difficult to isolate, and finally, 
 
 clothing the internal cavity, large clear vesicles measuring 0'05-0'07 
 mm. in diameter. Between these there lay yellow balls of irregular 
 and partly ramified appearance. Vessels could not be detected even 
 in the largest bladder-worms, but the latter exhibited already the 
 rudiment of a head, which intruded for about 0*3 mm. into the 
 interior of the very wide bladder cavity, and which seemed to be 
 attached not to the equatorial zone, but to one end of the body. 
 There was as yet no trace of suckers. The interior of the head 
 showed hardly any terminal enlargement, but was in some of the 
 smaller bladder-worms still of a simple conical form. 
 
 Although these cysts were extremely numerous, and in many 
 places lay so thickly together that their total number must have been 
 many thousands, yet it seemed at first as if the death of the animal 
 under experiment could hardly have been caused by them. It was, 
 however, indeed the Cysticerci which had killed the calf. Further 
 examination showed that the distribution of the parasites was in no 
 way confined to the peripheral muscles of the body. The internal 
 
RESULTING PATHOLOGICAL CONDITIONS. 461 
 
 organs were also infested by immense numbers. The muscle of the 
 heart was penetrated throughout its whole extent by larger and smaller 
 cysts, as if with tubercles. The capsule of the kidneys was still more 
 strikingly altered, thousands of little white knots were intercalated 
 between the swollen lymph glands and reddened lymphatics. All 
 these little knots, in spite of their resemblance to tubercles, contained, 
 as we have noted, young Cysticer'ci. This crowd of cysts followed 
 the course of the swollen lymphatic vessels and glands into the 
 inguinal region. The smaller glands, rich in connective tissue, were 
 particularly infested by the cysts, while the larger, although swollen 
 in many cases to the size of a walnut, were almost free from them. 
 The lymphatics of the neck presented a very similar appearance, but 
 somewhat less striking, since there were fewer cysts. Swelling and 
 reddening were always present, so that the whole lymphatic system 
 (with the exception of the thoracic duct) exhibited an abnormal 
 appearance. Some of the glands were not only reddened, but were 
 also full of extravasated blood which penetrated throughout their 
 entire mass. Even under the skin these bloody patches were to be 
 found at various places, and were sometimes as large as beans. 
 
 Since the other viscera were comparatively, though not entirely, 
 free from Cysticerci (in the brain I found perhaps a dozen vesicles, 
 lying mostly free between the convolutions of the hemispheres) 
 I had almost no scruple in referring the death of the animal to the 
 pathological state of the lymphatics. The latter may also be traced 
 to the state of inflammation which resulted from the immigration 
 and development of such a number of parasites. 
 
 My respected colleagues, Professor Seitz and Dr. Hosier, to whom 
 I communicated this case, were of exactly the same opinion, and 
 remarked the resemblance between this case and acute miliary tuber- 
 culosis. 
 
 But whether death resulted from Helminthiasis, or from some 
 accidental complication, the experiment proved this much, that the 
 Cysticercus of Tcenia saginata inhabits the ox, and is developed not 
 only in the muscles, but also in the internal organs, and especially in 
 the lymphatics. 1 
 
 1 So I concluded in 1861, and so have all my successors concluded, except Kiichen- 
 meister, who, in the second edition of his work on Parasites (p. 152), writes as follows : 
 " Leuckart's first experiment, taken by itself, teaches us nothing, except that, after 
 abundant feeding with the proglottides of Tcenia mediocanettata, the animal remained long 
 apparently unhurt, till suddenly (twenty-five days after feeding) it died, and exhibited a 
 miliary tuberculosis caused by the Cestode brood. Without the subsequent experiments, I 
 cannot regard the first as of special value in regard to Tcenia mediocanellata." The accom-' 
 panying figures will perhaps convince Kuchenmeister that the first experiment was of some 
 importance in regard to the Cysticercus in question. The results I was able to draw from 
 that case are still almost the only ones forthcoming on this point. 
 
4G2 CYSTIC STAGE OF T.ENIA S AGIN ATA. 
 
 From the character of the bladders one could not help noticing that 
 they represented the early stages of a new Cysticcrcus, different from 
 the Cysticercus celluloses of the pig. 
 
 A second feeding experiment, which I began on the 27th December, 
 enabled me to supplement the results of the first. 
 
 Remembering the fatal issue of the former case, I used smaller 
 doses. First I gave twenty-five proglottides, and then several doses 
 of from five to eight at intervals of five or six days. After between 
 forty and fifty joints had thus been administered from two tape- 
 worms, voided soon after one another, the feeding process ceased. 
 Twenty days after the first infection many pathological phenomena 
 (loss of appetite, fatigue, ruffling of the hair, and fever) appeared, 
 which gradually increased to such an extent that I was for a while 
 afraid that the animal would not survive. Towards the middle of 
 the second week the disease diminished, till finally perfect health 
 returned. 
 
 Forty-eight days after the first, and thirty after the last feeding, I 
 extracted the sterno-mastoid muscle of the left side. Even during the 
 operation I observed, to my joy, the Cysticerci embedded among the 
 fibres. They had a somewhat oblong shape, and varied from 3 to 
 5 mm. in their longest diameter. Their appearance was still some- 
 what dull, but I saw the worm glimmering through the walls. It 
 was generally situated in the middle, whilst the ends of the cysts 
 were completely filled by the abundant granular cells and exudation- 
 granules. 
 
 In the extracted muscle I counted perhaps a dozen cysts, among 
 which there were some with wrinkled walls, and dead or disintegrated 
 inmates. 
 
 The worms without their shells measured between 2 and 3*6 mm. 
 in their longest diameter. The smaller specimens were almost all 
 spherical, while the larger already possessed a distinctly oblong form, 
 with diameters of 3*6 and 2 mm. Otherwise these parasites were like the 
 young tape-worms of the pig of the same age, and this to such a degree 
 that, without knowing the circumstances and without close examination, 
 the two forms might easily have been confused. In regard to the point 
 where the head is fixed there is at this period no difference, since the 
 head springs from the equatorial zone, instead of from the end of the 
 body, and is seen as a white opacity in the otherwise translucent wall 
 of the bladder. The previously divergent situation of the head sug- 
 gests an inference as to the phenomena of growth in the bladder-worms 
 of the muscles, and justifies the statement that their longest diameter 
 is by no means morphologically identical with the long diameter of 
 the other bladder-worms. 
 
FORM OF THE RUDIMENTARY HEAD. 4G3 
 
 The rudimentary head of the smallest bladder- worms appeared, on 
 close inspection, as a short cylinder 0'35 mm. across, and 0'6 mm. 
 long. The receptacle was always in close contact with the outer 
 surface. The sharp bend which is prominent in the Cysticercus cellu- 
 losce at a still earlier stage (p. 348) is not to be seen here, although 
 the cavity of the head is already considerably expanded at the lower 
 end, and the narrow neck is not unfrequently contracted into a coil. 
 I was struck by the presence of numerous small granules (0*007 mm.) 
 which filled the greater part of the cavity of the head (Fig. 265), and 
 by their firmness, resistance to chemical reagents, and optical charac- 
 ters, reminded me forcibly of the chitinous balls observed in the male 
 genital pouches of the young stages of Pentastomum. 1 The entrance 
 into the head-cavity formed a transverse slit, which crossed the 
 longest diameter of the body of the bladder-worm at right angles. 
 Bound about this slit several small calcareous bodies were to be seen. 
 The wall of the bladder was penetrated by a rich vascular network, 
 some branches of which passed into the insertion of the head, and were 
 continued into the substance of the latter. 
 
 FIG. 265. Head-rudiment of FIG. 266. Head -rudiment of 
 
 Cysticercus Tcenice saginatce before Cysticercus Teenies saginatce after 
 
 the development of the suckers. development of the suckers. ( x 
 
 (x 25.) 25.) 
 
 The larger bladder- worms of the extracted muscle were manifestly 
 older phases of the above. Their head-rudiment had grown with the 
 body to a size of 0*8-1 mm. The lower portion of the head-cavity had 
 enlarged to a spherical space of almost 0*5 mm. in diameter. The 
 pockets for the suckers were formed, and were almost all clad with 
 their muscular sheaths, though the disposition of the head was essen- 
 tially the same as before (Fig. 266). 
 
 What struck me most in regard to these bladder-worms was the 
 fact that they, although the descendants and young forms of a hook- 
 less tape-worm, were furnished with a distinct though small rostellum, 
 and with the rudiments of hooks. This was all the more striking, 
 
 1 Leuckart, "Bau und Entwickelungsgesch. d. Pentastomen, " p. 140 : Leipzig, 1860. 
 
4G4 CYSTIC STAGE OF T^ENIA SAGINATA. 
 
 since the occurrence of these structures in the adult tape -worms was 
 at that time all but unknown, for it was the prevailing opinion that 
 the complete absence of these structures was one of the most important 
 characters of Tcenia saginata. We have since learned that this is not 
 the case, and the above observation has thus lost much of its former im- 
 portance. But it is still of sufficient interest to claim our attention here. 
 
 The structure just mentioned consisted of a pit-like depression, or 
 of a diverticulum from the head-cavity. It lay between the suckers, 
 and therefore belonged to the apical surface. It reminded one much 
 of the cavity of a sucker, especially since it was similarly ensheathed 
 by a muscular layer, and was of almost the same size (0*25 mm.). 
 There could be no doubt as to its nature; it was a rostellum, a 
 structure therefore which afterwards remains abortive when compared 
 with the suckers, and is thus not to be found without difficulty in 
 the adult. 
 
 The anterior border of the apical pouch did not pass directly into 
 the cavity of the head, but was separated from it by an annular 
 diaphragm a structure which occurs at first in exactly the same way 
 in the hook-bearing bladder-worms (p. 351), but passes in the latter 
 forms ultimately into the apical lid (" Scheiteldecke "), into which the 
 basal roots of the hooks are fixed. The resemblance was all the 
 more striking since the border of the diaphragm was furnished with a 
 close circle of small points (O0035 mm.), just like those at first found 
 in the situation of the subsequent hooks in the armed forms. Here 
 and there these points were also present, deep down in the apical 
 cavity or in the suckers. 
 
 If the structure of this organ were not the same in all bladder- 
 worms (even in those with perfectly formed suckers), one might 
 suppose that a subsequent development into the ordinary structure of 
 the hook-bearing forms took place. The facts of the case, however, only 
 admit this hypothesis on the presumption that the chronological order of 
 the developmental processes in Tcenia saginata is different from that 
 observed in the other cystic tape-worms, in which, by the time the 
 suckers are fully developed, the metamorphosis of the hooks and 
 apical plate is also almost complete. But such a presumption was 
 not in any way justified by the condition of the adult Tcenia. 
 
 The calf experimented upon furnished material for definitely 
 investigating the development of this structure. This examination 
 was necessarily deferred for a time, so that the result might be indis- 
 putable. I therefore postponed the investigation for seven weeks, 
 until the bladder- worm might be reasonably supposed to have attained 
 maturity. One bladder-worm, which I cut out during this period 
 because it was visible through the skin of the under surface of the 
 
APPEARANCE OF THE INFECTED FLESH. 
 
 465 
 
 tongue, and was therefore easily accessible, exhibited hardly any note- 
 worthy change. 
 
 The appearance of the muscle three months after feeding was 
 exceedingly like that of measly pork. Oblong vesicles, with large 
 nuclei, were to be seen in great numbers, especially in the anterior 
 half of the trunk between the muscle-fibres (Fig. 267). Their length 
 varied from 4 to 8 mm., while their breadth was somewhat uniformly 
 3 mm. The head-rudiment had very considerably increased in size, 
 and formed a rounded appendage 1 to 1*3 mm. long by 07 to O9 mm. 
 broad. The organization of the head was, however, still unaltered. 
 Instead of a rostellum armed with hooks, the previous structure was 
 still present, except that the points had now disappeared on most of 
 the specimens. The neck not only contained a large number of 
 calcareous bodies, but was also much longer than before, and had con- 
 tracted into numerous close folds within the receptacle (Fig. 268). At 
 first very small when compared with the head, it now appeared as by 
 far the most conspicuous portion of the whole mass. The head was 
 confined to the lower end, and was not unfrequently much contracted 
 longitudinally, and displaced to one side, exhibiting many irregularities 
 in form and position. 
 
 ,!!!,, 
 
 FIG. 267. Cysticercus 
 Tcenice saginatce, em- 
 bedded in the muscle 
 (nat. size). 
 
 FIG. 268. Head-rudi- 
 ment of an adult Cysti- 
 ccrcus. ( x 12.) 
 
 FIG. 269. Cysticercus 
 with evaginated head. 
 (x3.) 
 
 The structure of the parasite becomes most evident when a 
 longitudinal section is taken through the head, or when it is protruded 
 by intentional pressure. In the latter case one notices at once a 
 wrinkled appendage about 3 or 4 mm. long, which has a somewhat 
 opaque appearance, due to the thickness of its walls and the abundance 
 of its calcareous corpuscles, and which runs forwards to the head and 
 the suckers. The latter organs have not yet attained their full size, 
 since they measure at most O35 to 0'4 mm., but they are markedly 
 larger than the suckers of Cysticercus cellulosce of the same age. On 
 the apex the head bears an opening about O14 mm. in diameter, 
 which leads into the cavity already mentioned, and, with the rostellum 
 just beneath, is to be regarded as a sort of frontal sucker, such as we 
 
 2G 
 
466 
 
 CYSTIC STAGE OF TffiNIA. SAGINATA. 
 
 have found in still more distinct form in other hookless Tseniadse 
 (Fig. 271). The size of this apparatus is hardly changed, so that it is 
 
 Fio. 271. Longitudinal section through 
 the head in situ. ( x 30. ) 
 
 FIG. 270. Evaginated head of Cyati- 
 cercus Tceniot sayinatce. ( x 30. ) 
 
 now much smaller than the lateral cups to which it was formerly equal. 
 Eound about the rostellum one notices as usual a vascular ring, into 
 which the four longitudinal vessels open (Fig. 270). Even the lateral 
 branches of the latter can sometimes be followed for some distance. 
 
 As to the distribution of the bladder-worms in the body of the 
 calf, I may remark that the large majority were found in the muscles. 
 After the muscles of the breast and neck those of the heart were 
 most infested, and specially those of the right ventricle. But the 
 greater number of the bladder-worms in the heart had perished 
 before their full development, as was evident from the dirty white 
 tubercular little masses (1-3 mm.) which shone through the serous 
 lining. Similar deposits were found in many other organs, especially 
 in the liver and the lungs, which also exhibited some adult bladder- 
 worms. Similarly in the thymus gland, the capsule of the kidney, and 
 in the brain. 
 
 The lymphatic system was quite normal, but in the inguinal 
 region, in Douglas' space and in other situations, numerous bluish-red 
 bodies, about the size of a pea and less, were to be noted, as in the 
 first animal. At many places the intestines were somewhat adherent 
 to one another, and also to the peritoneal lining of the body-cavity, 
 
REPEATED EXPERIMENTS ON THE CALF. 467 
 
 phenomena which clearly indicated an inflammatory state, appearing 
 as the result of the experiment. 
 
 I also succeeded in bringing the bladder-worms of Tcenia saginata 
 to development in the calf, and in watching the various stages up to 
 complete maturity. The hitherto often disputed distinctness of the 
 species was undeniably established, and one of the most important 
 sources of human food the ox was shown to be the intermediate 
 host of the most frequent and most widely distributed tape-worm. 
 At the same time it was experimentally established that the abundant 
 importation of tape-worm eggs containing embryos into the ox 
 occasioned a dangerous, and, under some circumstances, fatal disease, 
 which might, on anatomical grounds, be justly designated " acute 
 cestode tuberculosis." 
 
 Considering the enormous import of these facts to Helminthology, 
 hygiene, and pathology alike, it is not surprising that my experiment 
 was abundantly repeated by helminthologists, physicians, and espe- 
 cially by veterinarians. Similar investigations have been made on 
 several animals by Hosier (1864), Boll (1865), Gerlach (1869), Ziirn 
 (1871), Zenker (1872), Probstmayr (1879), and in England by Simonds 
 and Cobbold (1865 and 1866), in Belgium by the younger van Beneden 
 (1879), in France by St. Cyr (1873), as well as by Masse and 
 Pourquier (1877), and in Italy by Perroncito (1877). 
 
 With very few exceptions, these experiments yielded a positive 
 result. The exceptions include only an experiment made by Simonds 
 and Cobbold, 1 and a double experiment made by Klichenmeister, 
 Haubner, arid Leisering, which I do not count, since the maturity of 
 the proglottides was not ascertained, and since they were, in one case 
 at least, decidedly unripe. The calves or oxen under experiment all 
 became diseased with more or less striking, and often fatal, symptoms, 
 and exhibited on dissection numerous bladder-worms in the muscles, 
 and often in the viscera. These represented the results of the feeding 
 at various stages of development, but many of them were frequently 
 dead. They numbered usually many thousands, and in one case 
 where they had all perished at an early stage of development, they 
 were estimated by Simonds and Cobbold at about twelve millions. In . 
 this case, indeed, about four hundred proglottides had been given to 
 the animal within two months, which had, however, in spite of their 
 number, only a comparatively slight illness. 2 
 
 1 Kiichenmeister is mistaken in saying that Gerlach's experiment was without result 
 ("Parasiten," second edition, p. 153). See Bericht d. Thierarzneisch. Hannover, p. 70, 
 1869, where it is expressly noted that the calf, which was killed five months after feeding, 
 was "penetrated through and through with bladder- worms." 
 
 2 Journ. Linn. Soc. (Zool.), vol. ix., pp. 170, 1868. 
 
468 CYSTIC STAGE OF T.ENIA SAGIXATA. 
 
 The very reverse of this experiment is furnished by Zenker's case, l 
 in which a calf was fed with only a single proglottis whether full of 
 eggs or not is doubtful and remained in perfect health, yielding only 
 three bladder-worms in the muscles of the back. 
 
 To our knowledge of the structure and development of this blad- 
 der-worm all these observations have added but little. As far as 
 anatomical facts are concerned, they simply corroborate my former 
 statements. Only one point has been made clearer, and that by Ed. 
 van Beneden, who, as was formerly remarked (p. 360), was fortunate 
 enough 2 to observe numerous young Cysticerci still retaining their 
 embryonic hooks twenty-one days after feeding. In three cases he 
 was able to find all the six hooks, while in other cases only one or a 
 few were to be seen. A sketch he was kind enough to send me shows 
 the six hooks at some distance from one another, but yet still approxi- 
 mated in pairs, and at their original place of insertion by the side of 
 the rudimentary head, which had reached the stage shown in Fig. 
 264. In form, size, and histological structure, the young bladder- 
 worms had the greatest resemblance to the worms first observed by 
 me. Calcareous corpuscles and vessels were still absent. The heads 
 in many specimens were still indistinct, or in process of development. 
 Their place of formation did not appear quite constant, seeming some- 
 times to lie somewhat laterally instead of in the longitudinal axis of 
 the bladder. 
 
 We have, however, to thank the above investigators for important 
 results as to the pathological influence of these parasites. The 
 memoirs of Hosier, 3 Ziirn, 4 Simonds and Cobbold, and van Beneden, 
 are specially worthy of mention, because they have elucidated many 
 points with respect to the nature of acute cestode tuberculosis. 
 
 Zlirn's case has been perhaps most accurately followed in its 
 pathological bearings. A calf three months old, which had been fed 
 with fifty-seven ripe proglottides, exhibited symptoms of disease on 
 the fourth day after infection. The animal had a high temperature 
 (40 C., instead of 39'2) and a somewhat raised pulse, ate little, and 
 had an inflated belly, which was sensitive to touch. These symptoms 
 were probably caused by the wandering of the embryos, as is shown 
 by the fact that they disappeared after a short time, with the excep- 
 tion of pain which seemed to be felt when the walls of the belly 
 were pressed. A slight fever (with a temperature of 40'3) also per- 
 
 1 Sitzungsb. d. phys. med. Gescllsch. Erlanyen, Heft iv., pp. 71, 87, 1872. 
 
 2 The investigations referred to were communicated to me in manuscript by my esteemed 
 friend, and have since been published, Bull. Acad. Sci. Belyique, t. xlix., p. 659, 1880. 
 
 3 " Helminthologische Studien und Beobachtungen," pp.1-22 : Berlin, 1864. 
 
 * "Arbeiten der landwirthschaftl. Versuchsstation Jena," Zeitschr. f. Parasitcn- 
 kunde, Bd. i., p. 363, 1869. 
 
RESULTS OF POST MORTEM EXAMINATION. 469 
 
 sistcd. The other symptoms returned in greater intensity five days 
 later, i.e., nine after the feeding. From that time the fever increased, 
 until, on the seventeenth day, the temperature in the rectum reached 
 41 '8, the appetite also failed, the animal became feeble and declined, 
 lay much, and moved only with difficulty and pain. At last it could 
 hardly move without help, and was attacked by diarrhoea. On the 
 eighteenth day the temperature again began to fall. The animal was 
 quite unable to raise itself, the heart's action became gradually slower, 
 the respiration laboured, and four days later death ensued from failure 
 of the heart's action. 
 
 The results of post mortem examination are essentially the same 
 according to all investigators. The subcuticular connective tissue, in 
 many places, and especially where there are large lymph-glands, is 
 infiltrated by a serous fluid of a briny character. The muscles are of 
 a deep red colour, markedly injected, and in many places also exhibit 
 streaky exudations. They are further of a succulent consistency, and 
 are softened here and there, and penetrated by numerous cysts, 1 
 especially in the tongue, throat, neck, and breast. The heart is no 
 exception to this, but is often even more infested than the other 
 muscles, not only in its walls, but in its papillae and valves, and 
 below the endocardium. The circumference and bulk of the heart 
 are considerably increased. The same is true of the kidneys, and to a 
 less extent also of the liver. The viscera (with the exception of the 
 genitalia) are congested, the peritoneum is reddened, the lymphatics 
 much distended, the glands enlarged, and also to some extent altered 
 by extravasation of blood. The peritoneal and pleural cavities con- 
 tain a serous fluid. The membranes of the brain are very hyperaemic, 
 and the lateral ventricles distended, while the brain substance and the 
 pia mater exhibit a few extravasations. 
 
 The extent of the occurrence and distribution of the bladder- worms 
 in the internal organs varies greatly, and is sometimes only slight, 
 although the peritoneum and lymphatic apparatus are seldom quite 
 free from them. The kidneys, lungs, and liver contain on the whole 
 but few. Hosier saw some bladder-worms in the muscular layer of 
 the intestine, Perroncito 2 in the brain, and van Beneden in the sub- 
 cuticular connective tissue, and one example even in the vitreous body 
 of the eye, which lay in the centre of a bloody granular mass, some 
 millimetres in front of the retina. 
 
 The pathological changes which we have described vary, of course, 
 
 1 Van Beneden finds in these cysts, besides the granules and granular cells which I 
 mentioned, numerous free blood corpuscles. 
 
 2 " Esperimenti sulla produzione del Cysticercus della Taenia mediocanellata," p. 11 : 
 Torino, 1877. 
 
470 CYSTIC STAGE OF T^ENIA SAGIXATA. 
 
 greatly according to the intensity of the attack. The disease may, 
 indeed, assume another and perhaps less dangerous character. In 
 slight cases it is confined to insignificant and almost non-febrile dis- 
 orders of the digestive and locomotor functions. The animals lose 
 their appetite and liveliness, and grow thin, but in about 
 two months, according to Gerlach's case, or even sooner, according to 
 Simonds and Cobbold, return to the normal condition. If the disease 
 attain full development, it has, not only anatomically, but in its ex- 
 ternal symptoms, an unmistakeable resemblance to miliary tuber- 
 culosis, which results in a sort of typhoid fever. 
 
 In regard to the cause of death of the animals, very different 
 hypotheses have been advanced. I have expressed the opinion that it 
 is to be found in the derangement of the lymphatic system. This was 
 very pronounced in the first of my cases, and might perhaps be referred 
 to the irritation produced by the parasites which had migrated into the 
 lymphatics, and had there developed in large numbers. Although 
 this affection is, as a matter of fact, to be regarded as a constant 
 sign of acute miliary tuberculosis, Hosier thinks my explanation must 
 be rejected. He is of the opinion that death is due to the changes 
 occurring in the heart, which entail disturbances of the circulation 
 and associated dropsical exudations. And lastly, van Beneden regards 
 the death of the animal as the result of a whole series of pathological 
 processes. Besides the well-known alterations in the muscles, con- 
 nective tissue, and heart, he finds signs of peritonitis, and observes 
 clots of blood, not only in the right ventricle and in the left auricle, 
 but also at the bifurcation of the pulmonary artery, in the posterior 
 end of the aorta, and in the circle of Willis. These clots completely 
 close some of the vessels in question, and help to explain how, in the 
 final stages of the disorder, the posterior extremities of the animal 
 become paralysed and insensible. Although a bladder-worm has only 
 once been found in these thrombi, and then in the interior of one in 
 the heart, van Beneden thinks that they are in all cases to be referred 
 to parasites which have, somehow or other, passed into the vascular 
 apparatus, perhaps from the pericardium. He even thinks it possible 
 that the numerous extravasations of blood found in the animal had 
 been caused by migrating worms, and finally expresses the conviction 
 that the embryos pass into the blood-vessels at an early s'tage, and are 
 distributed throughout the body along with the blood. 
 
 But, however the question as to the cause of death may be settled, 
 this much is certain, that it is the ox that harbours the bladder-worm of 
 Taenia saginata, and conveys it to us in its flesh. 
 
 In view of this fact, it is further very surprising that the bladder- 
 worm from the ox, which cannot be very rare, from the frequency 
 
RARITY OF THE BLADDER- WORM. 471 
 
 of the associated tape-worm, only became known when its existence 
 was proved by my experiments. This is explained, however, when 
 we take into account the habits of the ox, and consider that it is 
 not only kept clean and carefully tended, but that, being entirely 
 a herbivorous animal, it has seldom opportunity to swallow large 
 masses of worms with the food which it takes in the open air. It 
 will, therefore, usually pick up only single proglottides, and, as we 
 learn from the result of Zenker's experiment, this would furnish, as 
 a rule, only few bladder-worms. The parasites are, moreover, distri- 
 buted over a large mass of flesh, so that they only occur separately, 
 and may be all the more easily overlooked, since, even in their adult 
 state, they are hardly ever larger than a pea. 
 
 But even since the discovery of the bladder-worms they have but 
 rarely come within the range of observation, at least in Germany and 
 the neighbouring countries. Siedamgrotzky once found one in Zurich, 
 in the muscle of the lip of a living ox; 1 and Gloss, in Frankfort, 
 proved its presence in a tongue, which (according to Heller) is still 
 preserved, partly in the collection of the Senkenberg Institute, and 
 partly in the Pathological Institution at Kiel. Guillebeau 2 has also 
 lately found another instance of the occurrence of the bladder-worm 
 in the tongue of an ox. 
 
 In other districts, bladder-worms from the muscle of the ox have 
 been more frequently observed. We learn, for example, from Knoch 3 
 that the St. Petersburg sausage manufacturers have long known them, 
 and that they describe them, in contrast to the pig bladder-worms, as 
 " dry, hard, and not so watery" a description which is in complete 
 harmony with the smaller size of the bladder, and the accumulation 
 of the " cheesy " enveloping substance. Knoch himself first observed 
 the bladder- worms in a cutlet, which came to table cooked, and it was 
 afterwards established, by his investigations, that the flesh of the cow 
 in question, which came from the neighbourhood of St. Petersburg, 
 was everywhere infested with cysts "of a dirty white colour, or 
 inclining to yellow." 4 According to the assurance of the vendor, the 
 newly cut meat had been inspected by the police medical inspector, 
 and pronounced faultless. As we are informed in the description, the 
 bladder- worms were, moreover, in very different stages ; for while some 
 were quite full grown, others had not even the rudiments of a head, 
 so that we are justified in concluding that there had been a repeated 
 
 1 Bericht d. naturf. Gesellsch. zu Zurich, Dec. 1869. 
 
 2 Mitth. nat. Gesellsch. Bern, p. 21, 1879. 
 
 3 St. Petersburg Medical Gazette, vol. x., p. 245, 1866 (Russian.) 
 
 * Hull. Acad. impe'r. St. Peter sbourg, t. xii., p. 347, 1867. While attempting to give 
 these opinions prominence rather than my own, I must say that there are many state- 
 ments and representations in the course of the essay which I am forced to reiect. 
 
472 CYSTIC STAGE OF T.ENIA SAGINATA. 
 
 and long-continued infection. The host of the adult tape-worm had 
 probably lived somewhere in the near neighbourhood of the cow. 
 
 In Algiers, where Tcenia saginata is very prevalent among Jews, 
 Mohammedans, and Christians, 1 the bladder- worm was repeatedly 
 observed by Chauvel in the diaphragm, and by Arnould in the loins. 
 This was also the case in Beyrout, where Talairach, a French naval 
 surgeon, found bladder-worms in the meat supply after a large per- 
 centage of the crew had become infected by eating beefsteak a 
 I'Anglaise.* 
 
 The frequency of the occurrence of the bladder-worm is of course 
 always determined by the conditions of infection, and these vary not 
 only according to the local circumstances and the abundance of the 
 tape-worm, but also according to the customs of the inhabitants and 
 their relations to the animal. This explains what has been lately 
 reported of the very wide distribution and extraordinary numbers of 
 this bladder-worm in Abyssinia and India, especially in the Punjaub, 
 where all these conditions are present. The most comprehensive 
 statements regarding this are those of the English physicians in India, 
 and especially Fleming and Lewis, 3 whose communications have 
 become widely known, owing to their publication in the English 
 Medical Journals, 4 and to Cobbold's summary of them. 5 As above 
 mentioned, the bladder-worm is especially common in the Punjaub, 
 where in 1869 not less than 768 out of 13,800 cattle were infected 
 (Cunningham), while in the previous year the per-centage was even 
 greater (6*12 per cent, instead of 5'5). Fleming mentions that during 
 the six years of his service there he hardly ever saw an ox or a cow 
 that was not infected with bladder-worms, although they were not 
 always confined to the muscles. Nor were they only found separately, 
 but sometimes in such numbers that Lewis counted in a pound of 
 flesh no fewer than 300 living Cysticerci. The flesh was taken from 
 the psoas muscle, for which and for the glutei the bladder- worms 
 seem, according to the Indian experience, to have a special preference. 
 The parasites were also often gathered together in larger or smaller 
 numbers at the root of the tongue, in which position some of them 
 attained a length of almost an inch. 
 
 This very frequent occurrence is accounted for when we learn 
 from the above-mentioned sources that the Indian oxen are not nearly 
 
 1 Ann. d. sci. not., t. xvii., Art. 15, 1873. 
 3 Mitn.. Acad. mtd., p. 998 : Paris, 1877. 
 
 3 The original papers are to be found chiefly in the Indian Medical Gazette, 1869, in 
 the Bombay Health Officers Keport, 1870, and in the Madras Monthly Journ. Med. Sci., 
 1873. 
 
 4 The Lancet, p. 860, 1872 ; The Veterinarian, p. 484, 1873. 
 
 "The Internal Parasites of our Domestic Animals,'" Chaps, iii., iv.,v. : London,1874. 
 
FILTHY HABITS OF THE ABYSSINTANS. 473 
 
 so exclusive in the choice of their food as our European horned cattle, 
 which are better kept and in cleaner stalls. Fleming has himself 
 seen oxen and sheep, as well as pigs, devouring human excreta with 
 great satisfaction. As the principal seats of the infection he rightly 
 regards the dirty pools and sloughs in the neighbourhood of the 
 Indian villages, where the manure of the district is collected, and 
 along with it the eggs and joints of the universally distributed tape- 
 worms. These are afterwards still more dispersed by the rain, and 
 carried into the cisterns, 1 the contents of which are always polluted 
 with excreta, so that the animals are infected by drinking as well as 
 by grazing. 
 
 The frequency and distribution of the bladder-worms from the ox 
 in Abyssinia seems to be due to very similar circumstances. This 
 I learn from a communication from Schimper to Al. Braun, which 
 lies before me in the original, but which, so far as I know, has not 
 yet been published. The bladder-worms are, he says, really forced 
 upon the ox by a very blameworthy practice of the inhabitants. 
 The Abyssinians, he continues, ease themselves in the open air, not 
 far from their dwellings, and indeed regularly at daybreak, in the 
 early grey of morning. At this time whole companies of them may 
 be seen daily cowering upon the ground in conversation. Their 
 clothing, which is like a white bed-cover, envelops the whole body 
 from the shoulders downwards, and also covers the spot on which 
 they sit. One thus perceives nothing of what is really taking place, 
 but only sees people cowering down at some distance from each other 
 and talking. To a stranger it seeins very surprising that every day 
 a company should assemble to talk at such an unusual hour in the 
 open air, and in the cold and damp of the morning; the real 
 business is still hidden from him ; and even afterwards he finds it 
 difficult to understand how the Abyssinians find it pleasanter to do 
 in company and for quarter of an hour what others do hurriedly and 
 in secret. After this matter is accomplished, the cattle are let out of 
 the shed. But they have to remain in the neighbourhood until the 
 bread for the herdsmen is baked and eaten. Only then are they 
 driven off to pasture. Meanwhile they remain in a place in which 
 millions of tape-worm eggs have just been deposited, many of which 
 have of course been transferred to grass and herbs and loose straw. 
 The cattle, eating these substances, swallow the eggs along with 
 them, and afterwards become infected with bladder-worms. 
 
 I must, however, expressly mention that Schimper had no know- 
 ledge of the investigations instituted in Europe regarding the con- 
 
 1 Dr. Oliver has also distinctly proved by microscopic investigation the presence of 
 tape-worm eggs in the cistern-water of the Punjaub. 
 
474 CYSTIC STAGE OF T/ENIA SAGINATA. 
 
 nection of Tcenia saginata with the bladder-worm of the ox, nor had 
 lie observed bladder-worms in the muscles of cattle. If, notwith- 
 standing this, he connects man and the ox in the way indicated, 
 he is supported not by the observations mentioned, but chiefly by 
 the fact that of all the domestic animals the ox holds by far the 
 most important place in the food of the Abyssinians. As pigs are 
 never reared nor eaten, only the sheep and the goat can be taken into 
 account besides the ox. But Schimper always found the goat free from 
 bladder- worms, although harbouring a tape-worm " whose proglottides 
 are similar to those found in man, and often occur in immense numbers 
 in the excreta." The sheep, it is true, is often infested in Abyssinia 
 by bladder- worms, but only in the liver (and in the hilly country also 
 in the brain) ; but these hepatic bladder-w,orms, which it is casually 
 remarked are longer than those found in the ox, and have " on the 
 two opposite sides a slender, membranous, wing-like structure," cannot 
 produce the human tape- worm, since the liver is not eaten, but thrown 
 away. On the other hand, Schimper thinks it very likely that the 
 tape-worm of the goat just mentioned is derived from these sheep 
 bladder-worms, especially as this animal might very easily become 
 infected with them. 
 
 Although Schimper expressly states that he always found the goat 
 free from bladder-worms in the muscles, and although two experiments 
 made by Ziirn and myself on this animal produced no positive results, 
 Zenker has succeeded in rearing 1 the bladder- worm of Tcenia saginata 
 in the goat. Twelve weeks after the feeding, Zenker found (besides 
 numerous compressed cheesy and calcareous bladder-worms in the 
 capsule of the kidney, liver, lungs, brain, heart, and muscles) two fully 
 developed living bladder-worms, regarding whose origin there could 
 be no doubt. On the other hand, however, these scanty results serve 
 to prove that the goat is but little adapted for the breeding of the 
 tape-worm. 
 
 All attempts to breed the parasites in other animals have failed. 
 Hosier, Cobbold, Zenker, and van Beneden experimented on the 
 pig just as unsuccessfully as Schmidt and I formerly did. Zlirn 
 fed a sheep 2 with Tcenia saginata, but it remained healthy and free 
 from bladder-worms, as I had formerly observed. In my case the 
 aninial had devoured about sixty ripe proglottides, and on post mortem 
 examination eight weeks later, the only alteration observed was the 
 presence of many small white dots in the liver, and a shrunken 
 appearance of the lymphatic glands of the groin and pelvis, which were 
 
 1 Loc. cit., p. 88, 1872. 
 
 2 The muscle bladder-worms which are now and then found in the sheep possess 
 hooks, and thus cannot belong to Tcenia saginata. 
 
SUPPOSED OCCURRENCE OF THE BLADDER-WOEM IN MAN. 475 
 
 also much infiltrated with blood. The same negative experiment was 
 made by Masse and Pourquier, 1 not only on lambs and sheep, but on 
 a rabbit and a dog. It was also made by Probstmayr 2 on a dog, and 
 by Heller 3 on rabbits, guinea-pigs, and apes. 
 
 The only animal, besides the ox and Zenker's goat, which has 
 hitherto exhibited the bladder-worm of Tcenia saginata is the giraffe 
 not the gazelle, as Klichenmeister asserts. Moebius found in the flesh 
 of one of these animals, in the zoological garden at Hamburg, abundant 
 specimens of this species. 4 It is very likely that the animal had 
 been infected in its home in the same way as the Abyssinian oxen. 
 
 From the danger which attends the migration and development of 
 these bladder-worms, we may regard it as a very fortunate circum- 
 stance that man is exempt from them. It is true that Heller 5 lately 
 stated that Colberg in Kiel identified a human bladder-worm (from 
 the eye) as the Cysticercus Tcenice saginatce, but, so far as I know, no 
 further details have been published on this point. So that until the 
 connection of the animal with the tape-worm is established by more 
 explicit statements, I think I am at liberty to doubt the correctness 
 of the diagnosis, especially as it is well known that there are bladder- 
 worms of Tcenia solium with stunted or even quite abortive hooks. 
 So much at least is certain, that if the bladder-worms of Tcenia 
 saginata were at all capable of development in man, many of them 
 would be found in the almost countless cases in which Cysticerci occur 
 in the brain and in the muscles. Their occurrence would probably be 
 even more frequent, since the risk of infection is much greater with 
 the constantly spontaneously liberated proglottides of Tcenia saginata 
 than in the case of T. solium. 
 
 How long the bladder- worm of T. saginata remains living in its 
 host cannot at present be decided. But we may reckon the length of 
 its stay there at several years, judging from its great resemblance in 
 occurrence, nature, and time of development to the ordinary bladder- 
 worm of the pig. The fact that the bladder-worms of T. saginata 
 (perhaps in connection with the lively reactions which they call forth 
 onHhe part of the host) are destroyed much more frequently and 
 in much greater numbers while young, than is the case with the 
 bladder- worms of the pig, can hardly allow any inference as to the 
 fate of tlie^survivors. Besides this, it appears as though it were 
 principally the bladder-worms in the viscera which are liable to 
 this destruction. 
 
 1 Ann. mtd. veUr. Biitxelles, 1876. 
 
 2 Jahrb. dcr Miinchner Thierarzneischule, 1869-70. 
 
 3 LOG. cit., Bd. vii., p. 602, 1875 (English transl., vol. vii., p. 718). 
 
 4 Zooloyischcr Garten, Bd. xii., p. 168, 1876. 
 
 5 Loc. cit., Bd. iii., p. 294 (Engl. transl., vol. iii., p. 556). 
 
476 OCCURRENCE AND MEDICINAL SIGNIFICANCE. 
 
 Occurrence and Medicinal Significance of Tsenia saginata. 
 
 Tcenia saginata belongs, like Ascaris lumbricoides and Oxyuris 
 vermicularis, to the cosmopolitan parasites. It is found wherever the 
 ox is domesticated, and wherever its flesh forms an important or 
 prominent article of food. The frequency of the tape-worm, of course, 
 varies very much acroiding to the countries and districts in which it 
 is found. It depends upon the presence of the bladder-worm, and 
 thus ultimately upon the keeping and care of the ox, as well as on 
 the preparation of the flesh. In places where this is done without 
 sufficient care, and the flesh is eaten perhaps in a half-cooked or raw 
 condition, the tape-worm is naturally of very common occurrence. If, 
 in addition to this custom, the cattle be negligently tended, and if 
 uncleanliness prevail in the stable yard and house, it is easy to under- 
 stand that both young and old, it matters not of what sex or station 
 in life, will be infested by these parasites. 
 
 Thus it was mentioned by Bruce, more than a century ago, that 
 the Abyssinians, whose morning occupation Schimper has so realisti- 
 cally described, eat raw flesh, and are consequently almost all infected 
 with tape-worm, and, as has already been noted, with Tcenia saginata. 1 
 Exceptions are extremely rare ; the worm appears even in children 
 of three or four, as soon as they begin, like their parents, to eat the 
 flesh "fresh and raw, and, if possible, still warm and quivering" 
 (Schimper). Even the Mohammedans and Europeans, who scorn to 
 live d I' Abyssinienne, are not entirely exempt from parasites, although 
 they are, of course, less exposed to them. Schimper himself was 
 attacked by them eight years after his settlement abroad. The 
 bladder -worms, or their heads, are distributed everywhere by the 
 universally prevailing uncleanliness, and the almost gipsy-like mode 
 of life of the inhabitants. Schimper conjectures that they are some- 
 times carried by flies. They adhere to table utensils to knives, 
 spoons, and plates and thus opportunities of infection are everywhere 
 afforded. And their distribution takes place all the more easily since 
 there are no sanitary commissions, no slaughter-houses, and no 
 butchers, but every one who wishes to eat flesh must kill the animal 
 upon his own premises. Only from <; a radical change in the degraded 
 social condition " does Schimper hope for any improvement. 
 
 Further, the Abyssinians do not regard the tape-worm as entirely 
 an evil. They maintain, on the contrary, and Schimper agrees with 
 them from his own experience, that without this guest they would be 
 
 1 This we learn not only from the descriptions given by Bilharz (Zeitschr. d. Gesellsch. 
 d. Aerztein Wien, I., No. 28, 1858), and by Schimper (in litt.), but from the investiga- 
 tions which Kiichenmeister made upon specimens sent by the former. 
 
EFFECTS OF THE PRESENCE OF THE TAPE- WORM. 477 
 
 unhealthy, arid that they would suffer especially from constipation 
 and its consequences. When the tape-worm is present, the stools are 
 somewhat fluid and uniform, thus imparting a greater power of resis- 
 tance against the rapid changes of temperature which prevail in a 
 mountainous country, and also decreasing the tendency to disease, 
 especially of an inflammatory nature. For this reason the Abyssinians 
 use cousso, not to expel the worm, which, in fact, it rarely does, but 
 only to shorten its length. As a rule they take, as Schimper re- 
 marks, a dose every two months, which at these intervals, has only 
 the effect of not allowing the worm to become so long as to be 
 troublesome to its host. The time at which it reaches this stage 
 varies, however, according to the diet of the individual. Those 
 who take little but good food are not troubled by the size of the 
 worm for a long time ; while others, and especially those who eat raw 
 flesh in excess, are afflicted by a remarkably rapid growth of the 
 parasite. When the worm is from 12 to 24 feet long, the expulsion 
 of the proglottides begins (Schimper), and from eight to twelve of 
 them come away daily. Now and then a pause occurs for some days, 
 although it may be assumed that the chain lengthens at the rate of 
 8 to 12 inches * in twenty-four hours. If the growth and expulsion 
 be proportionate, the worm excites no uneasiness ; but, as a rule, the 
 former preponderates, and thus it happens that the worm becomes 
 longer with age. It must not, however, be immediately concluded 
 that there is an insufficient expulsion merely because only a small 
 number of joints, or none at all, are separated ; for the separated joints 
 often remain in the intestine in larger or smaller numbers, until they 
 perish and disappear, and are ultimately voided in an unrecognisable 
 condition along with the excreta. 
 
 Abyssinia is, moreover, not the only country in Africa in which 
 Tcenia saginata occurs. We know that it is also found in Nubia, 
 Ethiopia, the Cape, Senegambia, Algiers, and Egypt. Thus it seems 
 to be pretty well distributed over the whole of Africa, and in many of 
 these countries is extremely frequent, though not so common, as in 
 Abyssinia. According to Primer, one can hardly open the body of a 
 negro without finding Tcenia lata (according to Bilharz, our T. 
 saginata). 
 
 In Asia we find a similar distribution and frequency. From the 
 above-mentioned reports of the English army surgeons, there can be 
 no doubt as to its occurrence in India, although no express mention 
 is made of it. It is particularly the Mussulman population of the 
 Punjaub that suffers from it, and especially in the lower classes, who 
 
 1 In the above-mentioned case of Perroncito, the average daily growth of the worm 
 amounted to 77 mm., that is to say, only about three inches. 
 
478 OCCURRENCE AND MEDICINAL SIGNIFICANCE. 
 
 have a custom of eating half-done beef; and in the English regiments 
 stationed there, Tcenia saginata is of frequent occurrence, inasmuch 
 as some of the soldiers adopt the same practice. In one case the 
 disease broke out three months after the march, and indeed not in a 
 few, but in from fifteen to twenty cases. After two years' residence, 
 about a third part of the soldiers were infected with the tape- worm. 
 Only the officers, whose food consists principally of mutton, which is 
 also prepared in a cleanlier and more careful way, are, as a rule, 
 exempt. The Hindus are still more free from it, since they live 
 entirely upon vegetables. 
 
 In respect of frequency of occurrence, Arabia and Syria are little 
 behind India. This is shown, for example, by the fact already men- 
 tioned, that a French naval ship stationed off the Syrian coast, whose 
 crew had procured their supply of beef from the shore, and had 
 devoured much of it in the form of beef-steaks d la Tartare, had, 
 after a short time, a considerable number of cases of tape-worm 
 (19 out of 152 men). 1 We also learn from Kaschin that among the 
 Buratis inhabiting Baikal every individual is infected with a tape- 
 worm. 2 It is true that these observations were not made on the 
 spot, but in Irkutsk, where the individuals in question were all men 
 who had been garrisoned for years as Cossacks. But in spite of the 
 great distance from their home, they were nearly all infected with 
 tape-worm, a and sometimes with several (up to fifteen), which 
 Kaschin took for Tcenia solium, but which undoubtedly belonged to 
 T. saginata. This is seen not only by the description which Kaschin 
 gives of the worm (20 feet long), but from what he tells us of the 
 habits of their hosts. We learn, for instance, that the Buratis live 
 almost entirely upon flesh, especially on that of oxen, sheep, camels, 
 horses, and more rarely of pigs, and that they are so voracious that 
 two men are able to devour at one sitting a sheep two years old. 
 Moreover, this flesh is neither perfectly cleaned nor even cooked, and 
 is eaten from a table which has been used immediately before in 
 cutting up the slaughtered animal, and which has as little acquain- 
 tance with water as the vessels and their owners. Fat, liver, and 
 kidneys are eaten raw, and sick animals are as little despised as 
 half-rotten carcases. 
 
 Schmidtmuller observed Tcenia saginata (Bothriocephalus tropicus) 
 in Java, principally, it is true, but not exclusively, in the black 
 soldiers imported thither from the coasts of Guinea ; and Professor 
 
 1 Mem. A cad. mtd. Paris, p. 998, 1877. 
 
 2 St. Petersburg Medical Gazette, vol. i., p. 366, 1861 (Russian). 
 
 8 In 113 post mortem examinations the worms were only twice absent, and their 
 presence was also proved in 500 other persons who were treated in the hospital. 
 
GEOGRAPHICAL DISTRIBUTION. 479 
 
 Balz writes to me from Tokio, that it often occurs in Japan, and is 
 much more frequent than T. solium. The case seems to be the same 
 in China, at least many of the French soldiers 
 returned from the Palikao expedition infected 
 with this worm. Fedschenko also found the worm 
 to be widely spread in Central Asia. 
 
 Eegarding Australia and America, the com- 
 munications are more scanty, but it is known with 
 certainty that this species is not wanting there. It 
 was also identified by Kiichenmeister and myself FIG. 272. Ripe seg- 
 
 . -p. ., , i JL. . , , T ., j -XT -n ment of T(Knia saginata. 
 
 from Brazil, and by Weinland, Leidy, and Vernll var. aUetina ; after 
 in North America. Weinland, among others, Weinland - ( x 2.) 
 observed it in a Chippeway Indian, but in a form which was very 
 markedly distinguished from the typical Tcenia saginata by the small 
 size of its proglottides, and by its slender form, so that he was almost 
 tempted to regard it as a separate species. 1 He constituted it a 
 variety abietina, and relying upon the branching of the uterus, classed 
 it along with T. solium, erroneously, however, as may be seen from 
 the drawing of the preparation he kindly sent me (Fig. 272). 
 
 In Europe hardly a country can be mentioned in which Tcenia 
 saginata has not been found. In fact it is the predominant species 
 of tape-worm in the south and south-west, in Bavaria, Austria, 
 Hungary, Italy, and Turkey. In the north of Germany and in 
 Denmark it has also, during the last twenty years, gradually forced 
 the formerly more frequent T. solium into the back-ground. While 
 the cases of T. saginata had to be counted by units at the time of the 
 appearance of the first edition of this work, it is now, on the contrary, 
 T. solium that has to be sought for. It has become rare, since its 
 relations to the bladder-worm of the pig have become known to an 
 ever-extending circle, and since the fear of Trichina has taught us to 
 pay greater attention to the condition of meat. 
 
 We possess, however, but few statistics of a definite nature. In 
 Copenhagen, where, until 1869, the relation of Tcenia solium to 
 T. saginata was as 53 to 37, Krabbe afterwards found only 16 
 examples of T. solium among 62 large-jointed tape-worms. Accord- 
 ing to Grassi, 16 examples of T. saginata were found among 19 
 large-jointed Tee-nice in Milan, and according to Marchi, 34 out of 
 35 in Florence. Similarly all the tape-worms investigated by Bremser 
 in Vienna were, with one exception, hookless, and as this one came 
 
 1 I have, however, no intention of denying that besides the species of the " common 
 human tape-worm," with which we are acquainted, there may be here and there some 
 new ones which are still unknown to us. But there are certainly fewer with us than 
 with the nomadic, hunting and pastoral peoples beyond the bounds of Europe. 
 
480 OCCURRENCE AND MEDICINAL SIGNIFICANCE. 
 
 from a military hospital, its origin was extremely doubtful. Bremser 
 was at first even inclined to doubt the existence of any hooks in 
 T. solium, for which the Vienna tape-worms were taken, until 
 Eudolphi sent him from Berlin the drawing of an armed human 
 tape-worm. 1 
 
 Still more insufficient are the data which have any bearing on the 
 frequency of Tcenia saginata in Germany and the neighbouring states, 
 since in them the two large-jointed species are almost always associ- 
 ated together. But it may at least be gathered from them that the 
 occurrence of the tape-worm varies in different districts, but that it 
 nowhere attains the frequency with which we have seen it to occur in 
 certain parts of Africa and Asia. 
 
 According to the generalisations of the French army surgeons, the 
 tape-worm is twenty-three times as frequent among the soldiers in 
 Algiers as in France. On the ground of these statements, Davaine 
 reckons that in France hardly one tape-worm occurs among 8200 
 inhabitants, but adds that this number would be too small for Paris. 2 
 This proportion is also too small for England, as is shown, for instance, 
 by the fact that Bateman, a physician in extensive practice in London, 
 found among every 543 patients one infected with tape-worm. On 
 the basis of results obtained in the Dresden and Erlangen hospitals, 
 Miiller reckons, among 3814 post mortem examinations, twenty-four 
 cases of tape-worm (nineteen Tcenia solium, five T. saginata) ; that is 
 to say, 1/168, or about 0*63 per cent., and these were so divided that 
 about 013 per cent, were cases of T. saginata, and about 0*50 per cent, 
 of T. solium. It is, however, a moot-point whether this per-centage 
 ought to be regarded, without further investigation, as a standard for 
 the whole population. In Thuringia, according to da Conta, there is 
 one tape- worm patient in every 3315 inhabitants, and in the medical 
 districts of Eisenach, Apolda, Jena, and Weimar, where swine are 
 abundantly reared, and Tcenia solium is presumably the more frequent, 
 there is one in every 486. In the town of Hanover the tape-worm 
 patients have been reckoned even at 2 per cent. 3 
 
 The variations in the per-centages representing the occurrence of 
 tape-worms (and therefore also of Tcenia saginata) are of course deter- 
 mined by certain local circumstances which are dependent upon the 
 conditions of infection already discussed. These circumstances also 
 enable us to understand how certain classes and occupations suffer 
 
 1 Loc. cit., p. 101. Klichenmeister indeed holds another opinion, for according to him 
 Rudolphi found hooks in a worm sent to him by Bremser as bookless. In consequence 
 of this incorrect version, an unmerited slight is cast on Bremser's credibility. 
 
 2 Loc. cit., t. ii., p. 83. 
 
 3 Compare p. 151, note. 
 
CONDITIONS INFLUENCING LIABILITY TO INFECTION. 481 
 
 much more frequently from tape-worms than others. It has for 
 example long been known that the female sex is much more fre- 
 quently infected than the male ; and further, that cooks, butchers, and 
 tavern-keepers, in short all those people who have to do with the 
 preparation of animal food, furnish an important contingent of tape- 
 worm patients. This is very well shown by the calculations made by 
 Wawruch. 1 Among 173 tape-worm patients, who (since the Observa- 
 tions were made in Vienna) must have suffered mostly from Tcenia 
 saginata, he found no fewer than thirty-nine cooks, twenty-six maid- 
 servants, and thirteen innkeepers, butlers, and butchers. This does 
 not take into account the large number of housewives, who, as Waw- 
 ruch's patients belonged chiefly to the lower and middle classes, must 
 have been very generally busied in the kitchen. The proportion of 
 the female tape-worm hosts to the male was almost 2:1 (117:56). 
 Most of the patients were in middle life (between twenty-five and 
 fifty), when there is, as a rule, a great relish for flesh. 
 
 The fact that in the present conditions of European life any oppor- 
 tunity for the acquisition of the tape-worm is, on the whole, somewhat 
 rare, is due mainly to the circumstance that Tcenia saginata occurs as 
 a rule singly, unlike T. solium, whose larval forms, as we have seen, 
 are much more frequently associated than those of the related species. 
 To this fact the former owes its designation " Ver solitaire," which is 
 found so far back as Andry, and was all the more used by the French 
 physicians, since, in consequence of an etymology which we have seen 
 to be erroneous (p. 411), the epithet "solium" was also applied to the 
 solitary worm. On the other hand, the very general use of the name 
 in France shows that the tape-worm indigenous to that country is 
 principally T. saginata.' 2 ' 
 
 But sometimes two or three, or even more ; examples of Tcenia 
 saginata are found in the same intestine, 3 as has been often observed, 
 and is shown, for example, by the fact that Wawruch's 173 patients 
 harboured altogether 206 worms. Of course such great numbers as are 
 found in the Buratis (fifteen specimens in one intestine) can hardly 
 ever occur with us. 
 
 From our present knowledge of the life-history and mode of 
 transmission of these parasites, it need not surprise us that, in 
 some cases, several members of the same family suffer at the same 
 
 1 " Praktische Monographic der Bandwurmkrankheit : " Vienna, 1874. 
 
 2 Indeed I have in two cases identified tape-worms procured in France (Paris and 
 Nice) with the above. 
 
 3 From Kiichennieister's work (p. 192) I extract the fact that the Tubingen Patho- 
 logical Institute possesses four examples of T. saginata from one intestine, and that Dr. 
 Pfaff in Zittau also expelled seven from one patient at one time. 
 
 211 
 
482 OCCURRENCE AND MEDICINAL SIGNIFICANCE. 
 
 time from Tcenia, or that the disease sometimes assumes an epidemic 
 character. * 
 
 If it be asked in what way the transmission of the worms takes 
 place, the general answer is, that it is effected by the eating of raw or 
 under done beef. At least this is the rule, for we hardly need to con- 
 sider the cases in which infection may have been caused by the goat, or 
 the giraffe, or even by the sheep (for in spite of the above-mentioned 
 negative results, the latter is, perhaps, like the goat, capable of rearing 
 bladder- worms). 
 
 The important share that the eating of raw flesh has in 
 determining the occurrence of the worm, has already been shown 
 by the large number of cooks and maid- servants infected with 
 tape-worm, regarding whom it may be added that if they would eat 
 the flesh in the same manner as their superiors, without tasting it 
 beforehand, they would probably hardly have to suffer in any greater 
 proportion. We must also notice the fact which, since Weisse's 
 day, has been often observed, that this parasite is very frequent in 
 persons, young or old, who from dietetic reasons have been fed on 
 raw beef. 2 
 
 It is not, however, only in raw flesh that the bladder-worm is 
 transmitted to the future host, but also in meat in a half-cooked 
 condition, which appears not unfrequently upon our tables in the 
 form of roast beef and beef-steak d I Anylaise. I know defi- 
 nitely, for instance, of one case, in which the Tccnia saginata origi- 
 nated from a beef-steak, which the host, a colleague now dead, 
 had eaten in Nice. Besides the dishes just mentioned, all those 
 should be deemed suspicious in which the flesh and blood are 
 almost or altogether of their original condition and colour. Only 
 well-cooked, thoroughly boiled or roasted, flesh sufficiently insures us 
 against infection. 
 
 Kegarding the effect produced on the bladder- worm by the method- 
 ical application of a higher temperature, we have, thanks especially to 
 the investigations of Perroncito, a series of interesting conclusions. 3 
 We learn for example that the motions of the worm, which at a low 
 temperature (up to about 30 C.) were very slight or altogether 
 absent, became extremely lively at 36-38, but afterwards subsided, and 
 at 44 almost entirely ceased. At 45 C. death ensued, as was shown 
 
 1 For cases of this kind see Davaine, loc. cit., second edition, p. 100. I mf*y also refer 
 to the observation of Knox already mentioned (p. 459). 
 
 2 This is the case not merely in Germany, but also in France and Italy ; see for 
 example Levi, " Delia frequenza della taenia per 1'uso medico della carne di manzo cruda," 
 (riornale Vcncto di sci. med., vol. i., p. 169, 1876. 
 
 3 " Della grandine o panicatura," Torino, 1877, and especially " Esperimenti sulla pro- 
 duzione della Tsenia mediocanellata, " &c., Torino, 1877. 
 
TENACITY OF LIFE OF THE BLADDER- WOEM. 483 
 
 not merely by the turbid appearance of the bladder-worms, but per- 
 haps still more convincingly by the fact that when swallowed (in 
 three cases) they were found to have no effect. 
 
 The bladder-worms survived the death of their host only fourteen 
 days (in March) ; for after the expiration of this time (and sooner in 
 the parts more exposed to putrefaction, such as the tongue), the para- 
 sites were all found to be dead. If abundantly sprinkled with water, 
 or dipped in it, they perished in twenty-four hours. A solution of 
 common salt had the same effect, so that the supposition that salt 
 meat might sometimes cause infection with Tcenia saginata seems 
 somewhat doubtful. Further, the usual way of preparing beef in Italy 
 has at least the effect of completely killing the bladder-worms. A 
 case is mentioned by Perroncito of forty-six persons (ten families, 
 including children and adults, men and women) who twice ate bladder- 
 worms in flesh prepared in the national way, and yet without any 
 individual becoming infected with tape-worm. 
 
 On the other hand, a student of Perroncito's who had swallowed a 
 newly extracted living Cysticercus, saw the first proglottides leave him 
 fifty-four days later. Fourteen days afterwards he voided, in conse- 
 quence of an anthelminthic which he had taken, a Tcenia saginata of 
 427*4 cm., the number of whose joints was estimated (from below 
 the neck) at 866. 
 
 The experiment just mentioned is, however, neither the first nor 
 the only one, directly proving the development of the bladder -worm 
 into Tcenia saginata. Oliver, an Indian army surgeon, had previously 
 subjected a Mohammedan and a Hindu boy to the same experiment, 
 and, twelve weeks after the swallowing of the bladder-worm, obtained 
 from both the proglottides of Tcenia saginata. 
 
 It is thus clearly shown by the foregoing observations, the only 
 ones that state with any definiteness the term of the infection 
 that from nine to twelve weeks must elapse before the Tcenia saginata 
 gives off the first proglottides. The regeneration will, of course, take 
 a longer or shorter time, in proportion to the size of the remaining 
 neck. If the head be left behind, we generally expect that proglot- 
 tides will be again voided, in two to two and a half months after the 
 first expulsion. Cobbold reports a case in which medicine was ad- 
 ministered three times in succession, whose first application had the 
 effect of expelling a stretch of joints 14 feet in length. On being 
 repeated ten weeks later, 16 feet were voided, and a third dose, nine 
 weeks after the second exit of proglottides, evacuated a stretch of 
 17 feet. Schimper estimates the average number of proglottides 
 voided in one day at eight to twelve, but this varies greatly, and is 
 often not so large (p. 477). The exit of a larger number (Kiichen- 
 
484 OCCURRENCE AND MEDICINAL SIGNIFICANCE. 
 
 meister speaks of from fifteen to twenty) ought always to be taken as 
 an indication of the presence of several worms. 
 
 Attempts to rear the adult worm in animals have hitherto failed. 
 So far as I know, however, these experiments are confined to the case 
 of a dog. During three days, this animal ate hundreds of bladder- 
 worms, but four hours after the last meal, nothing was found but some 
 heads in the stomach and beginning of the small intestine. 
 
 The life of the present species seems often to be very long. At 
 any rate it is not at all rare for the patients to evacuate proglottides 
 almost daily for years. One of my Eussian students harboured two 
 tape-worms for more than five years. In another case the disease 
 continued for more than eight years. 1 Wawruch mentions several 
 cases which lasted from twenty to twenty-five years, and in one case 
 speaks even of thirty-five years. Of course it is doubtful whether 
 this is always the effect of the same tape-worm. If, in a disease that 
 is apparently of long standing, the evacuation of the proglottides cease 
 for months and even for years, and then suddenly begin again, we 
 may safely conclude that the infection has been repeated. Several 
 cases of this kind are recorded by Davaine. 8 
 
 Regarding the death of the tape-worm we know of course even 
 less. But it is very probable that after its death, which of course 
 always severs the former adhesion, it is generally expelled pretty 
 quickly along with the other contents of the intestine, and 
 without undergoing much alteration in form or condition. If it 
 remain longer in the intestine, it may. like the retained proglottis 
 mentioned by Schimper, gradually undergo maceration, and then be 
 ejected in a hardly recognisable mass. In rare cases a kind of 
 mummification takes place. The problematical body which Pro- 
 fessor Aitken found in the intestine of a soldier, and gave to 
 Cobbold, who mentions it in his work on Helminths, 3 was nothing 
 else than a mummified Toenia saginata, which I could clearly identify 
 from some pieces which were sent me for closer investigation. In 
 addition to this case, Kiichenmeister has recently recorded a mum- 
 mified * Tcenia, observed by Ziirn and Meyer, which was voided by 
 a strong man suffering from a violent attack of colic. Owing to the 
 kindness of my honoured colleague, I have been able to examine 
 the latter more closely, and have also made the accompanying sketch 
 of it. Like Cobbold's preparation, it appeared to be a nearly cylin- 
 
 1 Cobbold knows many cases in which the patient had suffered from tape-worm for 
 five, six, ten, or even eleven years, and had voided proglottides uninterruptedly. See 
 " Worms : a Series of Lectures on Practical Helminthology," Lect. 4 to 8 : London, 1872. 
 
 2 Loc. cit., second edition, p. 102. 
 
 3 "Entozoa," p. 415 : London, 1864. 
 * "Parusiten," second edition, p. 96. 
 
USUAL SITUATION OF THE WOEM. 485 
 
 drical body, almost like a long and thick thread of pretty firm texture, 
 and with wrinkles and cracks, some of which ran transversely, but most 
 of them in a longitudinal direction. These were partly destroyed by 
 soaking, and then one saw a distinct segmentation, whose 
 traces, when once discovered, were easily observable. The ex- 
 istence of eggs containing embryos in the interior has been 
 already noted by earlier observers. They have lost their 
 spherical form, and by the constriction of one segment have 
 assumed an almost hour-glass shape, as may be not unfre- 
 quently observed, 1 if, by the application of strong spirit or 
 otherwise, the water is suddenly withdrawn from them. The 
 small length of the joints and the slender form of the 
 mummified worm, which are much more striking than in 
 Cobbold's case, lead me, however, to suppose that in Ziirn's 
 case the parasite was not Tcenia saginata, but T. solium. 
 
 The normal abode of the tape-worm is the small intes- FlG - ?7 3 -r~ 
 
 ~Pipf*p t'of : 5 a 
 
 tine, to the walls of which it is fixed, usually towards the mummified 
 upper end. As may be assumed from analogy to related ta P e , worm 
 forms, the head is usually sunk in the villi of the intes- 
 tine, and covered by them. "When in possession of its full vital 
 powers, the worm hangs so firmly that it is necessary to pull and 
 bend it before it will quit its hold. And even after it has done 
 so, it will attach itself again in a moment, if the head succeed in 
 catching hold of a portion of the intestine. Those who only know the 
 worm in its expelled condition can with difficulty form any proper 
 idea of the vital energy and mobility which it exhibits in its normal 
 condition, in the warm intestine of its host. The serpent-like motion 
 and powerful peristalsis of the jointed body, the continuous manifold 
 play of the suckers, and the bendings of the neck, are all phenomena 
 of which those who have seen the worm only in a cold and motionless 
 condition can have no idea. 
 
 The tape-worm hangs from its point of attachment in the direction 
 of the stream of chyle, and generally close by the wall, so that its 
 whole length extends backwards within the alimentary canal. As a 
 rule it is straight, but more rarely it exhibits serpentine windings or 
 coils, according to the varying state of contraction of the different 
 parts. Pruner found in one corpse five Tcenice of considerable size, 2 
 which extended throughout the whole length of the small intestine ; 
 and Eobin saw one tape-worm which hung through the end of the 
 small intestine into the large intestine, although its point of insertion 
 lay high up near the pylorus, and although its anterior end was rolled 
 
 1 Leuckarfc, " Blasenbandwiirmer," p. 95. 
 
 2 "Krankheiten des Orients," p. 245. 
 
486 OCCURRENCE AND MEDICINAL SIGNIFICANCE. 
 
 into a coil as large as an apple. 1 Sometimes it even happens that the 
 end of the tape- worm protrudes from the anus during defecation, and 
 on any attempt to remove it (as Andry has observed), quickly with- 
 draws again into the intestine (p. 425, note). The knots which are 
 sometimes observed on the thin anterior body of expelled worms, can 
 hardly be regarded as normal structures, since they probably arise 
 only from the unusual cramp-like contractions, caused by the use of 
 anthelminthic medicines. 
 
 If the stream of chyle turn in consequence of powerful anti- 
 peristalsis (especially in vomiting), the position of the tape-worm in 
 the alimentary canal may be occasionally reversed that is to say, the 
 posterior end may be turned forwards. Cases are known in which the 
 whole or portions of the tape- worm have been vomited, 2 and in one 
 case forty yards are said to have been ejected in this way (van 
 Doeveren). Lavalette, a French physician, has lately reported the 
 case of a pregnant woman who expelled the proglottides singly 
 through the mouth. 8 
 
 Where abnormal openings occur in the alimentary canal, like the 
 so-called frecal or intestinal fistulse, the proglottides, and even whole 
 worms, occasionally find an exit through them (Richter, Spoering). 
 We are even informed of an instance in which the tape-worms broke 
 through the wall of the abdomen through a newly formed abscess, 4 
 so that it almost appeared as though the worm had caused the forma- 
 tion of the abscess, although the nature of the tape- worm body hardly 
 permits us to suppose that it could bore through the intestine, if the 
 latter had not been already in a diseased condition. 5 Especially in- 
 teresting, in this connection, is a case mentioned by Herz, in which 
 the tape- worm (whether it was Tcenia saginata is, of course, uncertain) 
 issued through the navel, without, however, bringing any of the con- 
 tents of the intestine along with it, so that the patient could be dis- 
 missed as cured a few days after the exit of the worm. 
 
 Of a similar nature are the rare cases in which the tape-worm was 
 expelled through the urethra. In such cases, even when the ordinary 
 signs of vesico-rectal fistula are wanting, it is evident that the worm 
 can only have reached the urinary apparatus from the intestine. In 
 one of the three cases mentioned by Davaine, the tape-worm remained 
 
 1 Journ. de med., t. xxv., p. 222, 1766. 
 
 2 See the cases collected by Davaine, loc. cit., p. 100. 
 8 Quoted by Davaine, loc. cit. 
 
 * Ibid., p. 114. 
 
 8 Like Goze and other observers, I have repeatedly found Tcenia pectinata living free 
 in the body-cavity of the rabbit, but have never succeeded in finding any wound in the 
 intestine. 
 
 6 Med. Zeitung des Vereins fur HeiVcunde in Prcussen, p. 75, 1843. 
 
EFFECT OX THE HEALTH OF THE HOST. 4-87 
 
 a year in the bladder, and expelled single proglottides at intervals of 
 about eight days, until it was killed by an injected anthelminthic and 
 then expelled at once. 1 We need hardly add that the expulsion of 
 proglottides through the urethra is accompanied by violent and painful 
 disorders, and that the above-mentioned worm-abscesses interfere in 
 many ways with the health of the host. 
 
 Besides these, the presence of a tape-worm in the intestine gives 
 rise, under some circumstances, to protracted disease. I say " under 
 some circumstances," for in many cases the health remains unim- 
 paired in spite of the uninvited guest. This happens especially in the 
 case of young children and healthy persons, while, on the other 
 hand, and particularly where there are previous nutritive disturbances 
 and nervous irritability, many and various diseases may be caused by 
 the parasite. As a rule, however, there is an exaggerated fear of the 
 pain excited by the tape-worm. There are some whose complaints 
 begin the moment that they discover the presence of the parasite, 
 although they have perhaps harboured it for months ; and others who, 
 after having undergone a tape- worm cure, continue to feel their former 
 pains, although, perhaps, they have long been rid of the worm. 
 Just as physicians speak of a " hypochondriasis syphiliticorum" there 
 often seems even more occasion to diagnose a " hypochondriasis tcenio- 
 sorum" 2 We have already noted that, in contrast to the disfavour 
 with which we regard the worm, the Abyssinians consider themselves 
 ill when they are without it, and regard it as having an advantageous 
 influence on their health. Only if it become too long do they think 
 that it causes any disorder. 
 
 In Europe, too, it is sometimes asserted that the tape-worm 
 has a medicinal value. This idea is, however, erroneous ; for in 
 cases in which Tcenice of the dog (especially T. marginata) occurred 
 in the alimentary canal of the host, I have not unfrequently observed 
 a diseased condition of the intestinal mucous membrane (injection, 
 desquamation of the epithelial layer, and even little ulcers), and, as I 
 have already observed, there could be no doubt that these were due 
 to the parasite. 
 
 The disorders usually caused by the tape- worm are partly local 
 and partly of a general nature. And among the former, besides the 
 troublesome and disagreeable tickling occasioned by the spontaneous 
 emigration of the proglottides, we find frequently recurrent disturb- 
 ances of digestion and colic-like pains, which are felt sometimes at 
 one place and sometimes at another, especially during fasting, being 
 quieted for a time by food and drink. Sometimes the patients have 
 
 1 Darbon, Archiv. de Med., t. v., p. 351, 1824. 
 
 2 For such cases see Cobbold, "Worms, &c.," p. 14. 
 
488 1VEXIA SOLIUM, RUDOLPHI. 
 
 also a feeling as though the worms were heaving up and down inside 
 the intestine. And indeed it is quite conceivable that the powerful 
 contractions of Tcenia saginata have an influence on the condition of 
 the intestine. The projecting borders of the joints thus rub in a file- 
 like manner over the villi, and easily produce a congested state, which 
 lasts a longer or shorter time according to circumstances, and gives rise 
 to many diseased symptoms. Moreover, diarrhcetic stools rarely con- 
 tinue in tape-worm patients, and there is often, on the contrary, an 
 irregular alternation of diarrhoea and constipation. 
 
 If the disease continue long the nutrition suffers. From this 
 there often arises a condition which has a certain resemblance to 
 anaemia, and which especially exhibits the many neurotic symptoms 
 of this disease. Singing in the ears, hallucinations, giddiness, fainting, 
 pains in the joints, epilepsy, chorea, and even mental diseases, have all 
 been observed to be caused by the tape-worm, and not unfrequently 
 to disappear on the removal of the latter. 1 
 
 It is easy to see, however, that these cases, although so numerous, 
 contain little that is characteristic. They might arise from other 
 causes as well as from the tape-worm. A certain diagnosis is there- 
 fore impossible. To this end one must observe eggs or proglottides 
 of the corpus delicti, and these must always be identified, before so 
 radical a cure as treatment with anthelminthics is begun. 
 
 b. Cystic Tape- Worms with Circlet of Hooks. 
 
 (Cystotaenia, sensu stricto.) 
 Taenia solium, Eudolphi. 
 
 Gtfze, " Eingeweidewurmer," p. 269 (T. cucurbitina plana, pellucida). 
 Kuchenmeister, ' Ueber Cestoden," p. 85. 
 Weinland, " Essay on the Tape- worms of Man," p. 32. 
 
 In size, thickness, and number of segments, this species is considerably 
 less than the last. In its extended condition, the length rarely amounts to 
 more than from 3 to 3'5 metres, and in preserved specimens it is generally 
 less than 2 metres. The greatest breadth, which is attained about 
 the middle of the body, hardly ever exceeds 8 mm. The number of the 
 segments may be estimated at about 850, and of these not more than 80- 
 100 are ripe proglottides. These make up a third of the whole length, 
 and at the end of the chain attain a length of 10-12 mm., and a breadth 
 of 5 mm. The head is about the, size of a pin-head, and has a spherical 
 shape with somewhat prominent suckers. The, apex is not unfrequently 
 
 1 For further information regarding the diseases of tape-worm hosts, and an account 
 of a number of interesting cases, see Davaine, loc. cit., p. 101. 
 
DEFINITION OF T^NIA SOLIUM. 
 
 489 
 
 coloured by a black pigment, and bears a medium-sized rostellum, with 
 generally twenty-six or twenty-eight hooks, which are distinguished from 
 those of the allied species Toy their compressed and rather stout form, 
 and by the relative shortness of their roots. Following the head there 
 is a thread-like neck, a centimetre in length, whose segmentation cannot 
 be easily detected by the naked eye. The first segments are extremely 
 short, ~but those succeeding gradually increase in length, so gradually, 
 however, that they only assume the rectangular form at a distance of 1 
 metre, en* even more behind the head. More posteriorly, the ripe segments 
 begin, the sexual organs having been fully developed about 200 joints 
 anteriorly, or at about the 450th joint. The ripe proglottides are only 
 rarely spontaneously voided, and generally find an exit, singly or in 
 numbers, along with the excreta. The sexual opening is situated behind 
 the middle of the joint. The uterus, which is generally seen distinctly 
 through the envelopes of the body, has seven to ten lateral branches, which 
 are separated from each other by considerable distances, and in their 
 turn again divide into a number of dendritic or comb-like branches. 
 The eggs are almost round and are enclosed in a firm shell, whose outside 
 is covered with thickly set little rods. Sometimes the original clear egg- 
 membrane persists within the shell. 
 
 FIG. 274. Head 
 of Tcenia solium. 
 (x 45.) 
 
 FIG. 275. Half- 
 ripe and ripe joint 
 of T. solium (nat. 
 size). 
 
 FIG. 276. Two 
 proglottides of T. 
 solium with uterus, 
 (x 2.) 
 
 The corresponding bladder-worm (Cysticercus cellulosae) has a special 
 preference for the muscles of the pig, but is occasionally found in other 
 
490 HISTORY OF CYSTICEKCUS CELLULOSE. 
 
 places and in other animals, as in man. Its occurrence, in the pig at 
 least, is usually 'very abundant. The caudal bladder is of moderate size 
 (8-10 mm.), and in the muscles has an elliptical form, the longest diameter 
 being in the direction of the course of the fibres. It contains a spirally 
 rolled and much wrinkled head-process. 
 
 The species which we have just attempted to characterise, and 
 have designated by Linne"s name Tcenia solium, is by no means identi- 
 cal, as we have already seen, with the similarly named species of the 
 former helminthologists. " The common human tape-worm," to which 
 they gave this name, is a collective species, which includes both 
 Rudolphi's hook-bearing Tcenia solium and the hookless T. saginata. 
 Although both species are even yet frequently included in one, especi- 
 ally in foreign countries, we do not require to prove, after the fore- 
 going discussion of the history and peculiarities of T. saginata, that it 
 is justifiable and even necessary to regard them as two markedly 
 distinct species. The size, armature, uterine structure, and develop- 
 ment exhibit such characteristic features in either species that a 
 union of the two is impossible. It is especially the mode of develop- 
 ment which decides the matter, for it shows that the differences of 
 structure which were formerly supposed to be due only to some sub- 
 sequent variation, are present from the first. 
 
 Origin and Development of the Bladder- Worm of the Pig, 
 (Cysticercus cellulosie, Auctt.). 
 
 To Kiichenmeister is due the permanent merit of having first dis- 
 covered the relations between the hook-bearing Tcenia solium and 
 the common bladder-worm of the pig the Cysticercus cellulosce of 
 earlier helminthologists and of having thereby given a proper direc- 
 tion to our views regarding the life-history of this parasite. What 
 induced Kiichenmeister to claim the bladder- worm of the pig as the 
 larval state of the tape -worm, was principally the structure of the head 
 and hooks, which so perfectly correspond in the two forms, that the 
 most careful investigation can establish no differences between them. 1 
 The differences in pigmentation which are occasionally observed, and 
 which consist mainly in the head of the bladder -worm being of a 
 lighter shade, or indeed entirely without colour, can form no obstacle 
 to an association of the forms, especially as it is well known that the 
 adult tape-worms exhibit many variations in this respect. 
 
 Kiichenmeister's statements had of course the effect of defining in 
 a more satisfactory manner the question regarding the origin of Tcenia 
 
 1 " Ueber Cestoden im Allgemeinen," pp. 78, 89, 1853. 
 
EXPERIMENTS BY THE METHOD OF FEEDING. 491 
 
 solium, and confirmatory opinions were immediately expressed. 1 But 
 his view did not obtain general acceptation until the connection of 
 the two parasites was firmly established on experimental grounds, and 
 that principally by the proof that the eggs of Taenia solium develop in 
 the pig into the familiar bladder-worm of the muscles, and also that this 
 is the larval form of the Tsenia. 
 
 The first attempt of this kind was made by van Beneden, who 
 fed a pig with a tape-worm, and four and a half months afterwards 
 found it to contain bladder- worms. 2 No proof was given, however, 
 that these bladder-worms originated from the eggs of the worm 
 administered, so that the result of the experiment cannot be regarded 
 as completely convincing. But any doubt which might have existed 
 on this point has been entirely removed by the experiments of 
 Haubner and Kuchenmeister. 
 
 Haubner administered 3 at different times single proglottides and 
 larger pieces of tape-worm to five young pigs, which came of a brood 
 free from bladder-worms, and succeeded thereby in infecting three of 
 them with bladder-worms. The two other pigs remained uninfected 
 in spite of the feeding ; but this negative result cannot in any way 
 affect the cogency of the argument, since in the three other cases 
 the degree of development of the bladder-worms was proportionate 
 to the period that had elapsed since the feeding. 
 
 The first pig was killed thirty-two days after the first feeding and 
 thirteen days after the last. It harboured in different parts of the 
 body isolated bladder-worms, altogether about forty or fifty, the 
 majority being found in the neck. The largest were about the size of 
 a hemp-seed, and showed the first rudiment of the head as a minute 
 opaque spot. 
 
 The second pig was dissected forty-six days after the first and 
 twenty-seven days after the last feeding, and was found to contain 
 several thousand bladder -worms, which were distributed over the 
 whole body, some of them being as large as a pea, while the smallest 
 were about the size of a hemp-seed. Microscopic investigation 
 revealed in the more advanced bladder-worms a distinctly formed 
 head, with the rudiments of hooks and suckers at various stages of 
 development. The head -process shone through the walls of the 
 
 1 I was the first to express myself frankly, and indeed on the ground of my own 
 investigations, in favour of Kuchenmeister's statements. I frequently had heads of 
 different bladder- worms submitted to me by scientific friends for examination and identi- 
 fication, but could never succeed in distinguishing those of Cysticercus celluloses and of 
 Tcenia solium from each other, and always regarded them both as heads of the same 
 species, like those of Cysticercus tenuicollis and T. marginata, &c. 
 
 2 Ann. sci. nat., t. i., p. 104, 1854. 
 
 8 Gurlt's Magazinfur Thierarzneikunde, p. 105, 1855. 
 
492 HISTORY OF CYSTICERCUS CELLULOSE. 
 
 bladder in the form of an opaque spot. In the third pig, killed sixty 
 days after the first and forty-one days after the last feeding, such a 
 large number of bladder- worms were found, that a single half ounce 
 of flesh contained 150. The largest were almost mature as regards 
 size, form, and the development of the head, while the smallest were 
 like the largest ones in the second pig. 
 
 An experiment made by me at almost the same time afforded 
 exactly the same result. There were also five pigs, most of which I 
 fed several times with tape-worm (expelled by various anthelminthics, 
 and especially by cousso and pomegranate bark). I examined the pigs 
 at varying intervals after the commencement of the experiment. l 
 
 In one case a dissection was made of the animal forty and thirty- 
 two days after the first and last feedings respectively. The bladder- 
 worms were extremely numerous, from 1 mm. to 5 mm. in length, and 
 the largest were already oblong in form. They were found chiefly in 
 the muscles of the belly, breast, and neck, also in the diaphragm, and a 
 few in the brain and liver. The parenchyma of the lungs contained a 
 number of small white cysts, probably representing a brood which 
 had found ingress, but had not become further developed. The head- 
 process was distinctly visible in all of them, but was generally small, 
 and, even in the largest bladder-worms, still without any trace of 
 suckers and hooks. And if it were d priori probable that the bladder- 
 worms originated from the administered tape-worm, this was estab- 
 lished beyond all doubt by the fact that a muscle extracted from the 
 pig ten days after feeding contained as yet no bladder-worms. 
 
 The sterno-hyoid muscle of a second pig, fed in the same way, 
 exhibited, after forty-two days, bladder-worms of the same stage of 
 development as the above case, but surprisingly smaller, although the 
 animal was fed with equal portions and belonged to the same litter. 
 The dissection was not made until 124 days after the feeding, the 
 animal having twenty days previously eaten a second tape- worm. The 
 bladder- worms had meanwhile attained a length of 12 mm., and a 
 breadth of 5'5 mm. They were fully developed, having a head-process 
 3 mm. long. In number they amounted to some hundreds, while in 
 the first pig there would be, perhaps, as many thousands. 
 
 The majority of them were found in the muscles of the breast and 
 neck, and also in the brain ; but in the latter situation the parasites, 
 although fully developed, hardly measured more than 5 to 6 mm. 
 The last feeding seemed to have been almost without results. Only 
 in the brain some small bladder-worms were found of 1/5 to 2 mm. in 
 length, and with a newly formed rudimentary head. 
 
 1 Two of these experiments have already been mentioned in my treatise, " Blasen- 
 band warmer," p. 48, 1856. 
 
DETAILS OF FEEDING EXPERIMENTS. 493 
 
 The examination of the third pig, which had been fed three times, 
 took place 107 days after the first, seventy-one days after the second, 
 and forty days after the last feeding. Even while cutting through 
 the skin, I was convinced that the experiment had succeeded. The 
 hladder- worms were so abundant, that in many places the flesh seemed 
 changed into a honey-combed mass, somewhat like the spawn of frogs 
 or fish, and the number of the parasites amotinted to at least 12,000. 
 The heart, lungs, and brain contained them, although in smaller 
 numbers than the locomotor organs. Instead of bladder-worms, the 
 liver exhibited only some tubercle-like nodules : the eyes were also 
 free from bladder-worms that is to say, the ball of the eye for 
 many were contained in the muscles of the orbit, and there were also 
 some under the conjunctiva. The largest bladders had a longitudinal 
 diameter of about 8 mm., while the smallest, which occurred in the 
 brain, measured only 2'5 mm. The other bladder-worms in the brain 
 were also smaller than those in the rest of the body, for the largest did 
 not exceed 4' 5 mm. Most of them lay free on the surface of the hemi- 
 spheres, below the pia mater, or between the convolutions. Others 
 were sometimes free in the ventricles, between the convolutions, and 
 sometimes embedded in the substance of the brain, and then enclosed 
 in a sort of capsule. Some specimens were also found between the 
 lamellse of the dura mater ; these formed projections which had left 
 deep impressions on the internal surface of the roof of the skull. As 
 regards the stage of development of the head, the parasites might be 
 divided into three groups, which probably corresponded with the three 
 feedings. The largest were fully developed, others exhibited various 
 earlier stages of the hooks and suckers, while the youngest had only 
 the first rudiments of a head. The latter were found exclusively in 
 the cavity of the skull, from which, however, the representatives of 
 the second stage seemed to be absent. 
 
 The fourth pig, which was killed eighty-two and twenty-nine days 
 after the first and second feedings respectively, appeared at first quite 
 healthy. Only after a long search was a single bladder-worm found 
 deeply buried in the muscles of the neck. It was the size of a large 
 pea, and was fully developed. 
 
 In the case of the fifth pig, as in the first and second, excisions of 
 muscles were made from time to time, in order to study the gradual 
 development of the bladder- worms, which were again present in con- 
 siderable numbers. Eight days after the feeding, no parasites could 
 be found, but many were visible on the second and third excisions, 
 which were postponed till the thirtieth and ninety-fifth days. The 
 pig, which had meanwhile been subjected to other experiments, lived 
 for some time, and on dissection (six months after the feeding) it ex- 
 
49 J: HISTORY OF CYSTICERCTJS CELLULOSE. 
 
 hibited perhaps 2000 to 3000 full-grown bladder-worms, which, with 
 few exceptions, were confined to the peripheral muscles of the body. 
 
 FIG. 277. Measly pork (nat. size). 
 
 The experiments which we have mentioned are not, however, the 
 only ones of the kind. Similar investigations have often been made 
 since, especially by Mosler 1 and Gerlach, 2 some of whose observations 
 we shall shortly notice more particularly. I have also been able to 
 give the results of some new feeding experiments. 3 The results agree 
 in all points with the foregoing statements, so that there can no 
 longer be the slightest doubt regarding the relations existing between 
 the bladder-worm and Tcenia solium. This might certainly have been 
 affirmed sooner, but any new idea makes but slow progress. Yet even 
 after these experiments had been made, not only by van Beneden but 
 by Haubner and myself, an attempt was made to weaken their 
 cogency by the objection that the investigators had possibly procured 
 the animals for their experiments from districts in which the tape- 
 worm disease was an epidemic. 4 This is assuming, very unwarrant- 
 ably, that our conclusions are based merely upon the presence of the 
 worms after the feeding. On the contrary, whoever examines these 
 conclusions impartially will be convinced that their cogency is due to 
 a much greater extent to the constant correspondence of the degree of 
 development of the bladder- worms with the duration of the experiment. 
 The mere presence of the parasites might possibly be explained in 
 some other way, although the number of pigs infected with bladder- 
 worm could hardly amount anywhere to eighty or even more per cent., 
 
 1 " Helminthologische Studien und Beobachtungen," p. 43, 1869. 
 
 2 Zweitcr Jahresber. d. k. Thierarzneisch. Hannover, p. 66, 1870. 
 
 3 First German edition of this work, Bd. i., p. 745. 
 
 * See Davaine, loc. cit. t first edition, p. xxx. In his second edition, indeed (1877), 
 Davaine abandons his hesitation. Even he now acknowledges the cogency of the feeding 
 experiments. But it is very strange that the most convincing one of all namely, my 
 own which is the only one that proves the development of the bladder-worms within the 
 same host (as before), is passed over in silence (loc. cit., p. 913). 
 
THE TAPE-WORM DEVELOPED FROM THE BLADDER-WORM. 495 
 
 but the gradual progress of the development in proportion to the 
 duration of the experiment admits of only one interpretation. 
 
 Nor is even this consideration necessary to refute this objection. 
 The validity of the experiments is obvious. Shortly after the com- 
 mencement of one of my experiments, I was directly convinced of 
 the absence of bladder-worms in two of the animals. And some 
 weeks later the muscles were inhabited by thousands of young 
 bladder-worms. In view of these facts, could there possibly be any 
 doubt ? 
 
 The differences in the number of resulting bladder-worms do not, 
 of course, affect our conclusions ; nor do a few negative results. 
 They only prove that the development of the tape-worms, as of other 
 Helminths (p. 85), is determined by certain conditions, which are 
 differently expressed in different animals. Even where the bladder- 
 worms were most numerous, only a few of the introduced eggs had 
 reached maturity. The pig with 12,000 bladder- worms had eaten 
 three tape-worms. If we allow each of these sixty ripe joints, and 
 take the space containing eggs at 6 cub. mm., then the total number 
 of eggs (which have a diameter of 0*06 mm.) cannot have been less 
 than a million, of which only about 12,000, .or about 1 in 100, 
 reached maturity. A single tape-worm joint might theoretically 
 produce about the half of those 12,000 bladder-worms ! 
 
 It must at present remain undecided whether Gerlach's report be 
 correct or not, that only young pigs are capable of infection. He 
 asserts that at an age of six to nine months feeding experiments 
 always fail. 1 
 
 The experimental proof of the specific identity of Tcenia solium 
 and Cysticercus celluloses is furnished not only by the rearing of bladder- 
 worms, but also by the metamorphosis of the latter into the tape- 
 worm. 2 
 
 Kiichenmeister made an experiment in which, through the prison 
 medical officer, seventy-five pieces of bladder-worm from the pig were 
 given to a condemned criminal during the last three days of his life. 
 They were concealed partly in cooled soup and partly in sausage. 
 Some days before, for want of Cysticercus celluloses, a C. tenuicollis ami 
 six pieces of Cysticercus pisiformis had been given to the criminal. 
 When the corpse was examined forty-eight hours after death, ten 
 young Tcenice, mostly 3'4 mm. long (with one of 6'8 mm.), were 
 found in the small intestine. By the nature of the posterior part of 
 their body, they showed distinctly that they had just left their cystic 
 state. Unfortunately only four of these young tape-worms were 
 
 1 Loc. cit., p. 67. 
 
 2 Wiener mcd. Wochenschr., No. L, 1885. 
 
496 HISTOKY OF CYSTICERCUS CELLULOSE. 
 
 provided with hooks. Although these forms were in Kiichenmeister's 
 opinion indubitably derived from Cysticercus cellulosce, yet, consider- 
 ing the different species used in feeding, and the slight development 
 of the Tcenice found, and the striking smallness of the number, some 
 doubt as to the cogency of the argument is not unreasonable. 
 
 Thus it seemed very desirable that such experiments should be 
 repeated, and an opportunity soon offered. A young educated man 
 of about thirty years of age, and of healthy constitution, to whom I 
 had explained the development of the tape-worm, offered himself in 
 the interest of science as the subject of experiment. He swallowed 
 in my presence four bladder- worms, which I gave him in luke-warm 
 milk, after cutting off their caudal bladders. Two and a half months 
 afterwards he observed in his stools detached segments of a tape- 
 worm with which he had never before been troubled. The experi- 
 ment had thus succeeded, and four weeks afterwards I examined two 
 worms about 2 metres long whicli had been voided by the patient 
 after a few doses of cousso. Only one of these had a head, which 
 of course exhibited the structure of Twnia solium.' 1 
 
 I made two other experiments, each time with twelve bladder- 
 worms. The one case was that of a man bribed by money, who 
 suffered from Bright's disease ; the other that of a consumptive 
 patient suffering from profuse diarrhoea, who served unconsciously 
 as the subject of experiment. Both were without result. 
 
 According to the memoirs of van Beneden and Davaine, a student 
 in Geneva, Humbert by name, made a similar successful experiment 
 upon himself. Before the eyes of Vogt and Moulini^, he swallowed 
 fourteen bladder- worms from the pig, and voided the first proglottides 
 during the lapse of the third month. After taking a purgative, the 
 patient remained for a long time apparently free from his worm, but 
 some months later he again noticed the expulsion of proglottides. 
 These exhibited, as before, all the characters of Tcenia solium.* 
 
 Similarly Hollenbach, who swallowed a teaspoonful of bladder- 
 worms, expelled five months afterwards a piece of tape-worm five 
 feet long, with many joints, but without the head. 3 It was referred to 
 Tania serrata, but must have been the ordinary human tape-worm, 
 being designated as above only on the authority of v. Siebold, who, as 
 is well known, denied for a while the specific distinctness between the 
 large-jointed Tcenia of man and of the dog (p. 405). 
 
 1 " Blasenbandwurmer," p. 53, 1856. 
 
 2 So Bertolus reports "Dissert sur lea metamorph. des cestoides," (These de Mont- 
 pellier, No. 106, December 1856, cited by van Beneden, "Zool. meU," t. ii.). 
 
 3 Wockcnschrift d. Thierheilkunde u. Vichzucht, Adam and Niklas, Bd. ii, pp. 301 
 and 353. 
 
THE HOSTS OF CYSTICERCUS CELLULOSE. 497 
 
 A scrupulous critic may perhaps find these experiments not 
 altogether satisfactory. All the more important is the result of a 
 further experiment made by Kiichenmeister on a condemned 
 criminal. 1 Several months before execution the criminal ate twenty 
 bladder-worms of the pig introduced in a sandwich of sausage. They 
 were administered on the 24th November 1859 and on the 18th 
 January 1860, and the execution took place on the 31st March 1860. 
 The result was the discovery of nineteen tape-worms in the intestine. 
 Eleven of these were short (at most five feet) and thin, but already 
 provided with ripe joints, some of which were still adherent, whilst 
 others were creeping about freely in the lowermost part of the in- 
 testine. The other eight worms were nearly mature. 
 
 Heller has lately reported another such experiment. 2 Eighteen 
 days before death, a consumptive patient ate twenty-five pieces 
 of fresh bladder- worm. On post mortem examination, twelve tape- 
 worm heads were found in the intestine, which showed all the char- 
 acters of Tcenia, solium, but were all very small, and had no joints 
 visible to the naked eye. 
 
 Before such facts the last doubts must vanish. We may safely 
 regard it as fully established that the hook-bearing Tcenici solium 
 springs from the Cysticercus celhdosce. Only those can continue to 
 doubt who do not wish to see the truth. 
 
 The chief host of the Cysticercus cdlulosce is the pig. But 
 it is not the only animal besides man which harbours this form. 
 According to Diesing, this muscle-bladder-worm has also been found 
 in apes, dogs, bears, rats, and deer. Though it occurs but rarely in 
 these animals, we cannot leave the fact out of account, especially in 
 considering the mode in which infection may take place, for the speci- 
 fic identity of these forms with Cysticercus cellulosce has been in some 
 of these instances distinctly established. Apart from those found in 
 the apes, which even Treutler 3 identified, those occurring in the 
 roe have been carefully investigated and identified by Krabbe, 4 
 and by myself. The hooks, which were arranged in fourteen or 
 fifteen pairs, were somewhat thinner and smaller than in the 
 common bladder-worm of the pig, but were otherwise in entire agree- 
 ment, so that there was no reason to doubt their identity. Even the 
 bladder- worm with twenty-six hooks found by Cobbold 5 in mutton 
 
 1 Deutsche Klinilc, No. 20, 1860. 
 
 2 Ziemssen's " Handb. d. sp. Path. u. Ther.," Bd. vii., p. 597 ; English translation, 
 " Cyclop. Pract. Med.," vol. vii., p. 712 : London, 1877. 
 
 3 " Observat. path.-anat," p. 26, Lipsiae, 1792. I have myself identified a bladder- 
 worm from Inuus ecaudatus as Cysticercus cellulosce. 
 
 4 Vidensk. Meddel. Naturhist. Foren., Tab. v., 1862. 
 6 " Entozoa,'' p. 30 : London, 1869. 
 
 21 
 
498 DEVELOPMENT AND GROWTH OF T^ENIA SOLIUM. 
 
 could (from his description) be scarcely distinguished from the ordinary 
 bladder-worm of the pig, although my respected friend is inclined to 
 regard this as an example of a yet unknown species the hypothetical 
 Tcenia tenella, Cobbold. 1 Further, an attempt I made to infect the 
 sheep with T. solium had only a negative result. Maddox 2 also de- 
 scribes a hooked Cysticercus from the muscles of the sheep, but regards 
 it not only as a new species, but as a sexually mature animal (Cysti- 
 cercus oviparus). We must, of course, remember that our knowledge 
 of bladder-worms from the muscles is not yet by any means complete, 
 as is evidenced by the above-mentioned (p. 405, note) Tcenia Krabbei, 
 which Moniez reared in the intestine of the dog from the bladder- 
 worms of the reindeer. Under such circumstances, we must leave it 
 undecided whether the bladder-worm from the muscles of the alpaca 
 (which seems to be very frequent in Peru, since the four animals in- 
 vestigated by Sappey were infested to an extraordinary extent 3 ) should 
 be identified with the Cysticercus celluloses, especially since we do not 
 yet know whether or not it is provided with hooks. 
 
 It is quite otherwise with the bladder-worms of the dog, which, 
 according to Leisering's observations,* are distinctly identical with 
 the bladder-worm of the pig, although my attempt to rear them in the 
 dog from the eggs of Tcenia solium was as unsuccessful as my previous 
 attempt in regard to the sheep. In Leisering's case the bladder- 
 worms were found not only in the muscles but also in the lungs and 
 liver. 5 They were distinguished by their unusual size, but in the 
 viscera they were mostly dead and shrivelled up. J. Vogel gave a 
 similar account a long time before of a blind and apathetic dog whose 
 brain was completely penetrated by Cysticerci.* In the cat also I 
 once found a single large Cysticercus celluloses under the right shoulder- 
 blade. 
 
 Development and Groivth of Trenia solium. 
 
 In the above discussion of experimental investigations, we have 
 already had the opportunity of following the developmental history of 
 this tape-worm with some completeness. We know not only the dif- 
 ferent developmental stages which are passed through, but also how 
 these follow one another. The following summary, based largely on 
 my own observations, will show the extent of our knowledge. 
 
 1 Not to be confused with T. tenella, Pall., which belongs to the modern genus Both- 
 rioccphalus. 
 
 Monthly Micr. Journ., vol. ix., p. 245. 
 Comptes rendus Soc. bid., t. ii., p. 178, 1860. 
 Bericht uber das Veterinarwesen Sachsens, p. 18, 1864. 
 " Pathologischische Anatomic," p. 434. 
 Similarly Gerlach, loc. cit,, p, 69. 
 
EARLY STAGES OF CYSTICERCUS CELLULOSE. 499 
 
 1. The Bladder-worm (Cysticercus celluloses). 
 
 As to the fate of the embryos, and the ways by which they pass 
 from the intestine to the muscles or organs they inhabit, we have un- 
 fortunately but few definite results, but are left to inductive conclu- 
 sions, which are rendered somewhat doubtful by the limited range and 
 uncertainty of our experiments (p. 339). 
 
 The youngest worms we know were seen eight days after the 
 feeding. I have myself sought in vain for these first larval stages. 
 Over and over again I extracted portions of muscle from the subjects 
 of my experiments eight or ten days after the introduction of the eggs, 
 and once sacrificed a whole pig for this purpose fourteen days after 
 the first feeding and twelve after the second, but without result. This 
 blank has, however, been filled up by Hosier's researches. x He de- 
 scribes the young bladder-worms as oval vesicles O033 mm. long, and 
 O024 mm. broad, only slightly larger, therefore, than the former 
 embryos, but further differentiated in that they enclosed granular 
 contents. The six hooks seemed already lost, if one may so infer 
 from his silence regarding them. There was no proper capsule ; the 
 worms lay quite free between the muscular fibres. It was only in the 
 heart that Hosier found these parasites after he had looked through 
 all the muscles of the body in vain. The heart was examined with 
 special care, since the animal had eaten some trichinous flesh in 
 addition to the 180 proglottides, and the Trichinae were looked for 
 specially in the heart. 
 
 What Hosier has said here is by no means the only existing 
 observation on the first young stages of the bladder-worm of the 
 pig. A decade before, an English investigator, Eainey, also found 
 them. 2 He describes them, however, not as free vesicles, but as 
 spindle-shaped tubes, lying inside the muscle-bundle, bearing a thick 
 coating of bristles, and enclosing countless small kidney-shaped bodies. 
 According to him the latter are the beginnings of the tubes; they 
 are said to collect inside the muscular bundle, and then subsequently 
 to become surrounded with an envelope. After the tube has remained 
 for a while in its place of formation, it is liberated by the bursting of 
 the muscular bundle. Shortly afterwards it casts its skin ; the coating 
 of bristles is thrown off, and the contents become, by coalescence of 
 the corpuscles, a tolerably homogeneous granular mass. At the same 
 time the parasite loses its former slender form. It becomes a roundish 
 vesicle, which develops about it a connective-tissue cyst, under shelter 
 
 1 Loc. cit.,p. 52. 
 
 "On the Structure and Development of the Cysticercus cellulosae," Phil. Trans., 
 vol. cxvii, p. 114, 1857. 
 
500 DEVELOPMENT AXD GROWTH OF T^NIA SOLIUM. 
 
 of which it finally develops by increase of size and formation of the 
 head into the familiar bladder-worm. 
 
 The observations on which these statements are based relate only 
 partially to the bladder-worm of the pig. The later stages have been 
 correctly determined, but the first phases do not belong at all to the 
 development of the bladder-worm. They are connected with an 
 entirely different parasitic form, namely, with those organisms which 
 we designate as Miescher's tubes, and rank along with the Psorosperm- 
 saccules. 1 In the first edition of this work 2 I proved their identity 
 with the forms discovered by Miescher and Hessling. Subsequent 
 investigators have confirmed this, so that Rainey's reports do not 
 require further refutation. The mistake will, however, be readily 
 excused by all who know the difficulty of the problem. 
 
 Gerlach was no more fortunate than I was in his search for the 
 youngest stages of the bladder-worm. In a young pig which died of 
 intestinal inflammation nine days after feeding, no trace of the infec- 
 tion was to. be seen. It was different, however, in the case of a young 
 pig which died, without apparent external cause, twenty-one days 
 after feeding. Here there were in the flesh numerous delicate bladder- 
 worm vesicles, transparent, and therefore difficult to detect. They 
 had no enveloping membrane, were about the size of a pin's head, 
 and exhibited a minute transparent point, the first rudiment of the 
 head. 3 
 
 Even before Gerlach, I found 4 in the muscles of a young pig (which 
 had been fed twenty-one days before with about eighty proglottides) 
 young bladder-worms in the form of thin-walled, free vesicles of at 
 most 0'8 mm. in size. They had a spherical form, but were occasionally 
 somewhat narrowed towards the head-rudiment, and provided with a 
 thick border, from which the former projected like a wart. There was 
 no proper cavity to be seen inside, although the cuticle was already 
 somewhat invaginated at the point of attachment. Vessels could not 
 be detected with certainty. 
 
 In addition to these developmental forms, I observed others 
 thirty -two days after the last feeding. They occurred in a young pig 
 which had devoured an immense number of ripe proglottides forty 
 days before dissection. 
 
 The smallest bladder- worms found were vesicles 1 mm. long by 
 07 broad. They lay for the most part in the muscles, but there were 
 some also in the liver and brain. A proper capsule was present only 
 in those found in the liver. Those in the muscles indeed were also 
 
 1 Seep. 199. 3 First German edition of this work, p. 238. 
 
 8 Loc. cit., p. 66. 4 Loc. cit., p. 745. 
 
FORMATION OF THE YOUNG BLADDERS. 501 
 
 surrounded by connective tissue ; for, strictly speaking, the muscular 
 bladder-worms inhabit the inter-muscular connective tissue, but this 
 connective substance is scarcely more strongly developed than usual, 
 and is so far from forming a true cyst, that the bladder-worms fall 
 out immediately when the bundles are separated. The only pecu- 
 liarity of the surrounding connective tissue is the presence of a finely 
 granular substance, which lies next the bladder, and, on closer exami- 
 nation, is seen to be composed of membraneless cells, which enclose a 
 clear nucleus (0*007 mm.), and are so indistinctly marked off from one 
 another that the irregular processes of the borders seem to flow into 
 one another. 
 
 But the bladders were not all of this small size. The great majority 
 were considerably larger between 3 and 4 mm. some had even 
 grown to 6 mm. These differences seem so striking, that I can well 
 believe that the smallest bladder-worms had been retarded in their 
 development, and represented a stage which one would look for about 
 the twenty-fourth day. 
 
 With the increase in size, the surrounding connective-tissue mass 
 has also gradually attained a more marked development, so that, espe- 
 cially in the larger bladder- worms, one can justly speak of a special, 
 though still delicate, capsule. The form of the bladder has also 
 changed, inasmuch as the long diameter with which the course of the 
 fibres corresponds is now at right angles to the axis of the head, and 
 is in some so much increased, that it bears to the transverse axis the 
 ratio of 6 to 2 '5. It is probably, however, only the pressure of the 
 muscles that alters the original spherical form in this way. 1 Similarly 
 we must refer the constantly lateral position of 
 the head-rudiment to the fact that the lateral 
 surfaces of the bladder stand in closer connection 
 with the blood-vessels surrounding the muscular 
 fibres than do the terminal parts. The former 
 have therefore more advantageous conditions 
 of nutrition. 
 
 The Organization of these bladder-worms is , Fl , G - W*>Cy*ticcrcu 
 
 , , . . .. celiulosce with the forma- 
 
 already quite complete, general size and head- tion of the head just 
 structure excepted. Even the smallest are be g innin g- (xio.) 
 vesicles enclosing a clear, non-granular fluid, and exhibiting in their 
 walls a distinct and abundant vascular system, with ciliary lappets 
 
 1 I may mention that I once found two muscle bladder-worms in the same cyst, in 
 which the bladder-body was elongated only at the free outer ends, while the other segments 
 exhibited a simple semi-crescentic structure. Even the older helminthologists have noted 
 the occurrence of two bladder-worms in the same capsule. See the collection of these 
 cases by Stich, Ann. des Charitt-Krankenhauses, p. 169: Berlin, 1854. 
 
502 DEVELOPMENT AND GROWTH OF T^NIA SOLIUM. 
 
 in the fine twigs. The thickness of the wall is still but slight (0'07 
 mm.) : it exhibits below the cuticle two layers, of which the outer has 
 a finely granular tougli character, and is resolved into countless small 
 cells (O007 to 0*01 mm.), while the inner consists of larger drop-like 
 vesicles, which probably have something to do with the secretion 
 of the lymph. The vessels run outside of both these sheaths. 
 They consist of wide and narrow tubes, which partially anastomose 
 with one another in a network, and are so arranged that the finer 
 processes mostly lie towards the exterior. Besides the vessels one 
 finds in the cellular layer numerous strongly refracting molecular 
 granules, and delicate muscular fibres running in various directions. 
 
 The head-rudiment was preceptible even in the smallest bladder- 
 worms. But it was at first of comparatively small size, and so delicate 
 that the least pressure sufficed to destroy it. The point of attachment 
 could also be distinguished at that early stage, since it was marked by 
 small calcareous corpuscles round about the former papilla, and also 
 by the radiate grouping of the muscular fibres running from it. Very 
 soon the head-rudiment appears at the middle point of the bladder. 
 Accompanying the radial fibres which run from it, there are others 
 which embrace the place of insertion, and not unfrequently mark the 
 region round about with wavy wrinkles. Similarly the adjacent 
 vessels grow in course of time into considerable stems, which run 
 towards the head into which they pass, or, what comes to the same 
 thing, run from the head into the bladder. 
 
 In the smallest bladder-worms the head -rudiment was, as we 
 have said, of but small size. It appeared as a plump rounded ap- 
 pendage of 0*12 mm., which was seated on the wall of the bladder, 
 and hung into the cavity in the direction of the smallest radius, cor- 
 responding, that is, to the equatorial axis of the 
 oval vesicle. It is penetrated internally by a wide 
 blind canal, which runs down the axis and opens 
 on the external surface of the bladder, so that the 
 cuticle of the latter is continued through the 
 opening into the head-papilla. The wall proper, 
 like the vascular layer of the bladder- wall, consists 
 of s">all nucleated cells, 
 with rudiment of the With increase of size the head-papilla soon 
 
 receptacle. (x25.) j oges ^ swo u en f orm J t g rows an d becomes 
 
 by elongation a more club shaped structure, whose internal cavity is 
 enlarged like a bottle at the lower blind end (Fig. 279) : when the 
 rudiment is about 0*2 mm. long (in bladder-worms whose longest 
 diameter measures about 1*5 mm.), then histological differentiation 
 begins. Not only can one distinguish on the outer surface a thin 
 
FORMATION AND DEVELOPMENT OF THE RUDIMENTARY HEAD. 503 
 
 layer of fibres, which pass from the head into the musculature of 
 the bladder, and which must have been previously present in a 
 less developed state, but also cells of another nature lying next the 
 cuticle, which have a different appearance, inasmuch as they assume 
 a spindle form, and impart to the deeper layer a very striking 
 radiate character. 
 
 We need hardly expressly mention that the outer muscular layer 
 of the head-rudiment represents that structure which we formerly 
 designated the "receptacle," and which we saw to be of general 
 occurrence in the larger cystic tape-worms (p. 346). 
 
 This receptacle lies at first close upon the outer surface of the 
 head-papilla. For a while the two structures grow with perfect 
 uniformity, but soon one sees, in bladder-worms about 2*5 mm. long, 
 that the head-papilla obviously, in consequence of its greater longi- 
 tudinal growth, curves round in a bow inside the receptacle, and 
 assumes a bent position (Fig. 280). As long as the curve is not very 
 marked, the club-shaped end of the head lies still, almost perpen- 
 dicularly under the point of attachment, but afterwards it bends more 
 and more to one side, until the angle finally (Fig. 281) comes to lie 
 at the deepest point of the receptacle. The latter thereby loses its 
 former regular shape ; the lateral surface which lies next the end of 
 the head is protruded like a hernia ; thence it bridges over the angle 
 between the two portions of the bent head, and passes towards the 
 point of insertion. 
 
 FIG. 280. The beginning 
 of the bending of the head 
 of Cysticercus celluloses 
 inside its receptacle. ( x 25.) 
 
 FIG. 281. The head and re- 
 ceptacle of a bladder-worm from 
 a muscle about 6 mm. in size. 
 (x25.) 
 
 In this state the head-rudiment persists until the long diameter 
 of the bladder-worm has increased to about 6 mm., 1 when it 
 
 1 Since these early stages of Cysticercus celluloses have not been before observed in 
 man, I may note that similar forms were once (1860) sent to me for examination and 
 identification by my colleague Professor Wagner of Leipsic. They originated from the li ver 
 in a case of tuberculosis, were about one line in size, and occurred in considerable numbers, 
 about one for every square inch. 
 
504 DEVELOPMENT AND GROWTH OF T^DNIA SOLIUM. 
 
 usually measures about 1 mm. But this length is almost equally 
 divided between the two joints, one of which effects the connection 
 with the wall of the bladder to which it is attached perpendicularly, 
 while the other enclosing the enlarged blind end of the head-cavity 
 is bent to the side, almost at a right angle. The receptacle sur- 
 rounding the head has departed from its previous form in being 
 laterally protruded before the bend of the head. Breadth and height 
 measure somewhat uniformly 0*5 mm. The space running up the 
 axis of the papilla is but slightly enlarged, except at its blind end. It 
 has for the most part the appearance of a narrow canal, and in the 
 basal portion is not straight but of zigzag form, and therefore longer 
 than the linear distance between its ends. This form is obviously the 
 optical expression of a folding of the wall of the papilla, and is some- 
 times so inconstant that the application of pressure and simultaneous 
 elongation and broadening out of the canal cause it to disappear. 
 The opening of the canal on the bladder appears usually as a transverse 
 slit, whose borders protrude in the form of two narrow lips. The 
 calcareous bodies which surround this slit in a circle have increased 
 in number, and have also spread themselves over the root of the head- 
 papilla. Otherwise, the structure and histology are much as before. 
 Internally, one recognises here and there the subsequent longitudinal 
 vessels, but always only in fragmentary fashion, since they are easily 
 destroyed by pressure. 
 
 The early bending of the head-papilla here described is, as far as I 
 know, an exclusive characteristic of Cysticerciw cellulosce. In the other 
 bladder-worms known to me the head retains its originally straight 
 position, almost unchanged, until the formation of the suckers and 
 circle of hooks. The flexure, if it occur at all, does not begin till 
 later, when the neck increases greatly in length after the completion 
 of the head. In the bladder-worm of the pig this elongation occurs at 
 an earlier period than usual. 1 
 
 In spite of the marked curvature of the head-papilla, no proper 
 head is yet to be found. The process is indeed enlarged terminally 
 like a club, and the internal canal is markedly enlarged, but there 
 are as yet no traces of suckers or hooks, which are the most important 
 characteristics of the tape-worm head. The next stages, however, 
 result in the formation and development of these organs. 
 
 We may pass over the details of the process with a simple refer- 
 ence to our former discussion (p. 351). There we saw how the suckers 
 originated round the enlarged cavity, but the hooks and rostellum 
 
 1 Perhaps the Cysticercus longicoUis also resembles the bladder-worm of the pig. At 
 least one finds specimens of this worm in which the head-papilla is wound into a spiral, 
 which bears suckers even before the hooks are perfectly developed. 
 
CONTINUED DEVELOPMENT OF THE HEAD AND NECK. 505 
 
 were at the end of the blind process. It sometimes happens, too, that 
 the floor of the cavity (Fig. 281) becomes intruded like a boss, and 
 thus comes to present an appearance which Moniez erroneously 
 regarded as the formation of the tape- 
 worm head (p. 354). It is not this boss 
 which forms the head, but the whole 
 lower end of the head-process a portion 
 so conspicuous that it includes almost 
 the whole portion which is bent to the 
 side. 
 
 During the development of the later 
 head the process has been continuously -, 
 
 . . . ml ' FIG. 282. Metamorphosis of the 
 
 increasing in Size. The receptacle, tOO, head-process into the head proper 
 
 has gradually grown to a length and in ^ysticercus cettulosce. ( x 20.) 
 breadth of 1*3 mm. or more. The histological development is now 
 complete. One can recognise not only the characteristic musculature 
 of the suckers and of the rostellum, but may also distinguish the 
 muscular fibres running in various directions. In suitable pre- 
 parations the vascular system is perfectly distinct. It consists of 
 four longitudinal stems, which give off several lateral twigs, and are 
 connected together between the rostellum and suckers by a circular 
 vessel. Similarly the hooks gradually attain complete development. 
 Not unfrequently one sees round about them small isolated points, 
 the remains of the primitive spines (p. 352). 
 
 With this process the development of the bladder- worm essentially 
 ends. The changes which afterwards ensue, after the course of the 
 second month, mostly concern only the upper 
 portion of the head-process, which is attached 
 to the still continuously growing bladder- 
 wall. This neck-like portion at first hardly 
 predominates over the enlarged lower portion, 
 but after the formation of the head proper it 
 begins to grow rapidly, and, by the formation 
 of numerous calcareous corpuscles, 1 to pre- 
 sent continually a more distinct anatomical 
 contrast to it. In other words, the de- 
 velopment of that cylindrical body begins, ,, 
 
 ,.,. . * i 4 j !_*- FlG - 283. Completion of 
 
 which is usually intercalated between the the head formation in Cysti- 
 head and .bladder - wall, and which resembles cercu8 ceUulos(K - ( x 15.) 
 the subsequent tape -worm body to such an extent that one may for 
 a while consider the two as identical. The growth progresses both 
 
 1 Moniez is mistaken in disputing the existence of calcareous corpuscles in this worm, 
 " Essai, &c.," loc. cit., p. 57. 
 
50 G DEVELOPMENT AND GROWTH OF T^NIA SOLIUM. 
 
 in breadth and in length, and that so quickly that the enveloping 
 receptacle rapidly acquires double or triple its former diameter. 
 
 In spite of this increase in size, the head-process still retains its 
 early position inside the receptacle. The flexure, however, gradually 
 passes into a spiral curvature, and the head is more or less raised by 
 the growth of the succeeding portion. With increased age and length, 
 the spiral becomes more perfect, so that one finds specimens where the 
 head-process exhibits one and a half turns and more. In its unrolled 
 state the body of the worm measures about 10 mm. long by almost 
 2 mm. broad. In order to understand how so large a body can find room 
 inside the receptacle, we must remember that the body of the worm is 
 not only spirally coiled, but is also abundantly wrinkled and folded 
 transversely. There are but few bladder-worms where the head- 
 process is equally folded. In longitudinal sections one sees (Fig 286) 
 the boundary on either side raised in long, thin, comb-like processes, 
 interlocking with each other like fingers, and almost filling up the 
 internal cavity. Here and there the folds are also beset with small 
 elevations. Still more striking is the fact that the head-process of 
 the adult bladder-worm seems to stand in no direct connection with 
 the bladder. 
 
 FIG. 284. The FIG. 285. The FIG. 286. Longitudinal sec- 
 common bladder- same, with evagi- tion through the head-process 
 worm of the pig, natedhead. (x 2.) of the same, (x 40.) 
 with invaginated 
 head, (x i) 
 
 Instead of being attached to it, as before, at the margin of the invagi- 
 nation, the latter is now separated off, so that its basal end protrudes 
 freely into the head-cavity, like the proboscis of a gasteropod. The 
 connection between the head-cavity and the invagination opening is 
 thus effected by a sort of outer cavity, including mainly the basal 
 portion of the head-process. It does not remain exclusively confined 
 
PECULIAR ARRANGEMENT OF THE HEAD-PAPILLA. 507 
 
 to this, but surrounding the greater part of the rolled-up process, as a 
 narrow space separates the latter in many places, as far as the last 
 segment, from the surrounding receptacle. 
 
 I must confess that I did not at first recognise this peculiar 
 character of the head-process, which I know only in the bladder-worm 
 of the pig. I first understood it when I became convinced that the 
 formation of this outer cavity, which isolates the head, results from an 
 annular fold which surrounds the base of the latter, and is distin- 
 guished essentially from the other folds of the internal space only in 
 this, that it develops to a greater depth, and grows round the whole 
 mass of the head-process like a bell. 1 Traces of this fold are present 
 in other bladder-worms. Thus, for example, in the Cysticercus from 
 the crow, described and figured above (p 343), the basal fold has only 
 to be deepened and expanded like a bell in order to isolate the head- 
 process, just as in the adult bladder-worm of the pig. 
 
 It is obvious that the " outer cavity," in spite of its peculiar 
 character, represents an integral part of the head-cavity, for its wall 
 exhibits the same folds as we have seen to exist over the whole length 
 of the latter. The outer wall is indeed destitute of these folds, but 
 that is probably because of its slight thickness, and of the tension to 
 which it and the receptacle in general are subject. 
 
 This unusual condition of the head-process deserves special notice, 
 if only because the early observers were largely mistaken as to the 
 position and attitude of the latter within the receptacle. This is par- 
 ticularly the case with Eobin's figures, reproduced by the elder van 
 Beneden 2 and by Davaine, 3 which are at least false, in so far as 
 they show the head-process rising from the base of the receptacle 
 (" vesicule interieure," Dav. ; " membrane enveloppante," van Ben.). 
 If one press the tsenioid body of the bladder -worm out from the re- 
 ceptacle one may indeed see such appearances as Davaine figures 
 (after Robin) ; but a closer examination shows how false are con- 
 clusions drawn from such cases. This fact alone is conclusive, that 
 the body protruding from the rupture shows the head, not in its 
 evaginated state, as Davaine represents it, but invaginated, as it 
 originally appeared, with cuticle and hooks internally. 4 Much more 
 correct and satisfactory are Steinbuch's representations, which, though 
 
 1 The only one who has described this peculiar structure before is Moniez, but he 
 seems to me to have no correct idea of its true nature (loc. cit., p. 56). 
 
 2 "Zoologie me'dicale," loc. cit. 
 
 3 Loc. cit., p. 39, Figs. 3 to 6. 
 
 4 Kiichenmeister has figured the circlet of hooks in a bladder-worm head pressed out 
 in this way, as the "Apex of the head (Vorderkopf) of Tcenia solium" (" Parasiten," 
 first edition, tab. iii., Fig. 8). 
 
508 DEVELOPMENT AND GROWTH OF MNIA SOLIUM. 
 
 dating from the year 1801, x are really the best researches on the 
 structure of Cysticercus cellulosce until modern times. He recognises 
 not only the connection between the head-process and the bladder, but 
 knows also that the former is hollow up to the circlet of hooks, and is 
 invaginated in itself, so that, when pressed, it can be protruded from 
 the opening of the bladder like a snail's tentacle. Nor does the exist- 
 ence of the above-described outer cavity escape him, although he does 
 not quite correctly grasp its relations to the receptacle, which even 
 Werner has recognised and described as a tunica vaginalis.* 
 
 Although the head-process is in reality an integral part of the 
 bladder, and, until its separation, is in connection with the organs and 
 tissues of the latter, yet one must not directly identify the two por- 
 tions in their anatomy and histology. Both differ in fact widely, much 
 more indeed than do the head and joints of the adult tape-worm, 
 whose genetic relations are very similar. These differences include 
 more than the specific organization of the head-proper, and persist 
 between the bladder and the cylindrical body of the worm. 
 
 What strikes us at once is the different thickness and firmness of 
 the body-wall. This is thin and tender on the bladder, but acquires a 
 considerable thickness, and a much firmer character when it is con- 
 tinued to the attached process. The connective-tissue becomes less 
 abundant, the musculature greatly increases, and the fibres form, as we 
 have seen, regular layers and bands. The calcareous corpuscles 
 embedded between the latter serve to increase the firmness of the 
 structure. Not less marked is the thickness of the cuticle, which is 
 fully four, or even six, times as great as that of the bladder, although 
 it turns its surface, not towards the exterior, but towards the interior 
 of the body of the worm. The subjacent subcuticular layer is also of 
 considerable thickness. It exhibits the same structure as the sub- 
 cuticula of the adult tape-worm indeed the cylindrical body of the 
 bladder-worm is in all essential features like the latter. 
 
 1 " De Taenia hydatigena anomala," Dissert, inaug., Erlangen, 1801. As specially 
 characteristic, I may quote these sentences : " Taenise corpus in se ipsum retractum atque 
 mirifice involutum figuram globosam repraesentat " (p. 17). " Vermis corpus canalis mem- 
 branaceus, cavus, conice elongatus, et rugis seu plicis circularibus compositus est" (ibid.). 
 " Extremitas crassior superficiei internae vesicae caudalis imposita atque adnata aperturam 
 vesicae circuradat" (ibid.). " Taeniae corpus quiescent* in se ipsum inverse est retractum" 
 (p. 36). " Eodem modo vermis ex se ipso procedit, quo tentaculum Helicis in se conver- 
 sum atque retractum invertendo ex se ipso prodit" (p. 21). 
 
 2 Loc. cit., p. 22. " Pars corporis vesicae adhaerenti proxima et in vesicae antrum 
 recedens globuli membranam exteriorem format (usque ad latus, ubi) corporis vermis 
 membrana in se ipsam intus est reflexa." See also the explanation of Fig. 8 "Tunica 
 vaginalia quam adesse opinatus est Werner, non est nisi pars ultima corpusculi taeniae sacci- 
 formis, quae superficiei internae vesiculse caudalis adhaeret ejusque continuationem inaequa- 
 lem reprsesentat." 
 
STRUCTURE OF THE WALL OF THE BLADDER. 509 
 
 The wall of the bladder is quite different, for not only is the 
 cuticular envelope tender and the cells of the subcuticula of a more 
 roundish form, but the musculature in particular is but slightly 
 developed, and is composed of fibres which show by no means such 
 a regular arrangement as in the cephalic appendage. One does 
 indeed find bands of fibres which run from the insertion of the head 
 in a meridional and equatorial direction, but a still greater number, 
 especially deep down, run across one another diagonally. We must 
 further note that the fibres form no closed layer, but leave between 
 them more or less wide meshes, which are filled by the cellular 
 tissue. At the angles of the meshes the fibres are often split, and 
 are united together in a still finer network, which penetrates the 
 whole ground-substance. One even sees muscles in connection with 
 the subcuticula, although it is difficult to get a clear idea of their 
 exact nature. Yet the nature of this connection is an interesting 
 point, since it determines that peculiar tuberculated appearance which 
 even Steinbuch 1 emphasised as a characteristic of the bladder-worm 
 of the pig. Somewhat similar elevations (0'05-0'06 mm. broad by 
 0*025 mm. high) are indeed to be found in the bladder- worm of 
 Tcenia saginata, but they are much less high and much less regular. 
 The other bladder-worms show, instead of the tubercles, somewhat 
 regular transverse wrinkles, which are, as one can easily see in 
 longitudinal sections of Cysticercus pisiformis, occasioned by a fan- 
 like distribution of the meridional fibres attached to the subcuticula. 
 Perhaps, too, the thickness and rigidity of the cuticle, which is much 
 more marked in the bladder-worm just named and in its allies than 
 in those of the human tape-worms, and especially of Tcenia solium, 
 exercises some influence on the nature and appearance of the bladder- 
 wall. We have already mentioned that the vessels of the bladder- 
 wall are, like the muscles, united into a meshwork. We need only 
 add that these meshes arrange themselves at the sides of the head- 
 process in two broad bands, which run from the ends of the bladder 
 towards the middle, and finally pass as longitudinal vessels into the 
 head-process, becoming connected laterally somewhat like a rope- 
 ladder. 
 
 The calcareous corpuscles are distributed singly over the whole 
 wall of the bladder, and are specially abundant in the neighbourhood 
 of the head -process, although never so closely crowded as in the 
 cylindrical body of the worm. 
 
 Before reaching this stage of development, the Cysticercus celluloses 
 must have lived about three or four months. This does not mean, 
 
 1 Loc. cit., p. 11. ''Superficies vesicae externa eminentiis granulosis mimitissimis 
 innumerabilibusque obsita est." 
 
510 DEVELOPMENT AND GROWTH OF T^NIA SOLIUM. 
 
 however, that it might not sooner undergo a metamorphosis into a 
 tape-worm. Since it is not the whole cylindrical body of the worm, 
 as we shall afterwards see, but only the head proper, which becomes 
 the tape-worm, a shorter time is sufficient to render the transforma- 
 tion possible. After the lapse of two months and a half the head is 
 provided with hooks and suckers, and we may even conclude that 
 the bladder-worm of the pig attains maturity before the close of the 
 third mouth. The subsequent changes are limited essentially to an 
 elongation of the cylindrical body. According to all appearances this 
 increase in length is not in any way restricted to a certain age, though 
 in course of time it gradually decreases in rapidity. Even the bladder 
 sometimes increases for a while in size, though usually (and particu- 
 larly in the muscles) it is but little larger than a small bean. 
 
 It is difficult to determine accurately how long the bladder-worm 
 may live and retain its potentiality of development. In the case of 
 bladder-worms from human muscle, Stich * believes, though on the 
 strength of but few and uncertain observations, that from three 
 to six years may elapse. After this period the bladder-worms, 
 easily detected through the skin, lose their elastic character, and 
 one after the other gradually become smaller, and finally dis- 
 appear, on superficial inspection at least. The bladder - worms 
 inhabiting other organs, especially the brain and eyes, may indeed 
 attain a much greater age. There are cases of bladder-worms in 
 the brain which have for twelve to fifteen years excited the most 
 critical symptoms, 2 and by help of the ophthalmoscope a bladder- 
 worm in the vitreous humour has been observed and demonstrated for 
 twenty years." 
 
 It is no longer necessary to give any special proof of the identity 
 of the common bladder-worm of the pig with this bladder-worm 
 occurring in man, 4 the most careful scrutiny reveals no difference 
 between them, and their mode of origin is the same. It does not 
 follow, however, that it is always and only the Cysticcrciis celluloses 
 which infests man. In fact we shall afterwards find that another 
 bladder-worm occurs in man under like conditions, and represents 
 no mere variety, as is the case with other forms, which both 
 
 1 Stich, Annalcn des Charitt-Krankenhauscs, p. 170 : Berlin, 1854. For Lewin's 
 criticism, loc. cit., Bd. ii., p. 645, 1875. 
 
 2 See Lewin, loc. cit., p. 645. 
 
 3 Zttlzer, Klin. Wochenschr., No. 4, 1876. 
 
 4 This special proof has been furnished by Redon, who swallowed four human bladder- 
 worms, and three mouths afterwards voided proglottides of Tania solium. Redon over- 
 estimates, however, the importance of his experiment, when he asserts that the identity 
 of the human bladder-worm with the Cysticercus celluloses was thus for the first time 
 established. (Comptcs rendus, t. clxxxv., p. 676, 1877.) 
 
IIIST011Y OF CYSTICERCUS CELLULOSE. 511 
 
 ancient and modern investigators have wished to establish as distinct 
 species. x 
 
 Soon after the discovery of the human bladder- worm by Werner 2 
 its identity with the Cysticercus cellulusce was recognised by Fischer, 
 and was established by his successors, among whom I would especially 
 mention Stein buch. Werner is not, however, to be regarded as the 
 discoverer of the bladder-worm of the pig, for the occurrence of 
 bladder-worms in the muscles of man had been detected long before. 
 But they were then in nowise regarded as animals either in pig or 
 man, but as glandular tumours (" glandia "), although their animal 
 nature, at least in the case of those from the pig, had been 
 recognised since the end of the seventeenth century by Hartmann 3 
 and Malpighi 4 independently of one another. Hartmann further 
 expresses the probability that the other so-called " glandular tumours " 
 also resulted from intestinal worms. 5 
 
 The fact that the bladder- worms were still considered as tumours 
 and degenerated glands, proves only how difficult it is to displace old- 
 established opinions. The idea was, indeed, an old one, for we find it 
 
 1 Besides Koberl^, to whose opinion we shall return, Brera and Cloquet especially 
 have tried to break up the Cysticercus celluloses of man into several species. (" Compendio 
 di elmintographia humana," 180, p. 24, and " Diet, des sci. med.," t. xxii., p. 165.) 
 
 2 Werner, " Vermium in test, brevis expositionis continuatio tertia," p. 77 : Lipsise, 
 1788. For the first report on bladder- worms in man, see Op. cit., contin. sec., Lipsiae, 1880. 
 
 3 " Miscell. curiosa seu Ephem., Acad. nat. curios.," Dec. ii. Ann. vii. 1688, p. 58. 
 A few years previously (1685) Hartmann also recognised Cysticercus tenuicoUis as a living 
 parasite, and thus for the first time detected the true nature of " hydatids." 
 
 4 "Opera postuma," p. 84, edit. London, 1698. " In suibus verniinosis, qui 
 Lazaroli dicuntur, multiplices stajbulantur vermes, unde horum animalium carnes publico 
 edicto prohibentur. Occurrunt autem copiosi intra fibras musculosas natium, obvia 
 natuque oblonga vesicula folliculus diaphano humore confertus, in quo natat globosum 
 corpus candidum, quod disrupto fojliculo leviter compressum eructat vermem, qui foras 
 exeritur et videtur aemulari cornua exmissilia cochlearum, ejus enim annuli intra se reflexa 
 conduntur et ita globatur animal. Jn apice attollitur capitulum et globati vermem ad 
 extremum folliculi umbilicale quasi yas perducitur." Malpighi had thus even an intimate 
 acquaintance with the head-process, more accurate at least than Hartmann, whose 
 description (loc. cit.) runs as follows : "In corde suis glandia complurima, ultra viginti, 
 in parenchymate utriusque ventriculi intimiori observavi : singulos scrobiculos singulse 
 tunicae albae oppleverant ; tunicis incisjs peculiaris tenuis membranae folliculus eximi 
 poterat, qui praeter limpidum humorem funiculum candicantem fill albi instar convolutum 
 complectabatur, ipsissimum vermiculum." Though Hartmann's description is less intimate 
 than Malpighi's, the right of priority rests with the former. 
 
 " Glandia, aut quocunque nomine his affines veniant pustulae, nidos esse vermiculorum 
 mihi fit verosimile " (loc. cit.). Kiichenineister asserts (" Parasiten," second edition, p. 56), 
 that in this passage, first rescued from forgetfulriess by me, I have " unfortunately " 
 falsely translated "nidos vermiculorum "as " worm nests," while it means nothing more 
 than the place occupied by the worms. I will not discuss which translation is the more 
 correct, but will only note that I have never translated this passage at all (see " Blasen- 
 bandwiirmer," p. 8). Kuchenmeister has often been " unfortunate " when he criticises my 
 assertions as " erroneous." 
 
512 DEVELOPMENT AND GROWTH OF T^EXIA. SOLIUM. 
 
 even in the writings of Hippocrates and in Aristotle, who, in his 
 natural history, ranks the bladder-worms (^aXfat, grandines) among 
 the diseases of swine. 1 The first knowledge of the bladder-worms 
 of the pig is lost in antiquity ; some would, indeed, assert that the 
 Mosaic law against eating the flesh of that animal had not a religious 
 but a sanitary basis. 
 
 Fresh and more accurate investigations were necessary before the 
 animal nature of the bladder- worms of the pig could be generally recog- 
 nised. And these were forthcoming; for shortly before Werner's 
 discovery, mentioned above, Otto Fabricius 2 and Goze 3 has brought 
 forward most convincing proof that the structures in question were 
 true bladder- worms. Since this amounted really only to a confirmation 
 of a previous discovery, both investigations remained unacknowledged, 
 but it was no small merit to have established the nature of the bladder- 
 worms for all future time. 
 
 2. The Adult Tape- Worm. 
 
 The experimental helminthologist can rarely have the opportunity 
 of examining the metamorphoses of the bladder-worm of the pig 
 within man himself. This is not, however, necessary ; for though 
 man is the only host infested with Tcenia solium, he is not the only 
 creature in whose intestine the bladder-worm may attain to further 
 development. Even in other mammals it is possible to follow the 
 first stages, at least, in the metamorphosis. One cannot always reckon 
 with certainty on a positive result, for the experiment often mis- 
 carries the worms are digested, and only the hardly recognisable 
 remains are left. In other cases, however, one finds on examination 
 which must not, of course, be too long postponed 4 the first phases of 
 the metamorphosis of the bladder- worm, which entirely agree with what 
 we have seen (p. 382) in the case of the bladder-worm from the rabbit. 
 
 To refer only to one of my experiments, I fed a rabbit with about 
 thirty pieces of adult bladder- worm from the pig. The dissection 
 
 1 "Histor. Animal.," lib. viii., cap. 81. Here also Kuchenmeister detects something 
 erroneous in my statement. 
 
 3 Nova Acta Soc. Hafn., t. iL, p. 287, or Deutsckes gemeinniitziges Arckiv, Jahrg. ii., 
 Quartal i. : Leipzig, 1788. 
 
 8 " Neueste Entdeckung, dass die Finnen im Schweinefleisch keine Driisenkrankheit, 
 sondern wahre Bandwiirmer sind " : Halle, 1784. The fact that in Goze's great work, 
 which appeared in 1782, there is no mention of the bladder- worm of the pig, has led 
 Kuchenmeister (loc. cit.) to the false conclusion " Goze does not know the Cysticcrcus 
 rellulosce, though Pallas does." I am not aware that the latter has especially considered 
 the bladder-worm of the pig, but Goze has certainly earned a much greater merit by his 
 account of this worm. 
 
 4 Heller's statement that the tape-worms introduced perish after twenty-four hours 
 (loc. cit., p. 597, Eng. transL, p. 718) is somewhat too narrow, as the following case shows. 
 
METAMORPHOSIS OF THE BLADDER-WORM. 513 
 
 took place fifty-one hours afterwards, and was thus postponed some- 
 what longer than usual. I was at first afraid that the experiment 
 was to have only a negative result, but in the terminal portion of the 
 small intestine I found twelve young tape- worms close beside one 
 another. Their relation to, or rather origin from, the bladder-worm 
 introduced, was proved by the nature of their hooks. With one ex- 
 ception (Fig. 287), they were all of the same character small club- 
 shaped worms, scarcely 1*5 mm, long, which exhibited lively move- 
 ments till they became cold. On microscopic examination it was 
 seen that these worms (Fig. 288) represented essentially only the 
 former head of the bladder- worm. The body, 10 to 12 mm. long, 
 which formerly adhered to the head, was lost, all except the short, 
 thin neck. The former, therefore, does not become a part of the 
 future tape-worm in Cysticercus celluloses, any more than in Cysticercus 
 pisiformis or Cysticercus fasciolaris. Only the neck remains as a 
 stalk or stumpy process, connected with the spherical head, which it 
 nearly equals in length but falls far short of in breadth. A small, 
 half-macerated, ragged appendage to the neck is all that remains of 
 the formerly conspicuous body of the worm. 
 
 FIG. 287. Bladder-worm from FIG. 288. Head of Tcenia solium from the 
 
 the pig, after the digestion of the intestine of a rabbit, in different stages of motion, 
 bladder, (x 20.) ( x 25.) 
 
 To the above there was one exception (Fig. 287). This still re- 
 tained a portion of the former body of the worm. The greater part 
 was lost, and the remainder was rapidly going, but it was still large 
 enough to make this one triple the size of the others. 
 
 The result was, as we have said, in entire harmony with the results 
 of our investigations of other cystic tape-worms ; one fact was, however, 
 striking that the development had not progressed further in the two 
 days which had elapsed since the introduction of the bladder-worms. 
 In the tape-worms of the dog the above-described state is found twelve 
 to fifteen hours after feeding. At the end of the second day they 
 show a distinct segmentation on the considerably elongated body. 
 
 2K 
 
514 GROWTH AND DEVELOPMENT OF T^ENIA SOLIUM. 
 
 The difference in this case is probably to be explained by the fact 
 that the animal used does not afford the proper habitat, which, indeed, 
 is found only in man. 
 
 The youngest tape- worms as yet observed in man are those which 
 Kiichenmeister found in the criminal fed by him seventy-two and 
 sixty hours respectively before death. These specimens measured 
 from 3 to 4 mm. in length (with the exception of one only which was 
 twice as large), and showed on the posterior end of the body, where 
 the bladder had been attached, a small notch-like constriction, as is 
 seen in all tape-worms immediately after their separation from the 
 bladder (p. 382). Nothing is said about segmentation, but we can 
 well believe that it was present, at least in the larger specimens. 1 
 
 Had the nature of the end of the body been different, we might 
 have taken the young worms for Tcenice, which, by the loss of their 
 joints, had been reduced to head and neck, and were now commencing 
 the formation of a new chain of joints. The changes undergone by 
 the young tape-worm are exactly like those exhibited by a surviving 
 head. The posterior appendage lengthens, and separates into a series 
 of joints, which become posteriorly more and more marked, as they 
 become separated by the intercalation of new segments ever further from 
 their point of origin. At the same time they are rapidly growing in 
 size and development, so that from an inconspicuous head a very con- 
 siderable chain soon results. 
 
 Although Tcenia solium is decidedly behind T. saginata in its size 
 and in the number of its joints, it is still one of the most conspicuous 
 cystic tape- worms, for it exceeds the other species of this group by at 
 least a metre. This predominance is not determined by the proglot- 
 tides remaining longer united, but, as in T. saginata, by a luxurious 
 vegetative growth and formation of joints, which proceed so quickly, 
 indeed, that the individual development is to a certain extent out- 
 stripped. As in the hookless tape-worm of man, the joints attain 
 their final size and development only at a considerable distance from 
 the head. 
 
 But the form of the tape-worm and the growth of the joints are 
 perhaps best expressed by measurements. I shall first refer to an 
 animal about 224 cm. (that is, about 9 feet long), which was found 
 
 1 Heller reports, in the case mentioned on page 497, that he found " no joints visible 
 to the naked eye " on the " very small " tape-worms, even eighteen days after the trans- 
 mission of Cysticercus cdluloscc. This does not, however, prove the real absence of seg- 
 mentation, for we may compare it with his other statement that the segmentation in the 
 adult Tcenia solium begins 3 cm. behind the head. The first joints are so small that they 
 are hardly ever recognisable by the naked eye. The remark that the worms were all 
 very small, leads one also to conjecture that the conditions of development the experiment 
 was made on a consumptive patient were but slightly favourable. 
 
DIMENSIONS OF T^NIA SOLIUM. 
 
 515 
 
 neither in strong contraction nor in great extension, and was there- 
 fore in so far normal. 
 
 The neck was attached to a head 1 mm. broad, and had at first a 
 diameter of 0'45 mm. It exhibited at the end of the first 25 crn. 
 a breadth of 2*2 mm. The number of joints in this length was of 
 course very great. They amounted to 377, of which 112 belonged to 
 the first 2 cm., since the foremost joints were only 0*01 mm. long. The 
 other joints were thus distributed: the following 6 cm. had 123 joints 
 (of which the last were 07 mm. long by T2 mm. broad) ; the next 9 
 cm. had 82 (with a maximum length of T2 and a maximum breadth of 
 1*4 mm) ; the last 8 cm. had 60 (with a maximum length of 1*5 and 
 a maximum breadth of 2*2 mm.). 
 
 In the second 25 cm. the breadth increased from 2*2 mm. to 4'5 
 mm., and the number of joints sank to 129. On the first third there 
 were 50 joints (of which the last were 2 mm. long by 3'3 mm. 
 broad) ; the middle portion bore 42 (with maximum length of 2*2 
 and maximum breadth of 4'3 mm.) ; while the third portion had 37 
 (the last joint being 2*3 mm. by 4*5 mm.). 
 
 The third length of 25 cm. contained on each 8'3 cm. 37, 35, and 30 
 joints respectively in all 102, of which the last were 6 mm. broad 
 by 3*1 mm. long. The fourth 25 cm. bore 68 joints, with a terminal 
 length of 4*6 and a breadth of 6'6 mm. 
 
 The 5th 25 cm. bore 49 joints, of which the last were 6 '5 mm. long by 6 "3 broad. 
 
 6th 
 7th 
 8th 
 9th 
 Last 
 
 37 
 29 
 25 
 23 
 
 22 
 
 7-5 
 
 9-5 
 
 11-3 
 
 12-2 
 
 13 
 
 6-3 
 
 6 
 
 5-6 
 
 5 
 
 4-5 
 
 In all, therefore, the worm had 861 joints, but these were so different 
 in size and development, according to position, that the different parts 
 of the chain looked very different. Thus the anterior half consisted 
 of joints whose breadth was decidedly greater than their length, but 
 always decreasingly so, till about the middle of the body the joints 
 were approximately square. In the second half the length was greater 
 than the breadth, and that increasingly so, since the breadth diminished 
 in a marked manner posteriorly. By the middle of the first metre 
 the ratio of the breadth to the length was as 1 : 0*5, in the middle of 
 the last metre as 1:2. The greatest absolute breadth occurred at a 
 short distance behind the middle of the body. 
 
 We need hardly note, after what was said of Tcenia saginata 
 (p. 431), that there is a direct connection between the form of the 
 joint and the developmental stage reached by the sexual organs, and 
 
516 GROWTH AND DEVELOPMENT OF T^IXIA SOLIUM. 
 
 especially by the uterus. 1 It is evident that the joints with prepon- 
 derating breadth have either no eggs in the uterus, or but few. It is 
 in the square joints that the eggs, which accumulate in increasing 
 numbers as the uterus lengthens out, pass through their embryonic 
 development. But it is only in the extended proglottides of the last 
 metre that the eggs acquire their brown shells and the uterus its 
 final form. Only these last joints exhibit the characteristic dendritic 
 structure and colour of the uterus, which are directly evident to the 
 observer through the thin and almost transparent body -substance 
 The number of these " ripe" joints is at most about 100. 
 
 The study of the structure of the sexual organs is therefore im- 
 portant, especially in the examination of the short proglottides. Even 
 before the end of the first length of 25 cm., which includes, indeed, 
 half of the total number of joints, the sexual organs begin to appear. 
 It takes 25 to 35 cm. before they are fully formed. Then copulation 
 takes place, which is succeeded by the passage of the eggs into the 
 uterus and the beginning of the embryonic development. 
 
 In order to obtain more data for the decision of the question 
 whether these measurements and proportions have a specific or indi- 
 vidual importance, I have lately examined another well-preserved 
 specimen of Tcenia solium. The worm was somewhat more strongly 
 contracted than the one first measured, being only 175 cm. long, while 
 possessing about an equal number of joints. Before the middle of 
 the body a breadth of 7'5 mm. was attained. 
 
 The segmentation began at a distance of 3 mm. behind the head, 
 which was 1 mm. thick, but it was at first faint and difficult to de- 
 monstrate, so that I have only approximately estimated the number 
 of joints in the first centimetre at 65. The second centimetre con- 
 tained 80, the third 57, the fourth 32, and the fifth 41 altogther 414 
 in the first 5 cm., almost as many as in the other 170 cm. of the body ! 
 The small number of joints in the fourth centimetre was explained by 
 the fact that it had undergone an unusual extension, so that some of its 
 joints measured 0'3 mm., much more than in the following portion, 
 in which even those at the end did not exceed 0'2 mm. In the three 
 previous portions the length of the joints rose to 0'08, 01, and 0'17, 
 and the breadth to 0*7, 1, and 1*6 mm. respectively. The fourth much 
 extended portion showed the same breadth at its termination, the fifth 
 a breadth of 2*5 mm. Thence the size of the joints increased so 
 rapidly that the next length of 20 cm. exhibited only 229 segments, 
 
 1 We must also remember that the form of the joints is largely though here less 
 strikingly than in the very muscular Tcenia sayinata determined by the state of con- 
 traction exhibited by the worm, a fact which prevents any absolute accuracy in these 
 measurements. 
 
DIMENSIONS OF TJ5NIA SOLIUM. 517 
 
 a number which in the following lengths of 25 cm. sank to 138, 76, 
 47, 33, 26, and 22, so that the total number of segments was about 848. 
 The 229 segments, after the first 414, were so distributed that 98 
 belonged to the first 5 cm., 61 to the second equal length, and 70 to 
 the remaining 10 cm. At the end of these three portions the length 
 of the joints was 0'3, 0'9, and 1/2 mm., with a breadth of 3, 3'9, and 
 5 mm. respectively. The other relations may be best seen from the 
 following summary, to which we must add that the first 25 cm. con- 
 tain not less than 414 segments : 
 
 The 2d 25 cm. contain 1 38 joints, of which the last are 2 mm. long by 6 mm. broad. 
 3d 76 3 7'5 
 
 4th 47 
 
 5th 33 
 
 6th 26 
 
 7th 22 
 
 5 6-5 
 
 7'5 6 
 
 9-8 5 
 
 11-5 4-8 
 
 The differences seen on comparing this table with that given 
 above 1 are trifling. They lose all importance when we take into 
 account that the number of ripe proglottides in the second worm 
 is about thirty less than in the first. Thus we see here, as in 
 Tcenia saginata, that the liberation of the ripe proglottides, apart 
 from their separation in lengths, determines many individual and 
 temporary differences. On the whole, we may credit Tcenia solium 
 with about 850 joints, which is tolerably harmonious with Kiichen- 
 meister's result, who counted 825 joints in a Tcenia 5 yards 2 inches 
 long. In this calculation a portion of the neck 6 lines long is left 
 out of account, as " unsegmented." 
 
 The above-cited experiments (p. 496) show with considerable 
 exactness how long time must elapse before the first joints are libera- 
 ted. In the case observed by me, the patient voided the first joint 
 two months and a half after the introduction of the bladder-worms, 
 in the case observed by Yogt and Moulinie, the first joint appeared in 
 the course of the third month. On the basis of these observations 
 we may conclude that it requires an interval of from eleven to twelve 
 weeks to bring the development of the worm to completion . 2 Kuchen- 
 meister 3 agrees thoroughly with this, and notes that when he has suc- 
 ceeded in expelling the whole worm except the head, the return of the 
 proglottides may be certainly looked for in about ten or eleven weeks. 
 The various stages of progress within this period are unknown. I can 
 only note that in one case with which I was well acquainted, a tape- 
 
 1 By an arithmetical error in the first edition of this work, the total number of joints 
 was underrated, being stated at 749. 
 
 2 In the first edition of this work, with fewer data, I approximately estimated the 
 period at from three to three and a half months. 
 
 3 " Parasiten," second edition, p. 90. 
 
518 GROWTH AND DEVELOPMENT OF T^NIA SOLIUM. 
 
 worm 90 cm. long, with proglottides just mature, was expelled exactly 
 four weeks after an unsuccessful attempt at expulsion, which left only 
 the head remaining. 1 
 
 As to the age to which the worm may attain, we have here no 
 greater certainty than in the case of Tcenia saginata. This much, 
 however, is beyond doubt, that the hook-bearing tape-worm may per- 
 sist for a long series of years perhaps for fifteen or twenty, or even 
 /or several decennia but for how long is uncertain. In all these 
 cases, there is always the possibility that the old inmate has been 
 unconsciously replaced by a successor. 
 
 As a rule the parasitism of the worm ends by its expulsion from 
 the host in toto. Whether dead or living, it is quite the same for the 
 host, the expulsion takes place when the worm is no longer able to 
 resist the pressure of the chyle or of the intestinal muscles. We have 
 already noted in connection with Tcenia saginata that the worm may 
 under certain circumstances remain in the intestine for a while after 
 death, until it falls to pieces or becomes mummified. The worm- 
 mummy there described (Fig. 273) could be referred with some cer- 
 tainty to T. solium. 
 
 Malformations. 
 
 Malformations, properly so-called, are much less frequent in the 
 hook-bearing tape-worm (the case is different with the bladder-worm) 
 than the hookless Tcenia saginata. I have only seen one instance. 
 This was a proglottis with two symmetrical sexual openings and 
 genital ducts an abnormality which we have already noticed in T. 
 saginata (p. 471). 
 
 On the other hand, here and there, six-rayed individuals occur. 
 Krause 2 mentions a Cysticcrcus cellulosce with six suckers, found in the 
 brain of an idiot, and Zenker found on dissection of a tuberculous 
 patient fourteen immature specimens of Tcenia solium, one with six 
 suckers and twenty-eight hooks. The adherent worm, which measured 
 46 cm., corresponded in respect of the prismatic form of its proglottides, 
 and the position of the genital openings on the median ridge, with 
 the analogous malformations of T. saginata* 
 
 1 This worm showed in lengths of 25 cm. 350, 128, and 69 joints, and including the 
 last 33 joints, which occupied 15 cm., had in all 580 joints. The largest joints measured 
 5 mm. long by 4 '8 mm. broad, and were almost square, but still without embryos. The 
 gradual growth of these joints may be expressed by the ratios 1*8 : 2*5 : 3 "4 in width, to 
 2 : 3'6 : 4 in length, these being the dimensions in millimetres, both measured at the ends 
 of the first three portions of 25 cm. 
 
 2 Gottingen Nachrichten, No. 18, 1863. 
 
 3 Heller, loc. cit., p. 594 (Eng. transl., voL vii., 709). 
 
ORGANIZATION OF T^NIA SOLIUM. 519 
 
 "We will afterwards consider the malformations of the bladder- 
 worms which are specially seen in those specimens found in the brain 
 of man. 
 
 Organization of Tsenia solium. 
 
 Sommer, " Ueber den Bau und die Entwickelung der Geschlechtsorgane von Taenia 
 mediocanellata und T. solium," Zeitschr. /. wiu. ZooL, Bd. xxiv., p. 499, 1874. 
 
 The worm is distinguished not only by the size and general form 
 of its jointed body, but also by the shape and structure of its com- 
 ponent parts. Whether one examine a head or a proglottis, there can 
 be no possibility of confusing it with T. saginata. 
 
 The Eipe Proglottides, which, in contrast to those of the last species, 
 are very seldom liberated singly, present characters even more striking 
 than the head, which requires for diagnostic purposes to be examined 
 with the microscope, or at least with a lens. The flat form and the 
 small quantity of parenchyma are at once evident when we press the 
 proglottides between two glass slides and hold them against the light, 
 or when we dry them on an even surface. 
 
 It is, however, the structure of the uterus which in reality deter- 
 mines our decision, for although we have also the shortness of the 
 joints and their delicate transparent nature to help us, these charac- 
 ters are too deceptive to be implicitly relied upon. 
 
 In general, the ripe uterus of Tcenia solium, with its few lateral 
 branches, and the loose nature of its ramification, gives one the 
 impression of being somewhat reduced and spare. This is specially 
 evident on comparison with T. saginata. On the whole, the general 
 appearance is the same, in so far as we have to deal with a median 
 stem and with lateral branches. But the median stem is shorter, 
 corresponding with the shorter joint, and the lateral branches 
 are further separate, amounting hardly ever to more than nine on 
 either side, and usually only to seven. I have not observed that they 
 alternate irregularly as Sommer says. In fact they seem to me to be 
 very symmetrical, except when neighbouring branches interlace, and 
 when a lateral branch sometimes indeed every alternate one 
 becomes abortive. The interlacing of these lateral twigs is on 
 the whole much more abundant than in. T. saginata, and more 
 tree-like, so that the main branch is often turned from its trans- 
 verse direction, and the secondary branches often corne to have a 
 somewhat longitudinal course, with exception of those at the ends, 
 which are spread out like a fan. This is always the case with the 
 anteriorly directed ramifications of the principal branches, which 
 from their large size, regular distribution and shortness, exhibit 
 
520 
 
 ORGANIZATION OF T^EXIA SOLIUM. 
 
 Fio. 289. 
 
 FIG. 290. 
 
 an almost comb-like structure. The same is often noticed in the 
 distal off-shoots of the last lateral branches, but in their case this 
 structure is less striking, partly because their 
 number is more limited, and partly also be- 
 cause the associated lateral branches turn 
 aside very regularly from their transverse 
 position, and run in a curved direction towards 
 the posterior angles. Otherwise they are 
 scarcely to be distinguished from the others. 
 The space marked off by them has the form of 
 a flat, obtuse-angled triangle, and very gener- 
 ally contains at its angles the remains of the 
 shell-gland. After what has already been 
 said regarding the connection of the uterine 
 structure with the state of general organiza- 
 tion, it hardly needs to be expressly mentioned 
 that in the proglottides of T. solium the 
 ramifications of the uterus are much farther 
 from the edge posteriorly than anteriorly. The 
 transverse anastomoses of the lateral vessels 
 FIG. 289. Two segments of ii m it the further distribution of the uterine 
 
 Tcenia solium with branched 
 
 uterus. ( x 3.) 
 
 FIG. 290. Pmgiottis of 
 
 , i 
 
 branches. 
 
 Although the uterine branches are, as a rule, 
 solium with slightly w j(j er tnan j n Tccnia saginata, and are also not 
 
 branched uterus, (x 2.) 
 
 unfrequently swollen into a club-like shape, 
 
 the number of eggs contained by the joints is smaller. Thus it 
 appears that both in respect of the fertility of the individual segments 
 as well as of the general character of the chain, T. solium is far behind 
 T. saginata in its economic relations. This disparity is sometimes 
 very marked in individual specimens ; for (as is shown in the above 
 picture of a very unfruitful joint, Fig. 290) there are some tape-worms 
 whose lateral branches neither attain their normal length nor ramify 
 as usual, but remain more or less abortive. 
 
 Although Weinland asserts that he once found proglottides like 
 those depicted above in a bookless Tccnia, we may safely assume, on 
 the ground of later investigations, that they never originate from T. 
 saginata. Whenever the associated worm has been investigated, its 
 head and the formation of its joints have always proved it to be 
 Tcenia solium. 
 
 The head of the species, as has been repeatedly noted, differs from 
 that of T. saginata chiefly in the possession of a hook-apparatus ; but 
 this difference, although the most important and the most striking, is 
 by no means the only one. Other peculiarities of the species are 
 
THE STRUCTURE OF THE HEAD. 
 
 521 
 
 found in the size and form of the head. In accordance with the 
 smaller proportions of this worm, its size is considerably less (the 
 average hardly amounting to more than 1 mm.), and its form is more 
 nearly spherical, for the back of the head is more markedly contrasted 
 with the straight part of the neck, and the apex, situated on the 
 rostellum, generally projects like a dome, 0'36 mm. high. The form 
 of the apex is, however, subject to great variations, according to the 
 state of contraction of the rostellum, so that it is sometimes more or 
 
 FIG. 291. Head of Tcenia 
 solium. ( x 45.) 
 
 FIG. 292. Apical surface and circle of hooka 
 of Tcenia solium. (x 80.) 
 
 less deeply sunk in the wall of the head, and at other times elevated 
 into a conical or plug-like proboscis. After what has been already 
 noted regarding the significance of the rostellum and the motor 
 mechanism of the hooks, it is easy to see that each of these differences 
 in form is associated with a particular attitude. If the apex be re- 
 tracted, the hooks are so placed that their points are directed forwards, 
 pretty much in the longitudinal direction of the body. If the apex be 
 still more deeply sunk, the hooks sometimes come to have their points 
 resting together at a common centre. Thence, by the progressive pro- 
 trusion of the apex, they gradually become directed so far backwards, 
 that the concavity, with the now posteriorly directed points, is in 
 contact with the sides of the protruding extended proboscis. 
 
 The size of the suckers corresponds to the smaller development of 
 the head, for they only measure 0*4 to 0*5 mm. But in spite of this 
 they are generally more prominent than in T. saginata. The flattening 
 of the head is, however, less striking, for the sagittal diameter is only 
 a little less than the frontal (Fig. 292). 
 
522 ORGANIZATION OF TVENIA SOLIUM. 
 
 On a former occasion, I have described the very various positions 
 which are characteristic of the suckers of Tcenia solium (p. 513). 
 They may be moved singly or in pairs, opposite to each other, or the 
 whole four may be raised up like arms, extend in different directions, 
 and then contract. Displacements of the rostellum are generally as- 
 sociated with these movements, and indeed so constantly, that there 
 is an unmistakeable connection between these various actions. This 
 is very marked when the suckers feel about in front as though trying 
 to fix themselves to some object situated in front of the head. As 
 often as this motion takes place, the apex is observed to sink in, and 
 to remain for a time in this position, before again protruding and al- 
 lowing the hook-apparatus to unfold itself. 
 
 When we remember that this is the way in which the suckers 
 attach themselves to the wall of the intestine, and press the front 
 of the head against it, it will be seen that on the protrusion of the 
 apex the points of the hooks must press into the wall of the intestine 
 and penetrate the deeper the further they are removed from the apex ; 
 and as the apex at the same time, by the flattening of the formerly 
 cup-like rostellum, drives the points of insertion of the hooks further 
 from each other in a radial direction, the fastening is of course made all 
 the stronger, sufficient in fact to keep the body in its position without 
 the help of the suckers, and to present the necessary resistance to the 
 pressure of the chyle. 
 
 A separation may take place when the worm is not fixed too 
 deeply by a rupture of the intestinal villi, in consequence of the 
 tension exerted on the body of the worm, and thence transferred to 
 the extended hooks. It may happen, too, that the hooks straighten 
 themselves up and relax their hold of the surrounding tissue. 
 
 The manner in which the rostellum is concerned in all these pro- 
 cesses need not be again discussed, after our former remarks regarding 
 the motor mechanism of the hooks (p. 401). It is equally unneces- 
 sary to explain the structure of the rostellum and the associated 
 muscular disc, or to discuss the nature and mechanism of the suckers 
 (see p. 395). In regard to all these parts, we need only remark that 
 they do not differ in any respect from the usual conditions of the 
 cystic tape-worms. It is true that Nitsche attempted to establish 
 certain peculiarities in regard to the structure of the muscles of the 
 circlet of hooks in Tcenia solium, but this was probably due to the 
 unsatisfactory nature of his material. In reality the structure of T. 
 serrata is exactly repeated in Tcenia solium. Especially is it impos- 
 sible to regard the pouches intended for the reception of the roots 
 as a special characteristic of Tcenia solium, although they were 
 the occasion of Kiichenmeister's proposal to renounce the apparently 
 
FORM AND ARRANGEMENT OF THE HOOKS. 523 
 
 meaningless name of Solium and to call the species T. hamoloculata. 
 On the contrary such pouches are always found in the hook-bearing 
 Tcenice, for the hooks never merely project, but always have their 
 roots sunk in the external coverings of the head. After the falling 
 out of the hooks (which often takes place very soon after the removal 
 of the worm from the intestine, and especially if it be placed in 
 water), these pockets are, it is true, less distinct and striking than in 
 Tcenia solium, though this is only the case when the apical region is 
 permeated with a black pigment, as indeed it generally is. In such 
 specimens, the hook-pouches appear as gaps in the pigment, and are 
 very noticeable even on superficial examination. But, on the whole, 
 this pigmentation is less frequently observed in T. solium than in 
 T. saginata. 
 
 The Circlet of Hooks and the Hooks themselves must now receive 
 our attention. 
 
 As in the related forms (with the exception of Tcenia acanthotrias), 
 the circlet of hooks in T. solium is double (Fig. 292) : in other words, 
 although the hooks all have their points on the same circular line, 
 they do not form one, but two successive rows, one anterior to the 
 other. The hooks of the anterior row are larger than those of the 
 posterior, and are fixed to the rostellum somewhat above the 
 lateral border, so that their centre of motion is not so far from the 
 common centre as is the case with the smaller, more peripherally 
 situated hooks. Besides these differences in position, there is also a 
 slight difference in the formation of the roots, for those in front, being 
 situated on a less curved surface, have natter bases than those behind. 
 
 FIG. 293, Larger (anterior) and smaller (posterior) hooks of 
 Tcenia solium. ( x 280.) 
 
 The number of and distance between the hooks are the same in 
 both rows, and the smaller ones always occupy the spaces between the 
 larger, so that large and small hooks are in regular alternation. The 
 above-mentioned differences in the size of the hooks depend mainly 
 upon the different lengths of the posterior root-processes, which in the 
 large and small hooks have the ratio of 3:2. But these are not the 
 
52-1 ORGANIZATION OF T^NIA SOLIUM. 
 
 only differences that prevail. In the small hooks the anterior process 
 is broader at the end than in the larger ones, and is almost two-lobed 
 the claw is also shorter and narrower, and more bent at the base. 
 The considerable thickness exhibited by the basal portion of the larger 
 claw is due mainly to the fact that it is, so to speak, prolonged further 
 into the posterior process than is the case in the small hooks. To 
 this circumstance is also due in great measure the considerable length 
 of the posterior process, which has already been noticed in the hooks 
 of the anterior row. The solid portion of the process, which is 
 generally marked off from the base by a slight groove, does not 
 measure much more in the anterior hooks than in the posterior ones. 
 
 All these, however, are features which Tcenia solium shares with 
 most of the other large-hooked cystic tape-worms. Much more 
 characteristic is the above-mentioned compressed and rather stout 
 form of the hooks, which, however, can only be rightly appreciated 
 on comparison with those of related species. Another slight difference 
 is that in both small and large hooks, and especially in the latter, the 
 base of the posterior process is somewhat emarginate in the middle. 
 Certain other peculiarities, in regard to the size of the hooks, serve 
 more firmly to establish the diagnosis. The distance of the point of 
 the claw from the end of the posterior process is in the large hooks 
 0-167-0-175 mm., and in the small ones O-H-0'13 mm. (in T. serrata 
 0'25 and 0'14 mm., and in T. crassicollis 0'39 and OvlG), while the end 
 of the anterior process is about as far from the point of the claw as 
 it is from the end of the posterior root-process that is to say, O'09-O'l 
 mm. in the larger hooks, and 0'064-0-07 mm. in the small ones. 1 
 
 The number as well as the size of the hooks varies very much in 
 individual cases. The extremes are somewhat wide apart, for while 
 the smallest number is twenty-two, the largest, according to Davaine, 
 is thirty-two. Most frequently twenty-six or twenty-eight hooks are 
 found, half of them small and half of them large, so that the uneven 
 numbers seem excluded. Bladder-worms which are developed at the 
 same time beside each other appear to exhibit for the most part either 
 one or other of these two numbers. 
 
 The malformations occasionally found in the hooks have already 
 been noticed (see p. 398) ; although, as I see no special mention has 
 been made of this species, yet it was for the most part this species, or 
 rather the corresponding bladder- worm, that I had in view in making 
 
 1 Further measurements are given by Kiichenmeister (" Parasiten," first edition, p. 
 178). I omit these, because I think that the points from which the measurements are taken 
 are much too uncertain to render the size given of much value. In comparing his results 
 with the above statements, I will only mention that his measurements are in all cases 
 somewhat larger than mine. 
 
STRUCTURE OF THE PROGLOTTIDES. 525 
 
 those remarks. 1 Whether there are also adult tape-worms with mal- 
 formed hooks is doubtful, since the imperfect development of the 
 hook-apparatus would hardly permit a long enough residence in the 
 intestine to allow of the full development of the worm. 
 
 The Structure of the Joints calls for little addition to our previous 
 description, except as regards the sexual apparatus. Everything else 
 has already been mentioned in one place or other. We know, for 
 example, that Tcenia solium is far from possessing the powerful mus- 
 culature of T. saginata. We are also acquainted with the fact that 
 the four longitudinal vessels originally present are reduced to two 
 before the appearance of the sexual organs, and that they then run 
 throughout the whole length of the chain in the form of two wide 
 stems, which are always connected at the posterior border of each 
 joint by a transverse anastomosis. It is true that for a time the four 
 stems may be seen near each other, but they are no longer arranged 
 in pairs on the two flat surfaces, as in the head, but are all on the 
 same plane and close together. The change of position takes place 
 at the beginning of the neck, and is evidently caused by the marked 
 flattening of the segmented body, which no longer admits of the former 
 distribution of the vessels. In consequence of this, each of the two 
 narrow sides has an outer and an inner vessel, so arranged that 
 the vessels of the ventral female surface become the external, while 
 those of the dorsal male surface come to lie internally. It is difficult 
 to say by what influences the two inner vessels have become dwarfed, 
 but this is very probably due to the peculiarities of the position of 
 the worm. Moniez conjectures that the cause of the diminution is 
 the development of the sexual organs, which might, indeed, have some 
 effect on the adjoining parts ; but it is demonstrable that they only 
 attain their complete development at a time when these vessels have 
 already disappeared. 
 
 In regard to the calcareous corpuscles, we need only remark that 
 they are upon the whole sparsely distributed, and less marked than in 
 the related species, especially T. saginata. It appears, however, as 
 though all specimens were not alike in this respect. They also 
 exhibit many variations in size, but, as above mentioned, seldom ex- 
 ceed 0-012 mm. 
 
 The Reproductive Organs exercise a marked influence upon the 
 general form and organization of the body, just as in Tcenia saginata 
 
 1 In support of the assertion which I made at that time, that there are some bladder- 
 worms in which the circlet of hooks is not developed, I refer to the case described by 
 Lewin (Annalen des ChariU Krankenhauses, ii., p. 167 : Berlin, 1875), who found a bookless 
 bladder- worm from a pig, which possessed, instead of the rostellum, and evidently as a 
 representative of it, " an extra fifth sucker." 
 
526 
 
 ORGANIZATION OF T^XIA SOLIUM. 
 
 an influence compared with which that of the calcareous corpuscles, 
 vessels, and muscles is quite insignificant. What we have already said 
 in this respect of Tcenia saginata is true, even down to details, of T. 
 solium, which so closely agrees with it both in structure and develop- 
 ment that, with some slight alterations, the former description might 
 be adopted almost word for word. 1 Accordingly, it is unnecessary to 
 describe minutely the reproductive apparatus of this species. It will 
 be sufficient for our purpose to emphasise the differences which exist 
 between the two forms ; and in regard to any other points, to refer to 
 what was said of these organs whilst treating of T. saginata. 
 
 These differences arise in great measure from the fact, already 
 often mentioned, that in its vegetative powers Tcenia solium falls far 
 short of T. saginata. Thus, not only is the form of the uterus 
 influenced by this fact, but the whole of the reproductive apparatus. 
 
 This is especially evident from the fact that the sexually mature 
 joints of Tcenia solium are considerably smaller than those of 
 T. saginata. They exhibit hardly more than half the diameter of 
 those of the latter, being not more than 4'5 to 5 mm. in breadth, and 
 2'5 to 3 mm. in length. These differences in size of course find 
 expression also in the individual parts of the reproductive apparatus. 
 All the dimensions are smaller, the sexual pores less prominent, the 
 testes considerably fewer in number, and the csecal tubes of the yolk- 
 gland, as well as of the germ-glands, are less branched and less 
 
 compactly aggregated. Even the form 
 of the germ-glands corresponds to the 
 generally smaller space. Their longi- 
 tudinal diameter is less than in T. sagi- 
 nata, and the round discoid form of the 
 latter is exchanged for a transversely 
 oval one. This is true especially of the 
 smaller lateral lobe which lies under 
 the vagina, on the right or on the left 
 of the middle line, according to the 
 position of the genital pore. But on 
 the same side above the vagina, and 
 in the angle open in front, which the 
 descending limb forms with the 
 uterus, there is always (and not 
 merely occasionally, as I stated in 
 the first edition of this work) a group of ovarian tubules. These are 
 
 FIG. 294. Reproductive organs of 
 Tcenia solium (x 10). g.p,, genital 
 papilla; cL, cloaca. Male organs. 
 <., testes; v.d., vas deferens ; c.p. t 
 cirrhus-pouch. Female organs. ov. t 
 ovary; y.g. t yolk-gland; sh.g., shell- 
 gland; r.s., receptaculum seminis; M., 
 uterus ; d.o. , detached portions of ovary. 
 
 1 Indeed, the account given in that place of the reproductive organs of Tcenia saginata 
 was largely borrowed from the description which I gave in the first edition of this work of 
 the characters of T. solium (p. 261 et seq.). 
 
ARRANGEMENT OF THE REPRODUCTIVE ORGANS. 527 
 
 entirely absent in Tcenia saginata, and therefore furnish a very 
 welcome diagnostic characteristic for the young proglottides of T. 
 solium. The tubes are situated upon a somewhat long and slender 
 canal, which branches off, at the side of the uterus, from the common 
 transverse oviduct, and ascends in an anterior direction. According to 
 Sommer, these form a peculiar " intermediate " lobe of the ovary, but 
 I think that it is more natural, and also more in accordance with the 
 usual structure, to regard them as an isolated and separated portion of 
 the neighbouring lateral lobe. 
 
 By its depressed form and much extended sides, the yolk-gland 
 repeats the proportions of the ovary, but in consequence of its more 
 simple contour its peculiarities are less striking. 
 
 I need not dwell long upon the structure and connections of the 
 various reproductive organs. What has been said in this respect of 
 Tcenia saginata is also true of T. solium. At the most, there is only 
 a small difference between them, inasmuch as the canal connecting 
 the uterus with the shell-gland has in Tcenia solium a relatively 
 greater length ; hence the uterus appears of course still shorter. 
 
 The smaller size of the reproductive apparatus makes it quite 
 possible that its development may take place over a shorter stretch 
 of joints. Although the first rudiments of the sexual organs appear 
 in both at pretty much the same distance behind the head, or 
 about the 200th joint, the period of sexual ripeness, in so far as it is 
 announced by copulation, and by the commencement of the transfer- 
 ence of eggs into the uterus, occurs at parts of the body which are at 
 least 150 to 180 joints distant from each other. Instead of being at 
 the middle of the seventh hundred, it is in Tcenia solium in the second 
 half of the fifth hundred that the first eggs are found in the uterus. At 
 the former of these places, that is, where the sexually ripe joints were 
 found in Tcenia saginata, the eggs of T. solium have already undergone 
 a great part of their development. The ramification of the uterus 
 begins very soon after the 600th joint, while in T. saginata it only 
 appears about the middle of the eighth hundred, that is to say, at a 
 place where Tcenia solium already exhibits ripe proglottides. 
 
 The peculiarities of the processes which we have thus shortly 
 summarised are exactly the same as in T. saginata, so that it is not 
 necessary to enter into further particulars regarding them. To do 
 so would be only to repeat what has already been said (pp. 445, 446). 
 The specific peculiarities of Tcenia solium become conspicuous only 
 in the last phases, when the uterus begins to branch, and indeed find 
 expression only in the fact (Figs. 295 and 296) that the lateral 
 brandies are fewer in number. So long as the proglottides are broad 
 and short, the latter are of considerable length, and slender in form. 
 
528 
 
 ORGANIZATION OF T.EXIA SOLIUM. 
 
 At this time they are also destitute of the numerous short off-shoots, 
 which only appear when the commencing longitudinal extension 
 diminishes the transverse diameter of the worm, and when the trans- 
 verse canals begin to shorten ; and it is only at this time that the 
 formerly dichotomous brandlings assume by anastomosis the form so 
 characteristic of this species. 
 
 
 Fio. 295. Half-ripe joint of 
 Tcenia solittm. (x 2.) 
 
 Fio. 296. Half ripe joint of 
 Tosnia taginata. ( x 2.) 
 
 What I have observed regarding the embryonic development of 
 Tcenia solium is in close correspondence with that of the related forms. 
 In the half-ripe eggs, besides the embryo, or the ball of cells which 
 becomes changed into it, there are three large nucleated cells, with 
 granular masses filling up the interspaces between them. These 
 structures are enclosed along with the embryo in an envelope, which 
 is often tailed, and are still to be found when the embryo has become 
 surrounded by its shell. Afterwards most of the cells are destroyed, 
 so that there only remains within the shell-bearing embryo a viscid 
 fluid abounding in granules. This reminds one somewhat of the 
 albumen of a bird's egg, and, like it, is surrounded by a kind of shell, 
 
 namely, the enveloping membrane. But 
 in the ripe proglottides both the albumen 
 and membrane have generally disappeared, 
 or rather have been resolved into a pulpy 
 substance, which, along with the shell- 
 bearing embryos, form the so-called " eggs 
 e of the proglottides," which fill the interior 
 vitelline membrane. ( x 450.) o f the uterus. The shell of the embryo is, 
 as in Tcenia saginata, thick and firm, of a brownish colour, and 
 covered with countless little rods, but of a rounder shape. Its 
 diameter amounts to 0'03 mm., while that of the simple embryo is 
 not more than 0'02 mm. 
 
OCCURRENCE OF THE ADULT TAPE- WORM. 529 
 
 Occurrence and Medical Significance. 
 1. The Adult Tape-Worm. 
 
 As is well known, Tcenia solium is one of the intestinal worms 
 which are found exclusively in man. Von Siebold certainly asserts 
 that he reared tape -worms from the Cystwercus celluloses of the 
 dog, 1 but as he (with Pallas and other older helminthologists) 
 regarded the human tape-worm as identical with the cystic tape- 
 worms of the dog, his results are of course no longer valid. 2 Other 
 investigators, who knew how to distinguish Tcenia solium from the 
 large-hooked tape-worms of the dog, have never succeeded in rearing 
 the bladder-worm of the pig in the intestine of the dog, although such 
 investigators as Haubner, Kiichenmeister, Heller, and myself made 
 experiments on a considerable number of these animals. Just as little 
 success has attended experiments with other mammals, such as pigs 
 and martens (Leuckart), cats, rabbits, guinea-pigs, and apes (Heller). 
 
 Of course, even in man, every bladder-worm does not grow into a 
 tape-worm, nor even every one of those that enters the stomach unin- 
 jured that is to say, with uninjured head. Ktichenmeister estimates 
 the loss in the above-mentioned cases at about 50 per cent., but this 
 estimate has only an uncertain value, since the result must vary much 
 in different cases, both with the more or less thorough mastication and 
 with the nature of the gastric juice. 
 
 The hypothesis of a special predisposition to the tape-worm, which 
 was formerly held on the ground of certain statistical facts, is now 
 abandoned. In every case the occurrence of Tcenia solium depends 
 upon a further development of the Cysticercus cellulosce. Whenever 
 the latter gets into the human intestine in a condition capable of 
 development, there is not only the possibility, but the probability, of 
 this further development, and this is quite independent* of the age or 
 sex of the individual who is infected. The frequency of the worm 
 is always determined by the opportunities given for this reception, 
 and will increase, of course, in proportion as it is favoured and facili- 
 tated by the habits and mode of life. 
 
 As might be supposed from such a state of affairs, Tcenia solium 
 always occurs where the pig is reared and eaten as a domestic animal, 
 and is most frequent where (ceteris paribus) the breeding of pigs is 
 most common. So that Tcenia solium is probably, like T. saginata, 
 cosmopolitan. It is, however, doubtful whether it is so universally 
 
 1 " Band- und Blasenwurmer," p. 87. 
 
 2 This explains the great dissimilarity, in v. Siebold's case, between the administered 
 bladder-worms and the tape-worms which he afterwards found, a fact which even at 
 that time gave rise to the conviction that the dog was but little adapted for rearing 
 the bladder- worms of the pig. 
 
 ? L 
 
530 OCCURRENCE AND RESULTS OF TCENIA SOLIUM. 
 
 and regularly distributed as the latter ; for the pig is not only on the 
 whole a much less common source of food than the ox, but in many 
 countries, and expecially in those of the Torrid Zone, it is either never 
 or only occasionally and exceptionally eaten. I may recall in this 
 connection the Abyssinians, who loathe swine's flesh, and are therefore 
 exempt from Tcenia solium that is to say, from Eudolphi's hook- 
 bearing form. 
 
 Owing to the confusion which has prevailed until our own day 
 regarding the diagnosis and nomenclature of the two chief tape-worms 
 found in man, it is impossible to determine rigidly their range of 
 distribution. But it is at least certain that Tcenia solium is found, not 
 only in Europe and in North America, 1 but in Australia, India, Turke- 
 stan, and Japan, although in the last-named localities (in Japan, accord- 
 ing to a communication of Prof. Baelz in Tokio, and in Turkestan, 
 according to Fedschenko) it is much less frequent than T. saginata. 
 Even in Europe it is well known that there are many countries (p. 480) 
 in which T. saginata predominates, while others are more infested 
 by T. solium. So far as we know, the latter is most frequent in 
 certain districts of England and Germany such as Thuringia, Saxony, 
 Brunswick (" around the Harz," as Goze has remarked), Westphalia, 
 Hesse, 3 and Wiirttemberg, in all of which the breeding of pigs 
 is common, and much pork is consumed. As we have already men- 
 tioned, its occurrence has of late, according to all appearance, been 
 much less frequent. In Leipzig, for example, where Tcenia solium 
 used to be frequently observed, it is now difficult to find a specimen 
 of it ; and Krabbe writes to me that in Denmark the per-centage has, 
 within the last ten years, diminished from 53 to 20. I need hardly 
 add that this decrease is a triumphant result of our helminthological 
 investigations. The relations of Tcenia solium to the Cysticercus cellu- 
 losce have become more widely known, and the flesh of the pig, which 
 also harbours Trichina, is more carefully inspected, and less frequently 
 
 1 Regarding the occurrence of Tcenia solium in North America (among negroes and 
 white people), see Weinland, "Tape-Worms of Man," p. 39 : Cambridge, U.S.A., 1858. 
 
 2 Of fifty-seven cases of tape-worms in Giessen known to me during the first year of 
 the seventh decade of this century, forty-five were Tcenia solium. Miiller also reports in his 
 " Statistik der menschlichen Entozoen" (see p. 151) that of twelve cases of tape-worm found 
 in the hospital at Dresden, ten were due to this worm, and in Erlangen only seven out of ten. 
 For the sake of comparison, I may add that Krabbe in Copenhagen found T. solium fifty- 
 three times out of a hundred cases, Giacornini in Turin four times out of eight, Grassi in Milan 
 three times out of twenty-five cases, and Marchi in Turin once out of thirty-five. Tcenia 
 solium is thus much less frequent in Italy than in the middle and north of Europe ; but 
 of course this does not exclude the possibility of its being found in greater numbers in par- 
 ticular places. Sangalli, for example, reports that this is the case in Rome. Regarding 
 the occurrence of the tape- worm in Italy, see Grassi " Contribut. allo stud, dell' p]lmin- 
 tolog.," Gaz. med. Ital.-Lomb., t. i., p. 4, 1879 ; and for Krabbe's reports, see his Uyeskrift 
 for Laeger, Bd. vii., No. 7, 1869. 
 
POSSIBLE MODES OF INFECTION. 531 
 
 eaten raw, and all this has tended to restrict the frequency of the 
 tape-worm. For the calculation of the per-centage we can only rely 
 upon the reports of Mliller, according to which Tcenin solium was 
 found nineteen times in 3814 post-mortem examinations (in Dresden 
 and Erlangen) that is, about once in 200 examinations, or 0'5 per 
 cent. In Dresden its occurrence was somewhat more frequent than 
 in Erlangen. 
 
 After what we have said on a former occasion regarding the trans- 
 ference of Tcenia saginata, it is easy to see that the occurrence of 
 T. solium is by no means exclusively determined by the consumption 
 of flesh, but quite as much, and indeed almost more, by the condition 
 and preparation of the meat. And the more frequently the latter is 
 eaten in a raw or half-raw condition, in consequence of local or 
 individual custom, the more does the danger of infection increase. 
 
 It is true that, upon the whole, pork is much less frequently eaten 
 raw than beef, and that it is also less frequently ordered for dietetic 
 purposes ; but in certain districts, and especially where there is a large 
 manufacturing population, it is a favourite dish in the form of mince- 
 meat, which is merely salted and peppered. Speculative butchers 
 even prepare this mince-meat from measly flesh, which thus loses its 
 suspicious appearance, but almost none of its danger ; for, as we have 
 seen (p. 382), the bladder-worm heads are alone sufficient to transmit 
 the tape- worm. 
 
 For the same reason, the prepared meats bought in small portions 
 in butchers' shops (and particularly sausages and ham) are by no 
 means so harmless as at first appears. They probably often form the 
 vehicle of Tcenia solium, and all the more so, since butchers are accus- 
 tomed to remove the free-lying bladder-worms with the knife, and 
 perhaps with the very same one which is afterwards used to chop up 
 the meat. 
 
 Further, when we consider the great adhesiveness possessed by the 
 bladder- worms and their heads, on account of the damp nature of their 
 surface, it will be seen that the 'possibility of a transference is by no 
 means limited to such a case. The possibility is always present 
 wherever raw pork is stored, and the transmission may be effected by 
 the most manifold objects, and that all the more easily since, as is 
 well known, the bladder-worm of the pig is found very frequently, 
 and usually in great numbers. Nor are the worms transferred in food 
 only. Under some circumstances, even the hand is quite sufficient, 
 especially since, to quote the common saying, there is but a short road 
 from it to the mouth. Cases have even been heard of in which not 
 only children, but even adults, have picked up and swallowed single 
 bladder-worms in the kitchen. 
 
532 OCCURRENCE AND RESULTS OF T^NIA SOLIUM. 
 
 But it is not necessary to quote these cases of perverse gluttony 
 in order to prove that the bladder-worms of raw pork, just like those 
 of beef, frequently find an entrance into man and produce the tape- 
 worm. Statistics also abundantly show that those persons whose 
 position and vocation oblige them to handle raw meat, or to taste 
 little portions before it is perfectly cooked, are as often afflicted by 
 Tcenia solium as by T. saginata. 1 Of Krabbe's fifty-three cases no 
 fewer than forty-two belonged to the female sex, and only eleven to 
 the male. 2 The occupation and position of these persons could not 
 always be ascertained, but so far as it was possible to do so, it ap- 
 peared that half of the female patients were housemaids and kitchen- 
 maids. So far as the age could be learned, three-fourths of all the 
 patients were between twenty and forty. In children under ten (and 
 Krabbe observed the worm even in some three or four years of age) 
 the two sexes seemed equally liable. 
 
 The circumstance that Krabbe's lists contain a relatively large 
 number of Germans, is explained by the author in a letter to be due 
 to the fact that the latter, even in foreign countries, adhere to their 
 custom of eating raw flesh and fresh sausage, and of usually procuring 
 the latter in small quantities from the butcher's shop. The same is 
 asserted of the Germans in Paris, among whom the tape-worm also 
 seems to occur with unusual frequency. 3 
 
 The counterpart to this is furnished by the fact that among thirty- 
 five Tocnice which Marchi collected in Florence within a certain time, 
 he only found a single T. solium, although during that time no fewer 
 than 13,000 measly swine had been imported and eaten. 4 
 
 The almost entire immunity of the inhabitants of Florence from T. 
 solium is due, as is shown by Pellizzari, to the circumstance that with 
 them pork is never eaten raw like beef (from which they get Tcenia 
 saginatd), but is always carefully cooked. By cooking the bladder- 
 worms are almost sure to be killed, and at any rate much more fre- 
 quently and thoroughly than the Trichinae, which, as is well-known, 
 only die at a temperature of about 60 C. (140 F.), while the former 
 generally perish at 47 C. and 48, and hardly ever survive 49 
 (120 F.). 
 
 1 The similarity of the conditions of infection also explains the fact that both kinds of 
 tape-worms not unfrequently occur at the same time in the same individual. Such cases 
 have been observed by Krabbe, Miiller, and Heller ; by the latter in a butcher. 
 
 2 M tiller's reports, notwithstanding the small number of cases, also leave no doubt 
 that Tcenia solium is more frequent in women than in men. 
 
 3 Lancereaux, Arch. g6n6r. mtd., t. xx., p. 553. 
 
 * Pellizzari and Cobbold, "Parasiti interni degli Animali domestic!," Trad, dal 
 Tommasi, Append., p. 172. On the authority of this, Kiichenmeister states that 13,000 
 kilos of measly pork are consumed yearly in Florence. 
 
EFFECT OF TEMPERATURE ON THE BLADDER- WORMS. 533 
 
 The most thorough investigations regarding the power of resistance 
 of the bladder-worms of the pig are due to Perroncito. Although at 
 first inclined to the opinion that it required a temperature of at least 
 125 C. (257 F.) to render the bladder-worms harmless, 1 he was after- 
 wards enabled, by means of a more exact method of investigation, to 
 establish that the latter are certainly killed when the temperature of 
 the surrounding fluid reaches 50 C., or even below that, and when the 
 worms remain in it longer than a minute. 2 What impelled Perron- 
 cito to these renewed researches was the opposition to his first results 
 on the part of Pellizzari, who, like Lewis and Cobbold, had fixed the 
 fatal temperature at about 60 C. 
 
 The difference between these results is explained in this way, that' 
 the experiments on which they are founded were made sometimes on 
 large masses of flesh, sometimes on the isolated bladder-worms, where 
 the surrounding temperature would of course affect the actual objects 
 with varying rapidity and completeness. 
 
 To fix the absolute power of resistance possessed by the bladder- 
 worms, it is best to take the isolated worms, as Perroncito did in his 
 later experiments. He placed them on Schultze's warm stage, and 
 observed the effects of increasing warmth. While the bladder-worms 
 at low temperatures (under 16 to 20 C.) usually remain motionless, 
 after passing above 30 to 35 C., more or less lively contractions of the 
 body as a whole, and particularly of the suckers and proboscis, are 
 observed. The movements become still more energetic at a tempera- 
 ture of 42 to 45 C., but then suddenly stop, in some cases at 45 C. 
 or 46 C., or only at 48 C., and do not begin again even if the 
 worm be gradually cooled down to the temperature of the air, and 
 allowed to rise again. Only in one case did a Cysticercus survive a 
 temperature of 49 C. ; but it became motionless at 50 C. 
 
 Perroncito showed distinctly that the motionless state is in reality 
 death, not only by the use of the warm stage, 3 but by proving experi- 
 mentally " that such overheated bladder-worms had lost their power 
 of development." One of his students, a young Dr. M., swallowed on 
 two different occasions (January and March) a bladder-worm which 
 had been thus heated up to 50 C., and remained free from tape- 
 worm. 4 
 
 In order to ensure the death of the bladder- worm in cooking, a 
 
 1 "Delia panicatura degli animali," Ann. R. Accad. Agricdt. Torino, t. xv., 1872. 
 
 2 " Sulla tenacita di vita del Cysticerco della cellulosa," ibid., t. xxx., 1876 (abridged 
 in Moleschott's Unters. zur Naturlehre, Bd. ix., No. 37), and "Delia grandine e panicu- 
 latura nelT uomo e negli animali," ibid., t. xix. 
 
 3 The attempt to prove death by the "inhibition method" yielded but doubtful 
 results, so that we may omit it. 
 
 4 " Sulla tenacita, &c.," p. 21. 
 
534 OCCURRENCE AND RESULTS OF TJENIA SOLIUM. 
 
 higher temperature and a longer exposure to it are necessary. The 
 flesh must be boiled or roasted till it is " done through and through." 
 No bladder-worm can survive the coagulation of the surrounding 
 albumen, or the decolor isation of the blood, but half -cooked flesh 
 contains numerous living bladder-worms. 
 
 The process of smoking and pickling, if rightly conducted, may 
 also render the bladder-worm harmless. Weinland, indeed, speaks of 
 a rumour current in Boston that the English soldiers during the 
 Crimean war rejected the cured ham sent them from home, since it 
 infected them with tape-worm ; but this is contradicted by the fact 
 that the bladder- worms can hardly survive the death of their host 
 more than a few weeks. 1 
 
 As to ham properly prepared from measly flesh, my experiments, 
 which were detailed in the first edition of this work, and which 
 were the first on the subject, have proved its harmlessness. As I 
 then pointed out, the fluid in the bladder gradually disappears by 
 evaporation during the smoking. The body collapses, and, after a 
 short time, acquires, like the head, a turbid character. Even in fresh 
 ham, bladder-worms so altered never exhibited any symptom of life, 
 even when I transferred them into the stomach of a newly killed 
 animal, and surrounded them with the moist warmth of the incubating 
 apparatus. This was equally unsuccessful in the case of older ham, 
 in which the bladder-worms had shrivelled up into knots of the size 
 of a large pin-head. 
 
 Kiichenmeister arrived at similar results in the experiments which 
 he has lately conducted along with Siedamgrotzky in the Dresden 
 Veterinary College, but their cogency is weakened, inasmuch as the 
 measly flesh (cured and smoked) was given to a dog, an animal not 
 specially adapted to prove the vitality and developmental potency of 
 bladder-worms from the pig. 
 
 Not only culinary treatment, but also decomposition of the flesh, 
 soon puts an end to the life of the bladder-worm. In midsummer I 
 have seen the bladders becoming flabby and turbid in eight days, 
 while in autumn and winter they were alive and in motion (in moist 
 warmth) after I had kept the measly flesh fourteen days in a space 
 secured from frost, at a temperature of from 5 to 8 C. 
 
 Although the danger of infection by food prepared from pork is 
 thus on the whole but slight, yet it cannot be denied that the popular 
 methods do not always ensure the death of the inmates. This is 
 especially the case with those dishes, such as cutlets and sausages, 
 which are rapidly prepared. Such dishes serve to explain the presence 
 of tape-worms in persons who have certainly never eaten raw meat. 
 
 1 "Tape-Worms of Man," p. 36. 
 
MULTIPLE OCCURRENCE IX ONE HOST. 535 
 
 The occurrence of the bladder-worm in groups explains how the 
 presence of several specimens of the Tamia solium within one host is 
 much more frequent than was the case with T. saginata (the " ver 
 solitaire"). Two or three of the former often live together in the 
 same intestine, and from six to ten specimens are not uncommon. 
 Sometimes the number is still greater, 1 as is proved by the cases of 
 Kybuss, who within eight hours expelled twenty-five tape-worms 
 from one patient ; of Heller, who disentangled twenty-eight individuals 
 from an expelled ball of tape-worms ; and of Kleefeld, who actually 
 observed forty-one chains existing simultaneously within one in- 
 dividual. The last subject had, it is expressly noted, eaten raw pork 
 daily for four years, and had not even rejected what was measly. 2 
 Similarly Kiichenmeister reports the case of a man who voided thirty- 
 three Tcenice at once. He was, as Kiichenmeister remarks, "the 
 sweetheart of a butcher's daughter, and often got bladder-worms to 
 swallow from his love." I myself knew a case of a hysterical woman, 
 who was ordered to eat raw flesh for dietetic reasons, and who 
 expelled seventeen tape-worms on two occasions within eight days. 
 
 Jews, who eat no flesh of swine, of course remain free from Tcenia 
 solium, but are hardly less infested with T. saginata than their 
 Christian neighbours. 
 
 With regard to the length of life and position of the worm, and with 
 regard to the disorders due to its presence in the intestine, it is 
 perhaps enough to refer to what we have already said about T. 
 saginata. This difference ought, however, to be noted, that the 
 phenomena of intestinal irritation, and the resulting nutritive and 
 nervous disturbances, are very much less intense in T. solium than in 
 the case of T. saginata. 3 We may, indeed, infer this from the fact 
 that T. solium not only grows more slowly, and is as a whole not only 
 shorter, but also much less muscular, and, therefore, that by its con- 
 tractions the intestinal mucous membrane and its villi are less fre- 
 quently and less intensely irritated. On the other hand, T. solium 
 has, of course, in its circlet of hooks a weapon which is probably not 
 without importance from a medical point of view. We know, indeed, 
 
 1 I must leave it undecided whether Gmelin's report of finding 200 tape-worms 
 together in one host is really based on fact (Linn., "Syst. nat.," ed. xiii., t. i., p. 6, 
 p. 306). 
 
 2 Deutsche KliniTc, No. 16, 1853. 
 
 5 Lewin has lately (Ann. d. Charite-Krarikenhauses, p. 656, Th. ii., Berlin, 1875) 
 asserted that the frequent disturbances of the nervous respiratory and circulatory functions 
 occurring in tape-worm patients are not due to the tape-worm, but to the Cysticerci 
 which likewise occur. But he forgets that these phenomena are much more constant 
 and striking in the case of Tcenia saginata, which has never yet been observed in the 
 Cysticercoid state in man. 
 
536 OCCUREENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 that by means of this weapon the worm may penetrate the intestine 
 of its host, and thus occasion injuries which may under certain circum- 
 stances cause ulceration, and similar pathological conditions. 
 
 It is, however, only in its immediate effect on the intestine that 
 one T. solium is of less account than one T. saginata. But T. solium 
 very frequently occurs not solitary, but associated with several or even 
 with many companions, and this very materially alters the state of 
 the case, for not only is the irritation of the intestine and the loss of 
 nutritive juice increased, but the adjacent worms occasion frequent 
 movements by their mutual contact and pressure, and also roll them- 
 selves up into a ball. 
 
 In estimating the clinical importance of T. solium, we have to do 
 not only with the troubles above referred to, but also with the fact 
 that the embryos may develop within the human body as well as 
 within the pig, and may thus, according to their position, occasion 
 diverse pathological states, aud may often endanger even the life of 
 their host. Since the bladder-worms of T. saginata have never been 
 found as yet in man, we must concede that, in spite of the probably 
 less intense intestinal irritation, T. solium is by far the more 
 dangerous species. The proglottides and eg^s voided by the patient 
 endanger not only his own health, but also that of his neighbours, so 
 that the removal of the unwelcome guest is a pressing necessity. It 
 would, indeed, be justifiable to have a sanitary law to the effect that 
 the worm should be at once expelled, for the host is a source of 
 danger to the community. 
 
 2. The Bladder- Worm. 
 
 Stich, " Ueber das Finnigsein lebender Menschen," A nnalen des ChariU-Krankenhauscs, 
 Jahrg. iv. f p. 154 : Berlin, 1853. 
 
 Lewin, " Ueber Cysticercus cellulosse und sein Vorkommen in der Haut des Menschen," 
 Annalen des CkariM-Ki'ankenhauses, Jahrg. ii., p. 609 : Berlin, 1875. 
 
 Davaine, "Trait6 des entozoaires, &c.," second edition, p. 667 : Paris, 1860. 
 
 We have already noted (p. 511) that the disease caused by 
 bladder-worms has been known for centuries. Apparently, indeed, the 
 knowledge of these forms dates from remote prehistoric times, for the 
 first mention of the bladder-worms of the pig (in the " Knights " of 
 Aristophanes) refers to the then existing custom of examining the 
 tongue of the pig, in order to detect the presence of the so-called 
 ^aXafat (grandines). Under these circumstances, the supposition 
 seems not improbable that the prohibition of swine's flesh among Jews 
 and other Oriental peoples had for the most part reference to the 
 presence of bladder-worms. 
 
HISTORICAL ACCOUNT OF CYSTICEECUS CELLULOSE. 537 
 
 We know, however, that the animal nature of the bladder-worms 
 was not detected till towards the end of the seventeenth century, nor 
 was it generally recognised till at a still later date (in consequence of 
 the researches of 0. Fabricius and Goze). Till then the bladder-worms 
 were regarded as tumours, closely allied to the encysted and glandular 
 tumours. In Oribasius and Aetius we find it stated that Androsthenes 
 compared them to tubercles, and that Aretseus compared measly pigs 
 to people suffering from elephantiasis. The fact, known even in 
 Aristotle's day, that new-born pigs had no bladder-worms, seemed 
 quite to harmonise with the theory which sought to explain these 
 structures as diseases. 
 
 Our knowledge of bladder-worms did not, however, attain any 
 completeness till the genetic relation between them and T. solium was 
 demonstrated. Then for the first time it was seen that the bladder- 
 worm disease, which had been formerly referred to bad food, such 
 as decomposing corn or acorns, or to infection and inheritance from 
 one pig to another, always originated from infection with the eggs of 
 the common hook -bearing tape-worm infesting man. Such an infec- 
 tion is greatly facilitated by the habits of the pig, which rejects neither 
 human excrement nor water from the dung-heap, and by the fact 
 that the joints of T. solium are always expelled with the faeces, 
 and sometimes hang together in numbers even after expulsion. 
 Thus it is explained that the bladder-worms of the pig are only rarely 
 found isolated, but usually live in companies, and sometimes in such 
 numbers that the flesh looks almost like frog's spawn. In the case of 
 an animal experimented on by Haubner, there were in one piece of 
 flesh about 17 grams in weight not fewer than 133 bladder- worms, 
 so that, supposing the distribution uniform, the total number present 
 in a mass of flesh weighing 20 pounds would be about 80,000. I 
 obtained similar results from one of my experiments, in which I 
 counted 250 bladder- worms in about 31 grams of flesh. 
 
 Cases of such abundant infection are of course rarer in nature 
 than in experiment, but some might be cited where 15 grams of 
 flesh contained about 30-40 bladder- worms, and where the total 
 number of parasites might be estimated at from 12,000 to 20,000. 
 The favourite situations of the worms are the breast and shoulder 
 muscles, the tongue, the diaphragm, and the legs. The gullet, heart, 
 and the subcutaneous tissue are also frequently inhabitated by 
 bladder-worms, as are also the nervous centres and eyes, while the 
 viscera are, as a rule, only rarely infested. 
 
 The symptoms of disease vary according to the situation and 
 number of the bladder- worms. When they occur but sparsely, and 
 are restricted to the muscles, they occasion hardly any disturbance. 
 
538 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSJE. 
 
 In such cases they may be perceived even during life when they 
 occur on the under surface of the tongue or inside the eyelids. But 
 even in cases of abundant infection the worm is by no means always 
 recognisable with certainty. Hoarseness and falling out of the 
 bristles are indeed common, but they are neither certain nor constant, 
 and are apparently only present when the laryngeal muscles and sub- 
 cutaneous tissue are penetrated by the parasites. In extreme cases 
 they produce a definite cachexia, which, in consequence of continued 
 and aggravated disturbance of the nutrition, may finally end in 
 death. When an excessive number of bladder-worms infests the 
 bodies of swine, they become, according to Zlirn, 1 dull and melan- 
 cholic. They no longer curl their tails, but show pale proboscides 
 and colourless mucous membrane in the mouth. They cease to take 
 their food, so that marked emaciation sets in. The mouth has a bad 
 smell, and on the neck, head, and shoulders cedematous swellings 
 appear. The bristles fall off still more readily, and exhibit usually, 
 as Aristotle observed, bloody lower ends. The weakness increases 
 greatly, and leads to a paralysis of one or other of the extremities, 
 and usually to a distinct paraplegia. The emaciation gradually 
 increases, and the grunt becomes almost a croak. Then diarrhoea 
 sets in, which increases the stink, and this continues usually till the 
 death of the animal puts an end to its sufferings. When the bladder- 
 worms occur in the brain, then one observes, in addition, cramp, 
 madness, or paralysis. 
 
 When the disease is but slight, then the flesh is normal in appear- 
 ance, apart from the presence of the embedded worms, but in extreme 
 cases, and especially in fatal ones, the flesh appears pale and dis- 
 coloured, and infiltrated with serum, which flows out in little streams 
 when putrefaction begins. 
 
 These complex symptoms of bladder-worm disease cannot be 
 likened to the acute Cestode tuberculosis, which we saw in the ox 
 after infection with Tccnia saginata, either in respect of symptoms 
 or of efficient factors. The latter consists essentially in the reaction of 
 the organism against the imported Cestode brood, while the bladder- 
 worm disease is rather the consequence of the pressure exerted by the 
 parasites on their surroundings. The phenomena of acute Cestode 
 tuberculosis do not occur in the pig even after abundant introduction 
 of germs. Gerlach, indeed, reports the case of two young pigs which 
 died after a lapse in the one case of nine, and in the other of twenty 
 days, after feeding with T. solium, and that with more or less distinct 
 symptoms of intestinal inflammation, and is therefore inclined to 
 suppose that an abundant importation of tape- worm eggs may be fatal, 
 
 1 " Schmarotzer der Haussaugethiere," Bd. L, p. 137. 
 
PATHOLOGICAL RESULTS OF THE BLADDEE-WOIIM. 539 
 
 through inflammation heing set up in the wall of the intestine and in 
 other organs. 1 There is, however, no proof of the correctness of this 
 supposed connection of cause and effect. Other investigators have 
 always succeeded in keeping their animals alive, and free from any 
 pathological symptoms, when fed repeatedly with long chains of 
 proglottides, even though they experimented with young pigs, which, 
 according to Gerlach (p. 495), are alone suited for the development of 
 the "bladder-worms. The fact that the young bladder-worms lie at 
 first almost free, and only gradually form a firm capsule, while those 
 in the ox have from the first a thick sheath of exuded lymph, is 
 certainly not in favour of the idea that the pig reacts against the 
 invading brood as strongly as does the ox. We need hardly note 
 that this is very important, for the pig, from its mode of life, is much 
 more frequently infected than the ox. 
 
 The genetic relation between the bladder-worm and Tcenia solium 
 makes it evident that its occurrence and frequency in various districts 
 must be very varied. But it is not the distribution and frequency 
 of the tape-worm which alone determine this, for it depends still 
 more, perhaps, on the condition and housing of the swine. Where 
 the swine are bred in a half-wild state, being generally driven out to 
 the meadows or the oak-woods, where they have to seek their own 
 food, then their opportunities of infection are more frequent than 
 when they are kept and fed in the styes. In fact, the introduction 
 of the custom of feeding in the stye has in many cases markedly 
 reduced the frequency of Cysticercoid disease. This can of course be 
 hoped for only when the pigs are kept in a cleanly way, and not allowed 
 to get near dung-heaps or privies, which are always to a certain ex- 
 tent dangerous. Their food must of course be freed from all possible 
 contact with human excrement. Particularly must any tape-worm 
 patient be removed as rapidly as possible from near the swine, 
 since his presence is a source of danger to the whole herd. This is 
 strikingly illustrated by an observation made by Fiirstenberg, 2 which 
 tells us of a tape- worm patient who once infected a whole herd of 
 fifteen pigs, which had broken through the barrier separating them 
 from the privy. Two of the number exhibited an acute affection, 
 which was designated Cestode tuberculosis with doubtful accuracy, 
 and the others were rendered quite useless. 
 
 Since human excrement is deposited in very varied places where- 
 ever man exists, it is readily conceivable that wild swine may also be 
 occasionally infected, but this is rare, as one would expect in the 
 case of animals living far from the dwellings of man. 
 
 1 Loc. cit., p. 68. 
 
 2 Hosier, Archivf. pathol. Anat., Bd. xxii?., p. 426, 1862. 
 
540 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 It is quite different, however, in the case of the Indian swine, as 
 we have learned from English physicians stationed in the Punjab. 
 The half- wild animals round the villages are specially fond of 
 frequenting the public dung-heaps, to which we have already referred 
 in connection with the bladder-worms of the ox (p. 473). Day after 
 day, according to Flemming, 1 they may be seen on the look-out, 
 waiting till the natives finish operations. They hardly give them time 
 to do so, and have sometimes to be driven off by force. Since Twnia 
 solium is hardly less common in India than T. saginata, it is readily 
 seen that the bladder- worms of the pig must also be excessively 
 common. 
 
 Similar circumstances give rise to similar consequences. Thus 
 we understand why in Ireland, Slavonia, and certain parts of North 
 America, the bladder-worms of the pig are of the commonest 
 occurrence. 
 
 In Germany, too, and in Central Europe, there are localities where 
 the swine are so frequently and so abundantly infected with bladder- 
 worms that they have quite a bad reputation with dealers and butchers. 2 
 These are mostly country districts, where the excrement of the in- 
 habitants is carelessly deposited, and is easily accessible to the swine. 
 Villages furnish a larger contingent of measly swine than do towns, 
 though the latter afford more instances of tape- worm patients, owing 
 to the greater consumption of flesh, or rather owing to the immense 
 number of animals imported from the country for town consumption. 
 
 Although these facts are generally known, we have but few 
 satisfactory data as to the occurrence of bladder-worms, much 
 fewer than in the case of Ti-ichina. The former, though occurring 
 more abundantly, have less hygienic importance, since, from their 
 demonstrable size, they involve less danger than do the others, which 
 have a rarer and more hidden occurrence. 
 
 Out of 1,728,600 swine examined in 1876 in Prussia, there were, 
 according to the newspaper reports, 4706 infected with bladder-worm, 
 i.e., 1 for every 370. Similarly, in Vienna 3 there were in about 
 10,000 swine 163 infected (1'307), in the Cassel district, 4 out of 
 149,500 examined in 1872-74, there were only 158 " measly," or 1'945. 
 This last ratio can hardly be directly compared with the former, since 
 the less serious cases were probably unnoticed. Within a certain 
 range one finds marked divergences, as may be best seen perhaps 
 
 1 Cobbold, "Parasiti interni, &c.," p. 46. 
 
 2 Thus von Siebold notes in his " Band- nnd Blasenwiirmer " (p. T14) that the swine 
 imported into Neufchatel from the surrounding country are almost all "measly," while 
 such a disease is almost unknown in the west of Switzerland. 
 
 3 Oesterr. Monatschr.f. Thierheilk., No. 2, p. 14, 1876. 
 
 * Vierteljahnschrift f. gerichtl. Medicin, Bd. xxv., p. 202. 
 
FREQUENCY OF ITS OCCURRENCE. 541 
 
 from a communication of Hosier's, 1 according to which there were in 
 20,000 swine only 9 markedly infested with bladder-worms (1 : 2222), 
 although every eighth animal harboured a few Cysticerci. It is, 
 indeed, possible that the bladder- worms which were abundantly found 
 in the omentum and viscera did not exclusively belong to Cysticercus 
 cellulosce, but I think, from the results of my experience in Giessen 
 in the year 1860, that we may conclude that there are districts in 
 Germany in which 23 per cent, of the swine are infected with 
 bladder -worms in varying numbers. 
 
 Eeports from Italy tell the same story. Pellizzari estimates the 
 number of specially measly swine at 3-4 among 11,000-12,000 (one for 
 every 3000-4000), while Perroncito 2 reports that, according to the 
 statement of an official inspector (Langueyeurs), one diseased specimen 
 for every 250 occurs in Turin, while in Milan (according to a calculation 
 based upon three months) 80 were found in 5500, or one in seventy. 
 
 However imperfect these statistical results may be, this much is 
 certain, that Cysticercus celluloses in the pig is by no means rare, and, 
 indeed, is far more abundant than Trichina. 3 
 
 This is not only true in regard to the pig, but also, as we have 
 recently learned from the computations of Mtiller 4 and Dressel, 5 for 
 man. The various results are conflicting, even those of the same authors 
 varying when they have observed in different localities, so that we 
 are perhaps justified in believing that the occurrence of the Cysticercus 
 is as much determined by local conditions as is the occurrence of the 
 Tcenia; at all events the reports seem to agree in establishing a 
 diminution in the frequency of the bladder-worm. 
 
 If one calculate from the existing data as contributed by the 
 Pathological Institutes of Berlin (Virchow), Gottingen (Fb'rster), 
 Dresden (Zenker), and Erlangen (Zenker), one finds in a total of 
 9753 post-mortem examinations 127 cases of Cysticercus cellulosce^ 
 or 1*3 per cent. One bladder- worm subject occurs in about seventy- 
 six examinations, a ratio which is more than double that similarly 
 computed for T. solium (p. 531). It is, however, open to question 
 whether we can directly compare these two cases, and conclude that 
 Cysticercus cellulosce is twice as frequent as T. solium. For the results 
 of these examinations do not give one any correct impression as to 
 the numerical frequency of parasites, especially as regards those 
 which occur incidentally, and do not directly call for medical assist- 
 ance. In numerous cases of Cysticercus the trouble is a very serious 
 one, sometimes occasioning death ; but, besides these, there are a 
 
 1 Loc cit., p. 426. 2 loccit., p. 64. 3 See Vol. II. 
 
 4 " Statistik der menschlichen Entozoen." Dissert, inaug., Erlangen, 1874. 
 6 " Zur Statistik des Cysticercus cellulosae." Dissert, inaug., Berlin, 1877. 
 
542 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 great number of more trivial cases which never call for clinical 
 treatment. 
 
 The highest ratio furnished by our existing data is that of Berlin, 
 where the Cysticercus during the years 1866-1875 occurred, according 
 to Dressel, not less than eighty-seven times in 5300 dissections that 
 is, 1'6 per cent. In 1866 Virchow estimated this per-centage at two, 1 
 and with this agrees Rudolphi's report that in the anatomical threatre 
 at Berlin the Cysticercm only occurred four or five times in about 
 250 bodies. In Dresden the state of the case is very similar. Between 
 1852 and 1862 twenty- two cases of bladder- worm occurred out of 
 2002 examinations, that is, T9 per cent. ; while in the Pathological 
 Institute at Erlangen fourteen cases occurred among 1812 bodies, i.e., 
 0'78 per cent. (Miiller). In Gottingen the per-centage was 0*63, or 
 four out of 639. In Wiirzburg during seven years Virchow only saw 
 Cysticerci on very rare occasions, while the famous helminthologist 
 Bremser in Vienna had never seen one at all. The occurrence of this 
 parasite was first established there in the course of pathological 
 investigations, 2 but the cases were so few that they cannot at all be 
 compared with those occurring in Berlin, and in other districts of 
 North Germany. 3 
 
 The age and sex of the bladder-worm patients have been recorded 
 only by Dressel. From his report we first note the fact that the 
 majority of patients (thirty-nine out of the seventy-four whose age 
 was noted) were in the prime of life a result which also holds good 
 in regard to the adult Tcenia. Six of them were above seventy, one was 
 eighty- four years of age. In children the Cysticercus was only twice 
 found, once in a child three years old, and again in one " who seemed 
 to be only a few days " old. 
 
 The bladder-worms in adults were often calcified, so that one was 
 perhaps justified in referring them to an introduction in earlier years, 
 but, on the other hand, there were also some instances of fresh 
 Cysticerci. The latter prove at least this much, that the introduction 
 and development of the tape-worm brood is in the case of man in no- 
 way restricted to a definite age, as it seems to be, according to Gerlach, 
 
 1 V. Graefe, Archivf. Ophthalmology, Bd. xii., p. 2. 
 
 a Rokitansky, "Pathol. Anat.," Bd. ii., div. loc. 
 
 3 In agreement with this is the fact that Hebra observed among 10,000 patients 
 suffering from diseases of the skin only one case of bladder-worms in the subcutaneous 
 tissue, and that the Viennese oculists sought vainly for bladder- worms in the eye, while 
 those in Berlin noticed hundreds. Mauthner reports that in 30,000 eye-patients he had 
 never seen a Cysticercus. Berlin, in Stuttgart, found one among 40,000 patients, and 
 Wecker, in Paris, one in 60,000 ; while v. Graefe, in Berlin, estimates its occurrence at one 
 per thousand, and A. Grafe and Hirschberg at a still greater per-centage. (See Graefe 
 and Saemisch, " Handb. d. ges. Augenheilk.," Bd. iv., v., vL, loc. div.). Bladder- worms 
 in the eye are rare in Switzerland and in England. 
 
INFLUENCE OF AGE AND SEX. 543 
 
 in the case of the pig (p. 495). If the same conditions held good in 
 regard to man, then the maximum occurrence would be reached at the 
 end of childhood and not after maturity. 
 
 Especially striking and surprising is the above-mentioned case of 
 Cysticercus in a child " some days old." It is so well worth attention, 
 that one cannot but lament the brevity with which it is mentioned. 
 Since the bladder-worms are hardly recognisable as such "some days" 
 after their introduction, but require, as we have seen, two months for 
 their development, the infection must surely have taken place during 
 foetal life. 1 It is possible that the mother was infected, and that 
 from this source the foetus was penetrated by the wandering brood. 
 The six-hooked embryos might easily pass in some way or other (by 
 the blood-vessels ?) to the young, and would there gradually become 
 Cysticerci either in the muscles or in other organs. 
 
 The process which we here suppose is not perfectly isolated, since 
 we know of other Helminths, which, during their internal wanderings, 
 pass from the maternal body into the embryo (p. 67, note) ; but after 
 all the entirely negative results which we have in this connection in 
 regard to Trichina,* we were but little prepared to find this pheno- 
 menon exhibited in the case of Cysticerci. 
 
 It is a surprising fact that the majority of patients suffering from 
 bladder-worms are males, while T. solium is much more frequent in 
 women. There is no doubt as to the fact, which is evidenced not 
 only by Dressel's tables, but also by Kuchenmeister's reports on 
 Cysticerci 3 in the brain, and by the observations of v. Graefe on the 
 occurrence of bladder-worms in the eye. 4 Of the 87 cases noted by 
 Dressel,53 were males (2*4 per cent.) and only 34 females (1*6 per cent.). 
 Kiichenmeister found that among men Cysticerci in the brain were 
 almost half as numerous again as among women, while v. Graefe 
 reports that almost two-thirds of the 80 cases of bladder- worm in 
 the eye belonged to the male sex. 
 
 This constant preponderance of the male sex shows, of course, 
 that infection with embryos of Tcenia is favoured by the habits and 
 customs of men. It may be suggested at least that women are more 
 orderly and on the whole more cleanly than men. 
 
 1 We do not know the meaning of "some days," but it is possible that the infection 
 took place during birth ; that the child in passing through the vagina might, along with 
 the secretion, swallow some proglottides or eggs issuing from a Tcenia living in the in- 
 testine of the mother. The eggs have, according to Lewin, been found by Hausmann in 
 the mouth of the child. 
 
 2 See Vol. II. 
 
 " Ueber die Cysticercen des Hirns und ihr Verhaltniss zu Lahmungen, Epilepsie 
 und Geisteskrankheiten," Oestcrr. Zeitsckr. f. pract. Hcilk., 1868. 
 
 * " Bemerkungen uber Cysticercus," Archivf. Ophthalmdogie, loc. cit. 
 
544 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 The above fact leads us to the question By what ways and means 
 does man become infected by these embryos ? Of course an infection 
 of some sort must precede the appearance of Cysticerci. The days in 
 which one believed in a direct transmission of bladder-worms from 
 " measly " flesh are so long past, that it seems incredible when we 
 read, e.g., that even in 1851 Kiichenmeister regarded not only those 
 who reared and killed swine, &c., but also those working with raw 
 leather and skin, as peculiarly liable to bladder- worm disease. 1 
 
 The most direct and most frequent source of infection is, of 
 course, in the eggs, which are dispersed round about the abode of the 
 tape-worm, and are also widely distributed in the open air with the 
 excrement. Invisible to the naked eye, they may easily pass more 
 or less directly into man. Sometimes in drinking water or in vege- 
 tarian diet, sometimes in food into which the embryos have acci- 
 dentally found their way, or by the hand, to which they have adhered. 
 A dirty, untidy, crowded house increases the risk of infection enor- 
 mously, and hence the frequency of the disease is (according to Stein) 
 much greater among the lower classes. 
 
 "Where the infection is due to isolated eggs, the resulting bladder- 
 worms occur either singly or in small numbers. But this is not 
 always the case. On the whole, the numbers found in man are much 
 smaller than in the pig. And lately the results of v. Graefe and 
 Dressel have shown that cases of solitary occurrence are very fre- 
 quent. 2 But there are also cases known in which the bladder-worms 
 were as numerous as in the abundantly infected swine. Thus Stich 
 dissected a woman, a turf carrier, in whose muscles and subcutane- 
 ous tissue between 400 and 500 bladder-worms at least could be 
 counted. Lanceraux reports also the case of a rag-picker, 3 whose 
 muscles, especially in the thorax, were so abundantly penetrated by 
 bladder-worms, that their number was estimated at over 1000. 
 Similarly Lessing* reports the presence of more than 1000 Cysticerci 
 in the body of an insane patient. In Bonhomme 5 we read of a 
 patient seventy-seven years old, who, besides 900 bladder-worms in 
 the muscles, bore also upwards of 2000 in the subcutaneous tissue, 
 besides numerous specimens in the brain and lungs. A policeman, 
 thirty -two years old, who died with severe symptoms of cerebral 
 disease, exhibited on dissection numerous Cysticerci in the brain, and 
 also a great number of muscle bladder-worms, especially in the ex- 
 
 1 Archivf. pathol. Anat., Bd. iv., p. 65, 1851. 
 
 * Dressel's reports yield the surprising result that in almost 37 per cent, there was 
 but one Cysticercus. 
 
 3 Archiv. ginir. mtd., t. xx., p. 545, 1872. 
 
 4 Schmidt's Jahrbiicher, Bd. xcix., p. 98, 1858. 
 
 6 Comptes rendus soc. bid., t. v., p. 62, 1864, or Archiv. gtntr. mtd., t. i., p. 355, 1865. 
 
INFECTION BY WHOLE PROGLOTTIDES. 545 
 
 tremities, which seemed almost "stuffed" with them. 1 Similarly 
 Gubain reports 2 a case where the muscles and internal organs (heart, 
 brain, and viscera) were so full of bladder-worms " that had one not 
 seen the resulting disorganization one would not have believed it." 
 
 Such occurrences cannot, of course, be referred to the introduction 
 of isolated eggs ; it must have taken place en masse, either by a large 
 number of newly expelled eggs, 3 or of eggs still within the proglottis. 
 In other words, whole proglottides or series of them may be trans- 
 ferred to the stomach of their host, and there liberate the eggs. 
 
 We can hardly bring ourselves to suppose that it can ever happen 
 that man should infect himself with a whole brood as the swine do. 
 One must, however, face the facts, apart from any aesthetic prejudice, 
 and there are several disgusting possibilities of this sort. 
 
 First, we must remember that there are among men coprophagous 
 persons even besides the insane, and such an one may easily become 
 infected like a pig. 4 The only question is as to the real existence of 
 such a habit. On this point we have suspicion rather than fact to go 
 upon. But at any rate this does not exhaust the possibilities of in- 
 fection en masse, for the proglottides may also by themselves find their 
 way to the mouth. 
 
 We cannot suppose that any one would wittingly swallow a tape- 
 worm joint. But apart from the possibilities open to children and 
 the insane, the tape-worm patient may readily infect himself with 
 the proglottides during sleep by lifting the hand to the mouth. The 
 transference is, however, more frequent when, by shrivelling and 
 drying up, the proglottides become indistinguishable, are then car- 
 ried by chance in various directions, which distribution sometimes 
 not unnaturally results in their being swallowed. Disorder and un- 
 cleanliness in the room and house are fertile sources of increased risk. 
 
 When an inmate of the house or a member of the family suffers 
 from Tcenia solium, there is obviously special necessity for cleanli- 
 ness and care. The linen of the patient should be frequently changed, 
 the buttocks and hands should be frequently washed, the excrement 
 carefully removed, and the voided proglottides destroyed, if possible, 
 by burning, without touching the hands. The patient is himself in 
 greatest danger of self-infection. 
 
 1 Onymus, Gaz. des hop., p. 237, 1865. 
 
 - Quoted by Stich, loc. cit. t p. 176. 
 
 n We may also note that even after an abundant introduction, only one bladder- worm, 
 or but a few, may develop. 
 
 4 In fact Wendt and Birch-Hirschfeld have found numerous Cysticerci in the brain of 
 a coprophagous tape- worm patient. Wendt, Allgem. Zeitschr. f. Psychiatrie, Bd. iii., 
 1872 ; and Birch-Hirschfeld, Jahrb. d. pathol Anat., p. 203, 1876. 
 
 2 M 
 
546 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 This latter does, indeed, occur very abundantly among bladder- 
 worm patients. Kiichenmeister is even of the opinion that the above- 
 mentioned preponderance of male patients is due to greater possibility 
 of self-infection. In support of his position he refers 1 to the male 
 clothing, which makes the removal of spontaneously liberated pro- 
 glottides difficult, and also to outdoor work, which frequently compels 
 a man to ease himself in the open air under circumstances which make 
 defiling of the hands very easy. 
 
 On the other hand, there are investigators, and among them such 
 a prominent scholar as Virchow, who would refer but few cases to 
 self-infection, and are even inclined to question its existence. They 
 refer to the results of statistics, according to which the occurrence of 
 a Tcenia solium has been but seldom proved in a bladder- worm 
 patient, so that the cases of their associated occurrence are probably 
 accidental, and do not admit of any conclusion being drawn as to the 
 origin of the Cysticerd. 
 
 Graefe is their chief witness, who, 2 out of eighty cases of Cysti- 
 cercus, found only five or six in which he could prove the presence of 
 a Tcenia, while in a great number of cases the persons who shared the 
 same room with the patient suffered from tape-worm. Dressel's 
 testimony is still more emphatic ; for in the cases compiled by him 
 from clinical reports, there was not one of a tape -worm and bladder- 
 worm co-existent, though he acknowledges that, not knowing the 
 history of the patients in question, he could not say that the patients 
 had not formerly suffered from tape-worm. But this last question is 
 a most decisive one ; for while the bladder-worms persist after they 
 have once been developed, the tape-worm often lives for a com- 
 paratively short time in the intestine of its host. 
 
 For this reason we may assume that cases of co-existence of tape- 
 worm and bladder-worm represent but a small fraction of those cases 
 in which the bladder- worm hosts have been also tape- worm hosts. 
 The twenty to twenty-one cases of such co-existence, which Lewin a 
 has earned our thanks by collecting from the scattered and hardly 
 accessible reports, are by no means of such little weight as one might 
 at first sight suppose. And this, too, must be remembered, that they 
 all refer to recent decades, at a time when the relations between 
 
 1 Loc. cit., second edition, p, 108. a Loc. cit. 
 
 3 Loc. cit., p. 651. Kuchenmeister erroneously reports the number only at eleven. 
 Two other cases have been since discovered by Miiller, a third by Heller (Ziemssen's 
 44 Handbuch," Bd. iii., p. 331 ; Eng. transl., p. 599), and a fourth by v. Wecker (v. Graefe 
 u. Samisch, 44 Handbuch d. ges. Augenheilkunde," Bd. iv., p. 713). Boyron ("Etude 
 sur la ladrerie chez rhomme," Paris, 1876) also reports cases of two bladder-worm patients 
 also infected with tape- worm (Observ. i. and iv.), so that the total number of cases is about 
 twenty-seven. 
 
DIRECT TRANSFERENCE FROM THE INTESTINE TO THE STOMACH. 547 
 
 Cysticercus cellulosce and Twnia solium were as yet unapprehended, 
 and when the presence of tape-worm in cases of bladder-worm might 
 attract no special attention. 
 
 It is, however, by no means necessary that the transmission of a 
 brood should take place through the mouth. The eggs are, indeed, in 
 all cases subject to the action of the gastric juice (p. 153), but a trans- 
 ference from the intestine into the stomach may take place directly 
 when the contents of the former are driven forwards by antiperistaltic 
 contraction. Sometimes it is but single proglottides which pass back 
 in this way, sometimes longer stretches of joints, so that an infection 
 may thus be brought about, resulting in an abundant occurrence of 
 Cystic&rci. Such being the case, it is quite possible that one or other 
 of the above-mentioned cases was due to a self-infection of this sort. 
 
 The fact that there are numerous cases of tape- worms (Tcenia 
 solium of course) where the host never becomes infected by bladder- 
 worms, cannot, of course, be used as an argument against the 
 assumption of this " entocoelic " self-infection. It could be used as 
 such only if the digestion of the egg membranes and the liberation of 
 the embryos were possible while the eggs were still in the intestine. 
 This is, indeed, alleged by Kiichenmeister, 1 and more recently by 
 Klebs 3 and Lewin. In this case, the existence of a tape-worm host 
 without bladder-worms would be exceptional, while we know that 
 exactly the reverse is true. 
 
 In rare cases the* transference of proglottides into the stomach 
 may be facilitated by the abnormal position of the tape-worm. Some- 
 times one finds the worm hanging upwards 3 in the intestine, so that 
 the proglottides are approximated to the stomach. It is doubtful, 
 however, whether this position was permanent. At any rate, one must 
 remember that the position of the tape-worm in the intestine is de- 
 termined by extraneous forces (pressure of the chyme, contraction of 
 the intestine, &c.), as well as by the motions of the worm itself. 
 
 The proglottides passing into the stomach from the intestine 
 can cause infection only when they remain some considerable time 
 in the former. When they merely pass into the stomach to be 
 
 1 " Parasiten," first edition, p. 12. Kiichenineister maintains that the embryos may be 
 liberated, and may develop even in the oesophagus. Only after I published my objections 
 (" Blasenbandwiirmer," p. 102), and proved experimentally that the embryos could only be 
 liberated by the action of the gastric juice (" Parasiten," first edition, p. 116), did he change 
 his opinion. That did not, however, hinder him from asserting in pp. 98 and 115 of the 
 new edition that he was the first to show that a transference into the stomach was neces- 
 sary for the liberation of the embryos. We do not need now-a-days seriously to contra- 
 dicr or disprove the statement of Kiichenmeister, that the bladder- worms found in the 
 peripheral regions, such as the conjunctiva, arise from direct immigration from outside. 
 
 2 "Handbuch d. pathol. Anat.," p. 301, 1868. 
 
 8 A case of this sort (by Siebert) is found in da Contn, loc. cit., p 162. 
 
548 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 expelled by the mouth, the action of the digestive juices has not time 
 to liberate the embryos. Thus we understand that among the cases 
 enumerated by Lewin, 1 in which larger or smaller pieces of Tcenia, 
 solium were voided, there are only two instances (those of Kuntz- 
 mann and Witthauer) in which bladder-worm disease has been 
 certainly established. On the other hand, Dressel cites a case in 
 which a tape-worm (it is not expressly said that it was T. solium) was 
 found in the duodenum and stomach, " in a place which could hardly 
 have been more favourable for self-infection," but yet none took place. 
 It is impossible to prove, however, that the worm occupied this un- 
 usual position during the life of the host, and did not assume it on 
 the approach of death. 
 
 But, granted that the infection has taken place in some way or 
 other, then the embryos distribute themselves in the body according 
 to circumstances, and become bladder-worms. How they wander we 
 cannot say with certainty. At any rate, they may reach any part or 
 organ of the body, except, perhaps, the bones, 2 which are probably 
 protected more by their being ill-suited for development than by their 
 inaccessibility. The bladder-worms are found, strangely enough, but 
 rarely in the liver a contrast to the Echi'twcoccus. 
 
 From the analogy of its occurrence in swine, we are led to the 
 conclusion that it is the muscles, or rather the intra-muscular connec- 
 tive-tissue, which the bladder- worms most frequently inhabit. The 
 results of dissections seemed in harmony with this till our attention 
 was lately directed, especially by Dressel's reports, to the extraordi- 
 nary frequency with which this worm occurs in the brain. Whether 
 this result of pathological examination is a true expression of the real 
 state of the case is, however, doubtful, since bladder- worms in the 
 muscles are apt to escape the notice of pathological anatomists and of 
 clinical surgeons, while the cases of bladder-worms in the brain as 
 naturally demand their attention. The deceptiveness of statistics 
 obtained from purely pathological examinations is most strikingly 
 shown by the fact that Dressel notes in his eighty-seven cases only 
 three instances of bladder-worms in the skin, while Lewin observed 
 as many within a single year. The frequency of the bladder- worms 
 in the eye has been demonstrated by means of the ophthalmoscope ; 
 but before this instrument was used they were held as great rarities. 
 In pathological anatomical institutes they are even yet so rare that 
 neither Mliller nor Dressel mentions them. The thirty-six cases of 
 the former refer for the most part only to the brain (twenty-one), the 
 
 1 Loc. '<., p. 658. 
 
 2 It is doubtful whether the case in Froriep's " Chirurg. Kupfertafeln " (438) is 
 established or not. 
 
FREQUENCY OF OCCURRENCE IN THE VARIOUS ORGANS. 549 
 
 muscles (twelve), and the heart (three) ; and the reports are so 
 unequally divided between Dresden and Erlangen that, e.g., out of 
 twenty-two cases, eleven cases of Cysticerci in the muscles are recorded 
 in the former, while, out of fourteen cases in Erlangen, only a single 
 one is reported. 
 
 According to Dressel's lists, among the eighty-seven cases of 
 bladder-worms at Berlin, seventy-two were in the brain, thirteen in 
 the muscles, and six in the heart. There were, besides, three cases of 
 Cysticerci in the lungs, three in the subcutaneous tissue, and two in 
 the liver. These cases enumerated exceed the total eighty-seven ; but 
 this results from the fact that the bladder- worms are by no means 
 always restricted to a single organ. This is generally the case, how- 
 ever, when they were found in the brain or eye; for, among the 
 seventy-two cases of cerebral bladder-worms, there were no fewer 
 than sixty-six in which the parasites were restricted to these organs. 
 Similarly Graefe reports that in the eighty cases of bladder- worms in 
 the eye observed by him up to 1866, there were no patients in whom 
 he could demonstrate their presence elsewhere, except two, who 
 possibly harboured them in the brain. 1 When the bladder-worms 
 occur in other organs, then the local limitation seems to be less fre- 
 quent, as may be inferred from the fact that in Dressel's cases there 
 were but four in which the bladder- worms occurred only in the 
 muscles, and only two in which they were confined to the heart. 
 
 The Cysticerci in the brain are usually found in the membranes 
 and in the cortex. The Sylvian fissure is specially frequented, as are 
 also the large ganglia, the corpora striata, and the optic thalami. 
 The fourth ventricle occasionally contains them, as also the choroid 
 plexus. On the contrary, bladder- worms have been found only four 
 times in the substance of the cerebrum and cerebellum. 2 They 
 occurred still more rarely at the base of the brain. On the frontal 
 lobes they were found four times, on the lower surface of the pons 
 once, and also once between the two optic nerves. As to the Cysticerci 
 in the muscles, no favourite place could be inferred from Dressel's cases, 
 although it certainly seemed as though the pectoral muscles are very 
 frequently diseased. But there was hardly a group of muscles which 
 was avoided by the bladder- worms ; the muscles of the extremities were 
 as much infected as the intercostals, or those of the abdomen and the 
 
 1 Dr. R. Schulz of Brunswick told me of a case of Cysticercus in the retina which 
 occurred along with many in the subcutaneous tissue. 
 
 2 This maybe inferred from Kiichenmeister's report (Oesterr. Zeitschr. f. pract. ffeilk., 
 1866). In the eighty-eight cases here collected the bladder-worms were found forty-nine 
 times in the membranes, thirty-nine times on the surface of the hemispheres, thirty-six 
 times in the great ganglia, but only nineteen times in the central substance, and eighteen 
 times in the ventricles. 
 
550 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 psoas. The musculature of the ventricles and auricles was frequented, 
 as was also the inner layer of the pericardium and endocardium. 
 Under the superficial membrane, the bladder-worms not unfrequently 
 form vesicular dilatations, and (especially in the endocardium) papillar 
 or stalked appendages ; and a Cysticercus has been observed even in 
 the walls of the blood-vessels. 
 
 Of special interest is the occurrence of Cysticerci in the eye, partly 
 because it is common and soon makes itself perceptible, partly also 
 because it affords opportunity for observing the worm in its natural 
 environment, and of following out its development. We owe this to 
 the discovery and application of the ophthalmoscope, and the sensation 
 which its revelations excited was all the greater since previous experi- 
 ence of bladder-worms in the eye had been limited to but few cases. l 
 
 Von Graefe, to whom we owe our first account of these surprising 
 discoveries, calculates, on the strength of a very large mass of statistics, 2 
 that the occurrence of the Cysticercus in the deeper parts of the eye at 
 about one per thousand among the patients at the Berlin Ophthalmic 
 Institute. In the anterior parts of the eye he only reports nine 
 cases (five in the conjunctiva, two in the anterior chamber, one in the 
 lens, and only one in the orbit) ; but these represent hardly the eighth 
 part of those found in the vitreous humour, or in the subretinal 
 tissue. Those in the latter situation are by far the most frequent, 
 standing to those found in the vitreous humour in the ratio of 2 : 1. 
 
 In the cases mentioned by v. Graefe it was always only a single 
 Cysticercus which inhabited the eye ; and so also with others, with 
 the exception of a single case observed by 0. Becker, where one 
 Cysticercus occurred in the vitreous humour and another in the 
 retina. This solitary mode of occurrence is peculiar to man, for in 
 the pig the eye occasionally contains a considerable number. Xord- 
 inann counted in one case twelve, of which six were in the vitreous 
 humour, and the other six between the sclerotic and the choroid. 3 
 
 In the chambers of the eye the Cysticercus is almost always 
 free i.e., without a capsule, and swimming in the fluid ; so that its 
 position may vary with the attitude of the head and the direction of 
 the eyes, as well as with its own movements, which consist partly of 
 an undulating peristalsis of the bladder, but principally of an alternate 
 protrusion and retraction of the head. At the point of insertion of 
 
 1 The first observation on the occurrence of a bladder-worm in the eye (the anterior 
 chamber) is furnished by Schott and Sommering. Oken's Isis, p. 717, 1830. 
 
 2 From the Verkandl. Berlin. Med. Geaellsch., 1867-68, p. 96, 1871, I extract the 
 statement that v. Graefe has observed over 100 cases of bladder-worms in the eye. The 
 observations in the text rest on v. Graefe's notes on Cysticercus (Archiv f. ophthalmdoyie, 
 Bd. xii, p. 174). 
 
 8 Mikrographische Beitrage, Th. i., p. 13 : Berlin, 1832. 
 
EFFECTS OF BLADDER-WORMS IN THE EYE. 551 
 
 the process one observes a blunt, proboscis-like projection. 1 In the 
 interior of this the quadrangular head may be recognised, which is 
 usually soon extruded, so that the whole appendage, with narrow 
 neck and wrinkled body, is free down to the constricted base. Gene- 
 rally the movement of the rostellum and suckers is to be seen ; they 
 are protruded in varying fashion, the head rotates on the neck, and 
 the whole appendage exhibits a periodic retraction, so that it some- 
 times approaches the bladder, and at other times projects directly 
 from it. At certain times the movements are almost continuous, 
 while at other times the appendage hangs out almost immoveably 
 from the bladder, so that one might readily suppose the worm to be 
 dead. 2 The movements of the worm are usually excited by the 
 contraction of the iris; by the use of atropine there is a marked 
 diminution, but whether by direct or indirect operation is uncertain. 
 The diamond-like glitter which one sometimes sees when the rostellum 
 is protruded depends probably on the hooks, which change their 
 position somewhat in consequence of the movement. Similarly, the 
 point-like excrescences on the bladder can hardly be anything but 
 the above -described microscopic projections characteristic of the 
 Cysticercus cellulosce. 
 
 As in the aqueous, so it is in the vitreous humour, only of course 
 with this difference, that the movements are more and more restricted 
 by the threads and membranous thickenings which gradually develop. 
 In many cases a sort of capsule is formed round the worm. 
 
 In the first edition of this work I have already expressed the 
 supposition, 3 which has been reiterated by my old friend v. Zehender, 
 that the bladder-worms of the chambers of the eye and of the vitreous 
 humour were not developed there, but were first embedded in the adja- 
 cent membranes iris or choroid and that they subsequently became 
 free, just as I have proved in regard to the bladder- worms of the body- 
 cavity (C. pisiformis and C. tenuicollis), which, after their passage from 
 the liver, remain fur a while free before they are ultimately sur- 
 rounded by a cyst. 
 
 On closer scrutiny of the ophthalmological literature on this 
 point, and especially of the account which v. Wecker and Leber have 
 given in the well-known text-book on general ophthalmology by v. 
 
 1 See von Wecker in " Handbuch d. ges. Augenheilk.," by von Graefe and Samisch, 
 Bd. iv., p. 708. 
 
 2 See the observations of Sommering (loc. cit. ), and of Mackenzie, Med. - Chirurg. 
 Trans., vol. xxxii., 1849. 
 
 3 Kiichenmeister expresses the same supposition in the second edition of his work on 
 parasites (p. 250), and imagines that he renders his own opinions of greater weight by calling 
 mine " an anatomical presentiment." 
 
552 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 Graefe and Samisch on the diseases of the vitreous humour 1 and 
 retina, 2 I am convinced that my opinion was perfectly justified. 
 What is here given us is little less than a complete history of the 
 bladder-worms inhabiting the vitreous humour, and an adequate de- 
 monstration is given of the fact that these worms originate in the 
 subretinal membranes. 
 
 In ophthalmoscopic examination the bladder-worm appears first 
 as a bluish-white, sharply defined body, and lies behind the retina, 
 so that the vessels of the latter extend over it. The bladder is easily 
 flattened by pressure, and exhibits the head as a clear spot shining 
 through. The latter is always invaginated, and never protrudes, 
 although the wall of the bladder constricts and dilates in an un- 
 dulating fashion. In many cases the worm moves away from its 
 original seat, loosening and disturbing the retina over an increasing 
 area. The vitreous humour is also penetrated by delicate membranous 
 opacities, which extend in front of the bladder like a veil or curtain, 
 with dark folds and stripes. Subsequently the retina is partially 
 destroyed by the increasing pressure of the bladder, so that the latter 
 falls forward into the vitreous humour. Sometimes one sees how the 
 neck with the head is protruded through the opening. When the 
 whole worm has broken through into the vitreous humour, its former 
 seat may still be seen as a discoloured spot of irregular form, while 
 the point of rupture can be but rarely seen with any distinctness, 
 owing to the turbidity of the vitreous humour. 
 
 If frequent change of position, or copious discharge of fluid under 
 the retina, have led to an extensive or total loosening of the same, the 
 Cysticercus remains lying where it was, and does not break through 
 
 into the vitreous humour. The bladder then 
 becomes encapsuled by connective tissue, 
 which gradually acquires a firmer nature, 
 and may finally undergo a partial ossification. 
 On sections of such eyes the bladder 
 is seen lying between the choroid and the 
 retina. Round about the worm, or over 
 the whole extent, the retina is much thick- 
 ened by proliferated connective tissue, and 
 has fused with the capsule, or is sometimes 
 
 FIG. 298. Subretinal Cysti- . L ' ... 
 
 cercus in the eye, after v.Wecker atrophied. Similarly the choroid IS SOme- 
 
 (nat. size). times also involved in the exuberant growth 
 
 of connective tissue. 
 
 Less frequently there is formed round the parasite, at an early 
 stage, an envelope of delicate vascular connective tissue, which raises 
 1 Bd. iv., p. 709. 2 Bd. v., p. 708. 
 
EFFECTS PRODUCED IN ANTERIOR AND POSTERIOR CHAMBERS. 553 
 
 the still transparent retina like a tumour, but is sometimes deserted by 
 its inmate, which then settles at another place, and is encapsuled anew. 
 
 The observations here related do not exclude the possibility that, 
 besides the bladder-worms which subsequently pass into the vitreous 
 humour, there are also some which have developed there from the 
 first. But while no positive argument can be given in favour of 
 this idea, on the other hand, all we know of the development of 
 Cysticercus leads to the supposition that the first stages must always 
 be spent in a vascular tissue. We are, however, justified in believing 
 that the exit of the bladder-worm from the surrounding tissue might 
 sometimes take place at an earlier stage of development, at a time 
 when the changes in the retina had not yet attained their subsequent 
 extent, and were therefore less noticeable. But the incipient stages 
 of the Cysticercoid disease in the eye have as yet eluded investi- 
 gation. 1 
 
 In the bladder- worms inhabiting the anterior chamber of the eye, 
 an early exit is perhaps more frequent than among those infesting the 
 vitreous humour, as one could, indeed, infer from the fact that the 
 aqueous humour presents much less resistance to the growing bladder- 
 worm. Indeed, the Cysticerci are usually found free in the aqueous 
 humour. Yet there are cases which demonstrate a connection be- 
 tween these free forms and the iris ; an actual union has, indeed, been 
 repeatedly observed. 2 Thus Dalrymple observed a case where the 
 bladder was so fastened to the iris that the latter looked as though 
 perforated by it. In another case (recorded by 
 Teale), the worm connected by its cyst with the 
 iris was hardly bigger than a hemp-seed, and from 
 the shortness of the neck might be seen to be quite 
 a young Cysticercus. The case lately described by 
 Kuchenmeister 3 ought also to be noted ; for here, 
 besides the free Cysticercus in the anterior chamber, 
 there was also a connective tissue cyst adherent to 
 the posterior wall of the iris, which latter was FI G- 299. Bladder- 
 reasonably regarded as its bladder. Since it con- Camber* ^tb?^? 
 tained only a clear fluid, it must have closed up after v.Wecker. (x3.) 
 after the exit of its inmate and become filled with serum. 
 
 The bladder-worms of the interior of the eye are not the only ones 
 found free within serous cavities. In the ventricles of the brain they 
 
 1 The smallest bladder-worms seen by v. Graefe measured 3 to 4 mm. In three or 
 four weeks after the appearance of the first, he noticed, with the ophthalmoscope, marked 
 changes. Some weeks later, the worms had a diameter of 5 to 6 mm., and after two years 
 they had increased to 11 mm. Archiv f. Ophthalmologie, Bd. xii., 2, p. 188. 
 
 2 See v. Wecker, " Handbuch d. ges. Augenheilkunde, " Bd. iv., p. 575. 
 " Parasiten," second edition, p. 249. 
 
554 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 sometimes occur, usually without any envelope. We need not again 
 note that here also we have to do with a secondary condition. 1 The 
 worms in question obviously originate in the choroid plexus, which is 
 sometimes, as we have seen, inhabited by bladder-worms. 
 
 The same may be said of the bladder-worms which are found in 
 the meshes of the arachnoid and pia mater on the surface of the 
 brain. They have usually an irregular form, and sometimes vary so 
 much from the ordinary type that their true nature is not evident at 
 the first glance. These extreme cases are called " branched " Cysticerci 
 (C. racemosus) by Zenker, who lately directed our attention to them. 2 
 The name is not inapt, since they often appear as long extended 
 cylindrical bodies (sometimes 8, or even, according to Heller, 25 cm. 
 long), of varying thickness, and giving off in their course numerous 
 more or less large bladders. The latter are not unfrequently stalked, 
 and are beset with irregular daughter-bladders, so that their ap- 
 pearance varies greatly. Heads are but seldom found, and at 
 
 most only one to each bunch. They 
 have the characters of Tcenia solium, 
 and show their connection with it by 
 sometimes occurring along with the 
 genuine Cysticercus cellulosce (as in 
 Marchand's case), and by the latter 
 being connected with them by inter- 
 Fio .300 .-Cysticercus racemosus, mediate stages. 8 Besides, they have 
 
 after Marchand (nat. size). 
 
 also the microscopic protuberances of 
 
 the cuticle, and the scattered calcareous bodies like the common 
 Cysticercus cellulosce. 
 
 We do not yet know by what circumstances this unusual growth 
 is determined, but we may conjecture that the form of the enclosing 
 space and the course of the blood-vessels which penetrate the mem- 
 branes of the brain and pass out on to the surface, have something to 
 do with it. This fact also ought to be noted, that, according to Mar- 
 chand, the attached bladders do not merely arise by protrusion of the 
 wall of the bladder, but result in part from buds which are formed on 
 
 1 In the case observed by Zenker, in which a Cysticercus was found free in an 
 aneurisinal sac attached to the vertebral artery (Heller, in " Ziemssen's Handbuch," Bd. 
 iii., p. 344 ; Eng. transl., p. 609), I think this sac should be regarded as the bladder which 
 ultimately came into communication with the lumen of the vessel 
 
 2 See Heller, loc. cit., p. 823 ; Eng. transl., p. 598. Also, Marchand, " Ein Fall von 
 sog. Cysticercus racemosus des Gehirnes," Archiv f. pathvl. Anat., Bd. Ixxv., p. 104, 
 1879. I must also note that the irregular form of the Cysticerci in the brain was pre- 
 viously known to Helminthologists. 
 
 3 In one of Zenker's cases the patient had also suffered from Tcenia solium. Heller, 
 loc. cit., p. 334 ; Eng. transl., p. 599. 
 
VARIATIONS IN FORM AND SIZE OF THE BLADDER. 555 
 
 the wall like the daughter-bladders of Echinococcus. According to 
 Heller, these bodies extend with the arachnoid, sometimes into the 
 third ventricle and into the lateral ventricles, and always retain the 
 same racemose appearance. 
 
 We cannot doubt that mechanical forces, and especially pressure, 
 exert a determining influence on the shape of the bladder-worms. 
 This may be proved by the ellipsoidal shape of the muscular bladder- 
 worms, which gradually results, as we know, from the original 
 spherical form through the pressure exerted by the muscular fibres in 
 contracting. When such determining factors are absent, 1 and the 
 conditions of growth are the same on all sides, then the normal 
 spheroidal shape is retained. 
 
 As the shape of the bladder is determined by the mechanical 
 factors of the environment, so is its size determined by the nutritive 
 conditions. The results of my experimental rearing of bladder- worms 
 proved that Cysticerd of equal age were not of equal size in different 
 parts of the body. Even in the same organ there are sometimes 
 larger and smaller bladder- worms side by side, and yet we cannot dis- 
 tinguish them either in age or in phase of development. The size is 
 on an average about that of a pea or small bean, but it is very vari- 
 able. The larger forms are generally found in the internal organs, 
 in situations especially where their growth is but little hindered, as 
 on the free surface of the viscera (liver and heart) and of the brain. 
 In the ventricles of the brain the Cysticercus cellulosce sometimes 
 grows to the size of a pigeon's egg. In the eye, on the other hand, 
 and especially in the chambers of the eye, the worm generally remains 
 small and stunted. 
 
 After the death of the worm, a marked decrease in size at once 
 sets in. The bladder fluid is absorbed, the bladder itself collapses, 
 and the surrounding cyst, unless endowed with unusual power of 
 resistance, undergoes similar changes. In the muscles it assumes the 
 form of a long strip, hardly 2 mm. broad, lying between the fibres, 
 and has a tendinous appearance (Stich). Some traces of the former 
 parasites always persist, even though they be only the remains of the 
 capsule or its calcareous contents, by the action of acids upon which 
 a few hooks may sometimes be seen. 
 
 It is not, however, always or exclusively the form and size of the 
 bladder which vary thus in different cases. The head not unfre- 
 quently exhibits great differences. This is especially the case in the 
 larger bladder-worms from the brain, of which I saw specimens whose 
 
 1 Dressel once observed at the base of the brain an almond-shaped bladder-worm, 
 and rightly supposed that it owed its shape to the pressure exerted on it by the whole 
 mass of the brain. (Loc. cit., p. 17.) 
 
556 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 Lead-processes when protruded were 2 cm. and upwards in length. In 
 the retracted state, such a head-process is usually coiled in a regular 
 
 spiral of sometimes three turns. 
 Koberle', who first described 
 such forms, 1 thought he was 
 justified in erecting them into 
 a species distinct from Cysticer- 
 cus cellulosce in the form and 
 size of the hooks (Cyst, turbi- 
 natus). I have, however, con- 
 vinced myself by accurate com- 
 parison that there are no 
 specific differences between the 
 two forms. Probably the ex- 
 cessive length of the body 
 depends on the age attained by 
 
 FIG. 301. Bladder-worm from the brain with the bladder-worm in question 
 a spirally coiled body. ( x 12. ) ^ ^ ^ 
 
 Nor can I recognise the Cysticercus melanocephalus of the same 
 author, 2 a species established on the strength of a single form also 
 found in the brain. It seemed indeed to be distinguishable by certain 
 peculiarities in its hooks, but the reports of the author are by no means 
 convincing. As to the erection of a species on the strength of the 
 nature of the head-process, this has as little diagnostic value as the 
 presence of the black pigment which is more rarely seen in the 
 bladder-worms than in the adult Tcenice, but occurs sometimes even 
 in this stage. 
 
 The almost countless observations which have been made since. 
 Werner's days on the Cijsticercus cellulosce of man prove clearly how 
 much attention has been attracted to these structures by the discovery 
 of their animal nature. What was formerly known is so disproportion- 
 ately little, that it was for long a current opinion that Werner was 
 the first to find bladder-worms in man. The error of this is evident 
 from the fact that in the well-known compilation of Bonetus 8 I find* 
 a case observed by Wharton (1679), " de glandulis sanis varias corporis 
 partes occupantibus in milite," which obviously refers to bladder- worms 
 in the skin or muscles. One of these so-called "glands" was cut 
 out by a surgeon, and since it "citra ullum putridum aut con-up- 
 turn humorem tota ex solida glandulosa atque alba carne constabat," 
 
 1 Koberte, " Des Cysticerques de Tsenias de 1' homme," pp. 22, 29 : Paris, 1861. 
 
 2 Ibid., pp. 25, 30. 
 
 3 " Sepulchretum e. Anatomia practica," p. 1540 : Geneva, 1679. 
 
 4 " Blasenbandwurmer," p. 3. 
 
OLDER OBSERVATIONS UPON BLADDER-WORMS. 557 
 
 it appeared to him to furnish proof " dare glandulas adventitias plane 
 sanas, nisi quod in numero partium prsenaturalium recenseantur." 
 I formerly expressed the opinion that this case of bladder-worms in 
 man was " perhaps " the oldest known, but I have learned from 
 Klichenmeister 1 that in 1558 Eumler observed in the dura mater and 
 roof of the skull of an epileptic patient certain tumours in regard to 
 which the question arose " num pustulse illse morbi Gallic! soboles 
 fuerint." Similarly Panarolus in 1650 saw Cysticerci on the corpus 
 callosum of an epileptic priest. 2 But, including these cases, the old 
 reports as to bladder-worms are extraordinarily scanty. Nevertheless 
 it seems as though the structures in question had been very generally 
 known to physicians from that time onwards. This may be partly in- 
 ferred from the statement of Hartmann, the discoverer of the animal 
 nature of bladder-worms in general and of those of the pig in parti- 
 cular (p. 511), who in his last communication 3 speaks as follows: 
 " Glandia, aut quocunque nomine his affines veniant pustulne, nidos 
 esse vermiculorum, inihi fit veresimile." We need not note how strik- 
 ingly the supposition thus expressed has been fulfilled. 
 
 The importance of these worms from a clinical point of view was 
 probably first noticed in connection with those found in the brain. 
 Since these were found to be present in patients who had suffered 
 from cerebral or mental diseases, it was natural to connect the two, 
 and that all the more since it had been widely recognised 4 since 
 Wepfer's investigations in 1672 that the staggers of sheep and oxen 
 was due to a watery bladder found in the brain. The latter was 
 our Ccenurus, whose animal nature was first recognised in Goze's 
 time by Leske. 5 Before Werner's discovery, Goze, along with other 
 observers, such as Morgagni, called attention to the fact that certain 
 " extraordinary diseases of the head " were readily occasioned by Tcenice 
 vesicular es. 6 
 
 The pathological phenomena evoked by Cysticercus cellulosce are 
 very variable, according to the occurrence and position of the parasites. 
 Where they are found exclusively in the subcutaneous connective 
 tissue, or in the musculature of the body, they may be almost harmless. 
 
 1 "Parasiten," second edition, p. 58. Kiichenmeister seems to have overlooked the 
 " perhaps." 
 
 2 See for further particulars regarding this case, Kuchenmeister's studies on the his- 
 tory of Cestodes, Deutsches Archiv f. Gesckichte der Medicin, Bd. ii., Heft. 4. 
 
 3 Ephem. Acad. nat. cur., Dec. ii., Ann. vii., p. 58, 1688. 
 
 4 " De Apoplexia," p. 56. 
 
 ' ' Von dem Drehen der Schafe und dem Blasenbandwurm im Gehirn derselben als 
 Ursache dieser Krankheit : " Leipzig, 1788. 
 
 6 Loc. cit., p. 249. Among the cases here mentioned, those of Weikard may be 
 referred with tolerable certainty to Cysticercus celluloses. 
 
558 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 The worms inhabiting the cutis may be felt through the skin as 
 moveable tumours about the size of a pea, but cause hardly any 
 discomfort. They come and go almost unnoticed, unless it be that 
 owing to their position on the nates or on the back, or in some other 
 situation where they are exposed to considerable external pressure, 
 their capsular wall becomes inflamed, and results in the formation of 
 an abscess. 1 A spontaneous inflammation caused by the bladder- 
 worms alone is as yet unknown, though in a few cases the infected 
 muscular tissue has exhibited a somewhat reddened appearance. As 
 regards discharge of function, a decrease of muscular strength is the 
 most that has ever been observed. 
 
 Those cases, however, in which the bladder-worms inhabit the 
 heart seem more serious. But on superficial positions the worms seem 
 hardly capable of occasioning any marked disturbance; but it is 
 different when they lie under the endocardium, or are fixed as stalked 
 bladders to the valves. In such cases we find to a varying extent 
 symptoms of endocarditis, and such phenomena as valvular insuffi- 
 ciency and stenosis, besides palpitation, impeded respiration, and 
 syncope. Without further proof, such as of course primarily the 
 direct demonstration of bladder-worms under the skin or in the eye, 
 the true nature of these troubles could hardly be determined with any 
 certainty. This is true also of the visceral Cysticerci, which excite 
 symptoms that have hardly any special or distinctive pathological 
 character, and that vary according to the position of the worms. 
 In the respiratory organs they occasion asthma, and sometimes even 
 inflammatory conditions; in the walls of the intestine they cause 
 peritonitis, &c. 
 
 The disturbances of functions and the pathological changes induced 
 by the bladder- worms of the eye are still more serious. This is true at 
 least of those which have taken up their abode within the eye, for in the 
 outer parts, and when easily accessible, the Cysticercusis not peculiarly 
 dangerous. The slight inflammations of the connective tissue which 
 may have been excited by the worm cease when it is removed. In 
 the orbifc the Cysticercus has been as yet certainly observed only in 
 the anterior division outside the muscular funnel. 2 The eyeball is 
 displaced by the growing tumour, and the conjunctiva is red and 
 sensitive. The thickness of the capsular wall and the occasional 
 formation of pus may be referred to an inflammatory reaction on the 
 part of the surrounding connective tissue. When the worm is lodged 
 in the depth of the orbit, the disturbances become still more serious, 
 
 1 Perls mentions a case in which thirty bladder- worms *ere extracted from an abscess. 
 "Pathol. Anat.," Bd. i., p. 80. 
 
 3 See Berlin in "Handbuch d. ges. Augenheilk. ," Bd. vi., p. 689. 
 
PATHOLOGY OF BLADDER-WORMS IN THE EYE AND BRAIN. 559 
 
 since in such cases the pressure of the tumour must act on the nerve, 
 causing pain, and impairing vision, if not producing blindness. 
 
 Among the different cases of intra-ocular Cysticerci, those are 
 certainly least serious in which the parasite occurs in the anterior 
 chamber of the eye. Not only can it be easily extracted, but its 
 presence seems to do little more harm than slightly impair vision, and 
 produce a more or less distinct irritation of the iris. 
 
 A Cysticercus in the fund us of the eye 1 has disastrous consequences, 
 especially in the subretinal tissue, for by the separation of the retina 
 and induced irido-choroiditis sight is in course of time almost wholly 
 lost. The trouble begins by a slight diminution in the power of 
 vision, but this is succeeded by a limitation or interruption in the 
 field of vision, which afterwards becomes a marked defect. After the 
 lapse of some months or even more, inflammation sets in, which spreads 
 to the front of the eye, especially to the iris, and passes through several 
 slow periodically aggravated stages, until finally a " phthisis bulbi " 
 results. More rarely an acute irido-cyclitis is the issue, and this may 
 culminate in panophthalmitis. A most violent ciliary neurosis is 
 associated with these processes, and persists perhaps for several years. 
 As a rule, the danger of sympathetic inflammation has before this 
 necessitated enucleation. When the Cysticercus passes early into the 
 vitreous humour the prognosis is somewhat less serious, especially if 
 the worm be en capsuled, as v. Graefe once observed. In such cases 
 the eye sometimes retains its outer form and a slight power of vision. 
 Usually, however, the retina undergoes separation, and here, too, a 
 gradual irido-choroiditis sets in, which usually ends as above described, 
 but sometimes acquires a more glaucoma tous character. 
 
 Important and interesting as are bladder-worms in the eye, they 
 are still more so in the brain, where they almost always cause serious 
 trouble. Among the cases collected by Kiichenmeister 2 there were 
 only sixteen which were not accompanied by pathological symptoms 
 during life. In six cases the troubles were slight, such as headache, 
 fatigue, lethargy, and giddiness ; twenty-four were cases of epilepsy 
 (eleven of which were characterised by psychical disorders) ; six were 
 cases of cramp, and forty-two of paralysis, of which seven were associated 
 with psychical disorders and ten with apoplexy, while twenty-three 
 were mental disturbances of varying intensity, and occurring partly 
 alone and partly combined with more or less radical nervous diseases. 
 
 We are indebted to Griesinger for an excellent discussion of these 
 pathological states, though this has been subsequently somewhat 
 modified by Kiichenmeister. 3 The former refers the phenomena te 
 
 1 See the reports of Leber and v. Wecker. 2 Loc. cit. 
 
 3 Archivf. HeUkunde, p. 207, 1862. 
 
560 OCCURRENCE AND RESULTS OF CYSTICERCUS CELLULOSE. 
 
 two groups, those caused by the wandering of the embryos, and 
 those determined by their permanent residence. The symptoms of 
 the first group are more or less inflammatory (headache, giddiness, &c.), 
 with the subsequent phenomena resulting from irritation and com- 
 pression of the brain. The patients are then usually induced to seek 
 medical advice. As a rule they also complain of attacks of cramp 
 and of mental disorder, of which the former are in all probability due to 
 the movements of the parasites, contraction of the caudal bladder, and 
 protrusion of the head. The diagnosis is not of course always equally 
 certain ; such symptoms might appear without the presence of bladder- 
 wprms. Specially dangerous are those attacks of more or less epileptic 
 cramp (without aura), which sometimes occur in later life without 
 obvious cause, and which either appear of a semi-acute character, or 
 rapidly succeed one another, increasing in number and intensity till a 
 very serious cerebral disease results. The mental disorders which 
 sometimes appear along with the epilepsy, or sometimes persist by 
 themselves, are generally of the nature of melancholia or mania. 
 Griesinger asserted that paralysis was a very rare consequence of 
 Cysticercus, but this is contradicted by Kiichenmeister's generalisations. 
 These paralytic consequences are indeed very varied ; they appear often 
 only after a long time ; they may be widely diffused or restricted to 
 particular parts ; but these differences are of secondary importance, 
 being determined by the number and position of the worms, or by 
 the nature of the affected nervous tissue. We know further that 
 Cysticerci in the brain are of fatal significance, not merely because of 
 their presence, but also because they soften the surrounding nervous 
 substance and lead to haemorrhage, and to other diseases, such as 
 meningitis, hydrocephalus, apoplexy, &c., which again induce other 
 disorders, often of very great extent. 
 
 "Where paralysis, even of slight character, occurs, the position of 
 the Cysticerci is almost always deep down ; when they are superficial, 
 other serious disorders ensue. In fact, in the latter case, paralysis 
 results only when the Cysticerci form round about them apoplectic 
 areas, or when by their position (say at the base of the hemispheres) 
 and size they are capable of exerting pressure even on the deeper 
 central portions. According to Kiichenmeister, on whose authority 
 these statements are mostly made, epilepsy has been observed almost 
 only in those cases where both hemispheres or ventricles, or when 
 unpaired organs, especially the pons and medulla, were infected. 
 The Cysticerci on the surface of the brain do not per se cause mental 
 diseases, except in cases of hereditary predisposition thereto, but these 
 seem to result especially when the cerebral ganglia, ventricles, and 
 choroid plexuses are attacked either by themselves or along with 
 
DESCRIPTION OF T^NIA ACANTHOTRIAS. 561 
 
 other parts of the brain. The intensity and exact nature of the 
 symptoms vary of course enormously. We must not for a moment 
 forget that we have not yet anything like sufficient data to determine 
 with any certainty the connection between anatomical and patho- 
 logical conditions in this matter. Still less can we understand the 
 physiology of such a connection. Since without further evidence, such 
 as the presence of bladder-worms in the skin or the eye, it is difficult 
 to be sure of their presence in the brain at all, it must be even more 
 difficult to determine the position and distribution of these worms. 
 
 As in so many other matters, we must look to the future, in 
 expectation of a deeper insight into the anatomical and physiological 
 facts of the case. 
 
 Taenia acanthotrias, Weinland. 
 
 Weinland, "An essay on the tape- worms of man," p. 64 : Cambridge, U.S.A., 1858. 
 ,, Med. Correspondenzbl. d. Wurtemb. drztlichen Vereins, No. 31, 1859. 
 ,, " Beschreibung zweier neuer Tanioiden des Menschen," Nova Acta Acad. 
 Cces. Leop.-CaroL, Bd. xxviii., Taf. i.-iii 
 
 Only the bladder-worm of this Cestode is as yet known. It is very 
 like Cysticercus celluloses, and lives like it in the muscles and brain of 
 man. It is distinguished ~by the structure of the hook apparatus, which 
 is composed of a triple circle of from fourteen to twenty-six somewhat 
 slender hooks. 
 
 The first observer, Jeffries Wyman, found it in a Virginian woman, 
 who was infested with Trichina, and who died of consumption. He 
 regarded it as Cysticercus celluloses, as did Weinland also, until he 
 discovered the remarkable structure of the hook-apparatus. 
 
 The reports made by Weinland on this interesting parasite I am 
 able to confirm, after examination of the only specimen which has 
 been seen in Europe, which was most liberally lent me by the owner, 
 my friend Weinland. I may also add that the head of this, as of 
 the ordinary bladder-worm from the muscles, is rolled up in the 
 receptacle like a snail, and has its apex impregnated with black 
 pigment granules. 
 
 The total number of hooks in the specimen I investigated was 
 forty-eight, while Weinland reports the number as forty-two. All 
 three forms of hooks are present in equal number, and the smallest 
 thus occur between every hook of the first row and the adjacent hook 
 of the second row on one side. In spite of the different sizes of the 
 hooks, their points all fall very much on the same line, which is due 
 of course to their being inserted at different levels on the rostellum. 
 The diameter of the latter and of each sucker is about 0'35 mm. The 
 
 2 N 
 
562 
 
 T^NIA ACAXTHOTRIAS. 
 
 length of the broad wrinkled body of the worm is estimated by 
 Weinland at about 10 mm. The bladder is as large as in Cysticercus 
 cellulosce. 
 
 FIG. 302. Cytticcrcu* acanthotricu. Head and circlet of 
 hooks seen from above, after Weinland. (x. 60. ) 
 
 The size of the hooks, according to my measurements, was some- 
 what larger than according to Weinland. According to me they 
 measured 0196, 0'14, 0'07 mm., while according to Weinland they were 
 only 0-153, 0*114, 063 mm. The length of the roots I estimated at 
 O'l, 0'07, and 0*035 mm., and the height from the point of the anterior 
 process upwards at 0*1, 0*08, and 0'045 mm. The posterior processes 
 were relatively longer than in Tcenia solium. The whole form is, as 
 we have seen, somewhat slender, and this applies to the processes 
 as well as to the hooks. The brown coloration of the root-processes 
 is striking, and at one position in the large hooks becomes developed 
 into a distinct black line. 
 
 FIG. 303. Hooks of Cysticercus acanthotrias, after Weinland. 
 (x 280.) 
 
 This Cysticercus acantkotrias represents an independent species, 
 and is not merely a malformed C. celluloses with supernumerary 
 
DESCRIPTION OF T^ENIA MARGIN ATA. 563 
 
 circlet of hooks, as has been lately asserted. 1 This is proved not 
 only by the form and size of the hooks, but also by the fact that 
 all the (8-10) specimens yet seen have exactly the same organization. 
 To doubt the value of this character is to question the specific nature 
 of almost every one of the Tcenicc. 
 
 The worms occurred in a white woman (not a negress) about 
 fifty years of age, and were from twelve to fifteen in number, being 
 all found in the connective tissue of the muscles and subcuticula, 
 with the exception of one, which hung freely on the inner surface of 
 the dura mater, near the crista galli. 
 
 The related Tcenia is unknown, but, from analogy, one is naturally 
 inclined to think that it lives in the human intestine like Tcenia 
 solium. If this be true, we should look for the bladder- worm also in 
 some other animal, such as the ox. 
 
 P Taenia marginata, Batsch. 
 
 Kiichenmeister, " Ueber die Taenia e Cysticerco tenuicolli, ihren Finnenzustand und 
 die Wanderung ihrer Brut," Moleschott's Unlersuch., Bd. i., pp. 256-378 : Frankfort, 
 
 1856. 
 
 The adult Tcenia, which is found in the dog and wolf, is distin- 
 guished from the other tape-worms parasitic in these animals, first by 
 its length, which attains to 2'5 mtr., but is usually little above 1*5 mtr. 
 The proglottides are also large, and thus it may be easily mistaken for 
 T. solium, though the habitat and the form of the hooks are different. 
 The quadrangular head has a diameter of about 1 mm. The suckers 
 are, on the whole, smaller and weaker than those of T. solium ; the 
 hooks are about the same size, but more slender, and provided with longer 
 roots. Their number is on an average from thirty six to thirty-eight, 
 the maximum being forty-two, the minimum thirty-two. The neck is 
 usually so slightly narrowed, that the head passes gradually into the 
 body without perceptible constriction. The segments begin a few milli- 
 metres behind the head, but only gradually increase in length, so that the 
 square form is attained somewhat late, at about the time of maturity, 
 and at a distance of about 50 cm. behind, the head in about the 550th 
 joint. The posterior border of the proglottis is prominent, overlapping 
 the anterior edge of the succeeding one, and is not unfrequently undu- 
 
 1 Thus Redon, Comptes rendas, t. Ixxxv., p. 676, 1877. In support of this 
 assertion he cites a case of Cysticercus cellulosce in which he counted forty-seven hooks 
 in three rows (?). The numbers given are somewhat unsatisfactory. Kiichenmeister seems 
 to share Redon's opinion (" Parasiten," second edition, p. 136), and would deduce it from 
 a Tcenia solium with six suckers. It is, however, difficult to see how the brood should 
 come to inherit, instead of six suckers, some forty hooks arranged in three rows. 
 
564 T^ENIA MARGINATA AND CYSTICERCUS TENUICOLLIS. 
 
 lating. The last proglottides have the form and size of those in the 
 smaller human tape-worms, having a 'breadth of 4 to 5 mm., and a 
 length of 9 toll mm. They contain a uterus, which is characterised partly 
 by the shortness of the median stem, and partly by the small number (at 
 most eight) of lateral branches, which have, however, strong and wide- 
 spread ramifications above and below. Tlie emfoyonic shells are round 
 (O036 mm.), thick, and covered by a distinct layer of rods, as in T. 
 solium. 
 
 The worm thus shortly described was first made known to us 
 by Kiichenmeister's breeding experiments. He termed it Tcenia e 
 Cysticerco tenuicolli ; after which I showed that it was identical with 
 
 FIG. 304. Hooks of Tcenia marginata. ( x 280.) 
 
 the T. marginata described by Batsch from the wolf. This Krabbe 
 and Kiichenmeister confirmed. The related bladder-worm (Cysticercus 
 tenuicollis) lives sometimes alone, sometimes in groups in the omentum, 
 and more rarely in the liver and other viscera, especially of ruminants 
 and swine. 1 It has an oval form, and an ap- 
 preciable, sometimes considerable, size. In the 
 larger specimens the anterior end of the bladder 
 is drawn out into a long, slender, neck-like pro- 
 cess, which bears the parenchymatous worm-body, 
 and encloses it in a sheath, when both are re- 
 tracted within the bladder. Then it forms a more 
 FIG. W$. --Cysticercus or i ess i ong r ibbon, hanging into the cavity of the 
 
 tenuKolhe, after Bremser f 
 
 (half size). bladder, in which it sometimes floats freely, or is 
 
 at certain points connected with the wall. 
 
 Since the Cysticercus tenuicollis is not a rarity in animals used as 
 food (also in deer and roes), and sometimes grows to the size of a 
 child's head, 2 we may readily suppose that it has been known for 
 
 1 Africa is also a home of the Cysticercus tenuicottis, as I have proved by the examina- 
 tion of a Cysticercus from Potamochcerus penicillatus, for which I am indebted to Dr. 
 Spencer Cobbold of London. 
 
 a Kuchenmeister even credits the bladder- worm with a length "of five feet," " Para- 
 siten,*' second edition, p. 138. 
 
HISTORY OF CYSTICERCUS TENUICOLLIS. 565 
 
 long. Yet there are but few hints of such knowledge, with the ex- 
 ception of Hartmann, who (in 1685) made his discovery of the animal 
 nature of the bladder- worm in connection with this very form. It is, 
 however, possible that the size and occurrence of this worm have led 
 to its being confused and ranked with Echinococcus. This has been a 
 serious source of error, even as regards its human pathology. On the 
 strength of certain cases, partly chronicled by Bonetus and partly the 
 subject of later observation, Cysticercus tenuicollis has often been 
 reckoned among the human parasites, especially under the title C. 
 visceralis. We must also concede that many of these cases admit 
 of such a construction, as those of Plater 1 and Koplin, 2 where re- 
 ference is expressly made to C. tenuicollis. The identity is never, 
 indeed, certain, so that the occurrence of the latter in man was re- 
 garded as a debateable point, as Eudolphi concludes, from the negative 
 results of over a thousand post mortem examinations. About twenty- 
 live years ago, however, it became apparently certain that Cysticercus 
 tenuicollis, which had meanwhile been observed in monkeys, was also 
 occasionally found in the viscera of man. This was the result of the 
 researches of Eschricht 3 regarding a number of bladder-worms which 
 were collected by the well-known Dr. Schleisner in his observations 
 on the Icelandic liver disease. Among these objects Eschricht 
 found, besides several Echinococci, also a Cysticercus tenuicollis. There 
 is no question as to the reality of this, but in consequence of Krabbe's 
 results, we are forced to the conviction that there was some confusion 
 or mistake in the sending of the worm in question. 4 In point of 
 fact, the C. tenuicollis has never been found in man by the Icelandic 
 physicians, 5 although the T. marginata is everywhere the most 
 frequent tape-worm in the dog, and an infection with its eggs could 
 hardly be any more difficult than with those of T. echinococcus. 
 
 Such being the case, and knowing that T. marginata never 
 develops as a tape- worm in man, as has been proved by the experi- 
 ments made on himself by Dr. Moller in Altona, 6 we might then 
 leave it out of account, were it not that the worm in its Cysticercoid 
 stage is of great interest both to pathologist and zoologist, and affords 
 
 1 Bonetus, " Sepulchretum," Obs. Lib. iii., p. 635. 
 
 2 Schriften d. Gesellsch. naturf. Preunde, i., p. 350. 
 
 3 " Undersogelser over den i Island endeiniske Hydatidensygdom," Danske Vidensk. 
 Selsk. Forhandl, p. 211, 1853. 
 
 " Rech. helmintholog. en Danemark et en Islande," p. 43 : Copenhagen, 186G. 
 
 6 Von Siebold thinks that the liver disease of the Icelanders must be wholly referred 
 to the parasitism of Cysticercus tenuicollis (" Band- und Blasenwurmer," p. 113). This 
 statement, however, is erroneous ; for even Eschricht, to whom v. Siebold refers, only 
 knew the one case above recorded, and rightly sought the cause of the disease in the 
 Echinococcus. 
 
 6 Kuchenmeister, loc. cit., p. 319, note. 
 
566 TCENIA MARGIN ATA AND CYSTICERCUS TENUICOLLIS. 
 
 a good illustration of what we have already said in connection with Cyst, 
 cellulosce, and shall again have to notice regarding the Echinococcm. 
 
 FurtJier Details regarding the Adult Tape- Worm. 
 
 Leuckart, " Blasenbandwurmer," p. 59. 
 
 Baillet, "Experience sur le Cysticercus tenuicollis," &c., Ann. sci. nat. (Zool.), ser. 4, 
 t. xvi., p. 99, 1861. 
 
 Krabbe, "Recherches helminthologiques," p. 3: Copenhagen, 1866. 
 
 In the alimentary canal of the dog there live, besides the above 
 described Tcenia marginata, 1 two other large-jointed, large-hooked 
 tape-worms, viz., T. serrata (e Cysticerco pisiformi) and T. ccenurus (e 
 Ccenuro cerebrali). These do not pass into man, 2 but are, neverthe- 
 less, worthy of mention if only because they have so often been 
 confused with one another, and with T. solium. The T. ccenurus, 
 besides, is among the most dangerous of all Helminths, because its 
 young brood causes the " staggers " of lambs, and thus inflicts great 
 loss upon the farmers. Formerly it was still more common, for we 
 now strive to protect our flocks from being infected by the dogs asso- 
 ciated with them. 3 
 
 As to the resemblance which T. marginata has both to T. serrata 
 and to T. ccenurus, this is most marked in the former instance ; for T. 
 serrata has almost the same external appearance and approximately 
 the same size (it is sometimes over a metre in length). T. ccenurus, 
 on the other hand, is full grown at a length of 30 to 40 cm., and, 
 besides this, remains much more slender than either of the others. 
 The chief differences, however, are seen in the structure of the head 
 (i.e., of the hook-apparatus) and of the uterus. 
 
 FIG. 306. Larger and smaller hooks of Tcenia serrata. ( x 280.) 
 
 Tcenia serrata has by far the largest head (1/3 mm.), the most 
 conspicuous suckers (04 mm.), and the strongest armature. The 
 
 1 In the countries where the reindeer abounds T. KraLbel is also found (p. 405, note). 
 
 8 The assertion that the Ccenurus also occurs in man is based on a misconception, 
 which arose from the unfortunate use which Zeder made of the same generic name (Poly- 
 cephalus) in reference both to Echinococcus and Ccenurus. 
 
 8 Through the kindness of the well-known breeder v. Nathusius-Hundisburg I am able 
 to state that he has thus reduced the disease from 20 per cent, to from 1 to 2 per cent. 
 
DIFFERENTIAL DIAGNOSIS OF T^INIA MARGINATA. 567 
 
 rostellum measures 0'64 mm., and bears a double circlet of from 
 thirty-eight to forty-eight powerful hooks, which (Fig. 306) are fully 
 a third longer and stronger than those of T. marginata. The total 
 length of the large hooks is about 0*25 mm., of the smaller 0*14 mm. 
 In the latter, the point of the anterior root is at an almost equal 
 distance from the two extremities (0'084 mm.), while the same distances 
 in the larger hooks are 01 mm. in front, and 0167 mm. behind. 
 
 In T. marginata the suckers and the rostellum measure about 
 0'34 mm. On the latter are from 32 to 42 hooks, which in form 
 (Fig. 304) are not unlike those of T. scrrata, but are less in strength 
 and size, having a length of only 019-0-21 mm. and 012-016 mm. 
 respectively. Specially distinctive are the comparatively great length 
 and the slender form of the anterior processes (compare Fig. 304). 
 This is most striking in the case of the small hooks whose anterior 
 root, as in the related species, has almost a Y-shape. The distances 
 between the two extremities of the hook and of the anterior root are, 
 in the larger hooks, about 0'09-01 mm. in front, and 011-014 mm. 
 behind, while in the smaller they sink to 0'077 mm. and 0'08 mm. 
 Between the hooks one sometimes sees (as also in the Cysticercus) 
 isolated black pigment granules, like those of Tcenia solium. 
 
 FIG. 307. Larger and smaller hooks of Tcenia ccenurus. ( x 280.) 
 
 The head of Tcenia ccenurus is of a more slender, pear-shaped form, 
 with a transverse diameter of O'S mm., and with somewhat insignificant 
 suckers (0'29 mm.). The rostellum has a diameter of 0'3 mm., and 
 carries usually twenty-eight (from twenty-four to thirty-two) hooks, of 
 which the larger are 016 mm. long, while the smaller measure only 
 01 mm. (Fig. .307). The distances between the extremities of the hooks 
 and the anterior process are in the larger hooks each 0'09 mm., and in 
 the smaller 0'084 mm. and 0'064 mm. respectively. Noteworthy, as 
 being diagnostic, is the heart-shaped structure of the anterior root on 
 the large hooks, and we have also to remark on the smaller and more 
 slender form of the posterior root. 
 
 But not only do these three worms differ from one another in 
 their external characters, and in the nature of the hooks, the liberated 
 proglottides also exhibit many differences in size and in the structure 
 of the uterus. 
 
568 
 
 TJENIA MARGIN ATA AND CYSTIC ERCUS TENUICOLLIS. 
 
 In regard to the differences in size, we must note that Tcenia 
 marginata liberates the largest and T. coenurus the smallest proglot- 
 tides. Those of the latter measure (without pressure) 5 to 6 mm. long 
 by 2'5 mm. broad ; in the former, the size is almost double (9-11 mm. 
 by 4-5 mm.). The proglottides of T. serrata are intermediate in 
 dimensions, and measure 8 mm. by 3 mm. 
 
 The structure of T. marginata has been already described. T. 
 serrata has more lateral branches (8-10 on each side), and a richer 
 and more irregular ramification. In T. ccenurus the number ascends to 
 from twenty to twenty-five, but they are somewhat simpler and shorter. 
 
 FIG. 308. Form of the uterus in different tape- worms. A, in T. terrata ( x 4) ; 
 , in T. marginata ( x 6) ; C, in T. coenurut ( x 10-15). 
 
 The eggs of the three species have a somewhat oval form, and are 
 almost equal in size, having a clear average diameter of 0*027 mm. 
 There are of course various divergences in points of detail, and 
 perhaps the eggs of T. coenurus are, on the whole, somewhat larger. 
 The embryonic shell has the familiar appearance, but its thickness, 
 especially in the case of T. ccenurus, is markedly inferior to that of 
 the eggs of the human tape- worm. In the size of the embryo and its 
 hooks these species are clearly allied to T. solium; in fact all the 
 cystic tape- worms (of the group Cystotcenia) differ in this respect only 
 in unimportant details. 
 
 Of course it is not only the free proglottides which thus differ 
 from one another, but also the " ripe " joints. Their number varies 
 not inconsiderably in the different species, the extremes being again 
 T. marginata, with not unfrequently fifty, and T. ccenurus, with hardly 
 ever more than a dozen. 
 
 It is evident that these differences must contribute to the above- 
 mentioned differences in size of the tape-worms of the dog. But 
 they are not the only factors affecting the latter. We must also 
 
STRUCTURE AND DEVELOPMENT OF CYSTICERCUS TENUICOLLIS. 569 
 
 take into consideration the fact that during the development and 
 gradual ripening of the proglottides a more or less extensive 
 growth takes place. In T. marginata there is between the first ripe 
 joint and the head a chain of 550 joints, of which the foremost are 
 of very inconsiderable length. In T. serrata there are about 325, 
 and in T. ccenurus hardly 200 segments. 1 
 
 I may now pass from the consideration of the anatomy of T. 
 marginata, especially since the character of the internal organs is 
 essentially the same as in T. solium. It is true that certain differences 
 in detail are not wanting, of which, however, I shall only mention 
 that the muscles of the body (as also in T. serrata), are more power- 
 fully developed than is the case in T. solium. Owing to this the 
 contractility of this tape-worm is much greater and more extensive 
 than that of the hook-bearing human tape- worm. The firm appearance 
 of the chain is also partly due to this circumstance. 
 
 Structure and Development of Cysticercus tenuicollis. 
 
 Like Tcenia marginata, which is in many respects very nearly 
 related to T. serrata, Cysticercus tenuicollis has a great resemblance to 
 C. pisiformis. This is especially true of its occurrence, and, according 
 to my investigations, of the events in its history. At first these 
 bladder- worms inhabit the liver, inside the branches of the portal 
 vein, which soon after the entrance of the embryos become choked 
 through the secretion of an exuded granular substance. Few only, 
 however, of the worms remain in this locality, most of them leaving 
 the liver before the development of the head, to remain for a time 
 .free in the body-cavity, and then to become encapsuled anew, gene- 
 rally in the mesentery. 2 
 
 The youngest specimens of Cysticercus tenuicollis hitherto observed 
 are those found by Leisering in a lamb, 3 which died ten days after 
 the feeding. Seen with the lens or with the naked eye, they 
 appeared as " small pale yellow points," which lay " in hundreds " in 
 the widely dilated ramifications of the portal vein. While the surface 
 was still uninjured, they could be driven out of one vessel into another 
 by careful pressure with the handle of the scalpel, and when a portion 
 of the larger branches of the portal vein was excised, they issued in 
 
 1 These numbers differ from Kuchenmeister's statements (according to which T. mar- 
 ginata possesses altogether only 400, T. serrata 286, and T. ccenurus 150 joints), only 
 because the anterior ones, which are certainly difficult to distinguish, have been overlooked. 
 
 2 For further information regarding the developmental history and fate of Cysticercus 
 pisiformis, see " Blasenbandwunner," p. 113. 
 
 3 Bericht iiber das Veterindnvesen Sachscns, p. 22, 1857-58. 
 
570 T^NIA MARGINATA AXD CYSTICERCUS TENUICOLLIS. 
 
 great numbers along with the blood. Unfortunately we still lack a 
 detailed description of these young bladder-worms. Not that there is 
 any doubt regarding their nature, for Leisering expressly mentions 
 that closer investigation showed them to be Cysticerci ; we have only 
 to regret the absence of fuller and more exact statements regarding 
 their size and structure. 
 
 In Leisering's case the lamb soon perished in consequence of the 
 feeding, and before the disease had led to inflammation. But that 
 the latter sometimes ensues is shown by the report of Kiichenmeister, 1 
 who made his first feeding experiments with Tcenia marginata, and 
 always lost his animals with violent symptoms of peritonitis. 
 
 I observed a very similar result in the case of a young pig, which 
 was procured from the country for helminthological experiment, but 
 which became infected spontaneously, probably while being brought 
 into the town. The animal began to ail in little less than two weeks, 
 and died some days later. On a dissection being made, the cause of 
 death was found to be a violent perihepatitis. The surfaces of the 
 liver, and especially the concave one, were covered with a thick white 
 deposit, in and under which at least 100 small specimens of Cysticercus 
 tenuicollis, with newly formed heads (6-8 mm. in diameter), were 
 embedded. Some were also found free in the body cavity, and others 
 were encapsuled in the omentum and in the lower parts of the lungs, 
 in which places they had always produced an inflamed circle of about 
 1*5 cm. in diameter. The intestines, which were matted together into 
 a coil, were strongly injected, and, like the liver, covered in many 
 places with a spotted layer of exudation. 
 
 In consequence of this experience, my animals were fed with only 
 a few proglottides, and it is owing to this circumstance that I have 
 never observed in them any symptoms of unhealthiness. On the 
 other hand, of course I found only a small number of Cysticerci, never 
 more than eight, and on one occasion only two. 
 
 The latter were found in the first animal experimented on, namely, 
 a young pig, which was killed twenty-three days after the feeding. 
 Even on cursory inspection, I saw here and there on the liver a 
 number of white streaks which generally issued directly from the 
 interior, and then sometimes ran for a time below the surface. Most 
 of these streaks were empty, but in spite of their considerable size, I 
 was able to, recognise them as worm-passages from the analogy which 
 they presented to similar structures found in the liver of the rabbit 
 after feeding with Tcenia serrata. Only in two of them there lay 
 enclosed within an egg-shaped distended space a clear transparent 
 
 1 Loc. ciL, p. 338. 
 
FORMATION OF WORM-PASSAGES IN THE LIVER. 571 
 
 globule, which, on closer investigation, proved to be a young Cysti- 
 cercus tcnuicollis. 
 
 The streaks were detached without great difficulty from the sur- 
 rounding parenchyma of the liver, and proved to be somewhat firm and 
 expansible cylinders, possessing a high degree of elasticity, and consist- 
 ing largely of a tough granular substance. The length of the cylinders 
 was from about 12 mm. to 15 mm., and their diameter between 1 mm. 
 and 1'5 mm., according to the place at which it was measured. 
 Instead of being regularly rounded, the streaks appeared almost 
 knotted, for they were either thick or thin, either constricted or pro- 
 vided with dilatations, which looked like knots, or with papillary 
 protrusions. Some of these protrusions formed true lateral branches 
 of a conical shape, which, after a short course, terminated in thin 
 solid threads. 
 
 I confess that the nature of these structures somewhat puzzled 
 me, until I discovered, while extracting one, that it was connected 
 like a twig with a large branch of the portal vein. The connection 
 was certainly not quite direct, since a short vascular process intervened 
 between the latter and the streak, but although distinctly marked off, 
 it passed continuously into the streak. Under these circumstances, 
 there could be no doubt that the streaks represented modified blood- 
 vessels, so that the Cysticerci occupied the same position as in 
 Leisering's case mentioned above. 
 
 The histological structure of the knot-bearing streaks was also 
 in agreement with this fact, inasmuch as the cheesy substance which 
 they enclosed contained, besides numerous granules and pus-corpuscles, 
 a number of uninistakeable blood-corpuscles. The dirty white or 
 yellowish walls of the streaks had certainly hardly any resemblance 
 to those of blood-vessels. They were much thickened and of an 
 almost structureless granular nature. At the most, one could only 
 perceive here and there a slight appearance of fibres. I must, how- 
 ever, remark that, on account of its indiarubber-like elasticity, the 
 tissue could only be submitted with great difficulty to microscopic 
 examination. 
 
 As has already been mentioned, most of the streaks were unten anted. 
 We must assume, however, that these empty streaks also had inmates 
 originally, but that, as so often happens in such experiments, the 
 worms had perished and disappeared. Only in two streaks had they 
 been preserved and developed into young bladder-worms. 
 
 The smaller of the two worms was a delicately walled, clear 
 globule, ovoid in form, and already of considerable size (6 mm. long, 
 3'5 mm. broad). It lay in an enlargement near one end of the other- 
 wise unaltered streak, and was surrounded on all sides by its granular 
 
- . r 
 
 572 T^NIA MARGIN ATA AND CYSTICERCUS TEXUICOLLIS. 
 
 contents. Although the head was wanting, the characteristic Cysti- 
 cercoid nature could be distinctly recognised. Not only did the worm 
 when pricked void a transparent non-granular fluid, but the charac- 
 teristic structure of the bladder was observable, and showed even 
 the larger and smaller vascular ramifications, with their ciliary lappets. 
 But, in spite of this, there was, as has already been mentioned, 
 no trace of the head. 1 Neither was there any trace of calcareous 
 corpuscles. The latter were also wanting in the second worm, although 
 this was in other respects more fully developed than the former, and 
 was especially characterised by the presence of a rudimentary head. 
 
 The length of this second worm was 8'5 mm., and its breadth almost 
 5 mm. The surrounding tube had, of course, been widened for the 
 reception of so large a body, and, being (Fig. 309) unable to resist the 
 pressure of the growing worm, it had burst along 
 half its length. From this rupture the anterior 
 portion of the bladder protruded like a hernia. 
 So much of the bladder-worm as remained within 
 the case was covered with a tolerably thick exuded 
 FIG. 309. Young Cysti- layer, the remaining portion being overlaid by a 
 
 **, t**uM, in .*. thin kyer Qf connective . tissue . 
 
 The tube which contained this second worm ran at a short distance 
 below the surface of the liver, and thus the superjacent parenchyma of 
 the liver was almost entirely displaced by the worm as it worked its 
 way out. The connective-tissue envelope of the latter was in contact 
 with the peritoneal covering of the liver, and this was even pushed 
 out into watch-glass-like protrusions by the pressure of the worm. 
 
 After the extraction of the bladder-worm, it was observed that 
 both its ends were not exactly of the same shape. The posterior end 
 was rounded, and the anterior conical. It is true that it appeared as 
 though this pointing were, partly at least, due to a contraction of the 
 circular muscular fibres. At any rate, the anterior end of the body 
 exhibited a more opaque appearance and a firmer consistency than 
 were observed elsewhere in the walls of the bladder. The head- 
 process had evidently been formed only a short time before. It was a 
 
 1 These young headless bladders are obviously those which, according to Kiichen- 
 meister, " always remain barren," and which he claims to be Acephalocysts of Cysticercus 
 tennicollis (loc. cit., p. 345). Kiichenmeister did not know that in this bladder-worm the 
 head is only developed at a later period, and he was somehow under a delusion when he 
 asserted that a cyst only about the size of a tare-seed contained a fully matured Cyst, tenui- 
 cottis. When, in express reference to my remark, Kiichenmeister afterwards declares 
 (" Parasiten," second edition, p. 139) that he must abide by his opinion, since the worms 
 in question were as yet only in " the (atoken = normal) Acephalocystic stage," he forgets 
 that he had previously expressly asserted that they were acephalocysts, " which always 
 remain barren." And it was only against that assertion that my remark was directed. 
 
STRUCTURE OF CYSTICERCUS TENUICOLLIS. 
 
 573 
 
 slender bottle-shaped appendage of insignificant length (1*3 mm.), 
 which hung clapper-like and in a longitudinal direction in the interior 
 of the bladder. The interior of the clapper was of considerable width, 
 especially at the posterior end, but otherwise it had ne very distinctive 
 feature. The receptacle appeared in the form of a thin layer, which 
 was in marked contrast to the rest of the head. 
 
 In a second pig, which had been fed a month before, the exit 
 from the liver, for which the first case was evidently a preparatory 
 stage, had just taken place. The Cysticerci, of which there were 
 four, were found free in the body-cavity. The former streaks had 
 disappeared, but in their place there were seen on the surface of the 
 liver four funnel-shaped pits, of appreciable width and more or less 
 considerable depth, out of which the bladder-worms had issued. The 
 borders of the place of exit were tolerably smooth and not much 
 injected, but deeper down there was to be observed a more or less 
 thick layer of a cheesy substance, evidently the remains of that 
 exuded mass which was found in the tubular streaks, and also in the 
 cysts formed by enlargements of the latter. 
 
 The length of the Cysticerci was 11 or 12 mm., and the breadth 
 5 mm. In this case also the anterior end was markedly narrowed, 
 but to different degrees in the different specimens. 
 The head-process had still the same slender form, 
 although its length was now 2 '4 mm., and the first 
 rudiments of the suckers and of the circlet of hooks 
 were already distinctly visible on its under end. It 
 is true that both these structures were as yet very 
 far removed from their ultimate form. The suckers 
 appeared simply as hemispherical protrusions on 
 the inferior flask-shaped enlargement of the cavity 
 of the head, and were for the most part still with- 
 out the subsequent muscular layer, which was 
 differentiated from the surrounding wall only in 
 one specimen. Similarly, the hooks were some- 
 times represented only by the claws, which, with 
 blunt base, were situated as little cones upon the 
 floor of the cavity of the head ; yet, in spite of their softness and the 
 thinness of their walls, they had already attained their subsequent 
 size and form. The calcareous corpuscles within the head were few 
 in number and of insignificant size. 
 
 It is hardly necessary to notice specially the differences between 
 the young Cysticerci and the muscle bladder-worms, especially of T. 
 solium. Apart from the actual history, the differences are indeed 
 marked enough, not only in the size and form of the bladder, but in 
 
 FIG. 310. ^, Young 
 Cysticercus tenuicollis 
 (nat. size) ; , the 
 head-process ( x 15). 
 
574 T.ENIA MARGINATA AND CYSTICERCUS TENUICOLLIS. 
 
 the position of the head-process and in the late period of its formation. 
 The straight position of the head lasts, however, only for a short time. 
 After the head is fully developed and its pedicel begins to grow, the 
 head-process in Cysticercus tenuicollis (Fig. 311) folds together in the 
 interior of the receptacle, just as in the majority of the other bladder- 
 worms. 
 
 Before proceeding, however, to the consideration of the other 
 changes undergone by the worms, I may mention that recently 
 Baillet in Toulouse has, by experimental investigations on Tcenia 
 marginata, obtained results which are strictly in accordance with the 
 preceding ones. Of these experiments, I shall only make special 
 mention of one which was made on a lamb. The latter received at 
 three different times, between the 4th and 10th of April, one, five, and 
 eleven proglottides of Tcenia marginata (T. Cysticerci tenuicollis, 
 Baillet). It became very ill on the fourteenth day after the feeding, 
 and died towards evening. On dissection there was found in the 
 abdominal cavity a considerable ecchymosis, which originated from 
 the numerous small streaks penetrating the congested liver. Each of 
 these streaks consisted of a tube, whose wall (unquestionably an 
 exuded layer) was easily distinguished from the parenchyma of the 
 liver, and whose blood-filled interior contained from one to four small 
 oval bladders. These measured from 0*6 to 3*5 mm. (or, in the smaller 
 diameter, 0*35 to 2 mm), and, in spite of the absence of a head-pro- 
 cess, were with all justice regarded as young bladder-worms. Some 
 of these streaks had opened externally, and had poured their contents 
 of blood and bladders into the body-cavity. Some young Cysticerci 
 were also found in the lungs and omentum ; in the former situation 
 generally in the centre of a more or less extensive ecchymosis. The 
 whole number was estimated at several thousands. 
 
 Thus it will be seen that the result of this investigation fills up, 
 in a very welcome manner, the gap between Leisering's experiments 
 and my own ; and as Baillet himself clearly states, gives fresh support 
 to the hypothesis of a wandering occurring through the blood-vessels. 
 Baillet's other experiments yielded much less striking results, and 
 also produced a much smaller number of bladder- worms (19, 1, 8, and 
 30), although the number of proglottides administered was not less 
 than in the first case. 
 
 As to the changes undergone by the worm after the transference 
 into the cavity of the body, I first succeeded in observing them in a 
 young pig, infected seven weeks previously, in which the bladder- 
 worms were about the size of a filbert (15 mm.), and were already encap- 
 suled in the omentum ; but that in this case also the original abode of 
 the worms had been the liver, was shown by the fact that its surface 
 
FURTHER DEVELOPMENT OF THE BLADDER-WORM. 575 
 
 exhibited stellate or linear scars, just like those found in the liver of 
 the rabbit after the exit of Cysticercus pisiformis. Besides this, the 
 connective tissue capsules of the mesentery were, on their internal 
 surface, without that granular exuded layer which was usually found 
 in the first breeding-place of the worm. Instead of it there was a 
 layer of slightly granular, clear, and pale balls, which in many re- 
 spects recalled pus corpuscles, and were about double the size of 
 blood-corpuscles. 
 
 I need hardly describe in detail the structure of the head pro- 
 cess. It consisted of an opaque mass of nearly spherical form, and 
 24 mm. in diameter, which was in marked contrast to the semi- 
 transparent bladder, and occupied the whole of the anteriorly pro- 
 jecting wart-like summit of the latter. The circlet of hooks, the 
 rostellum, and the suckers were fully developed. The body, closely 
 connected with the head, had a length of almost 4 mm., and a some- 
 what large transverse section. In histological respects, also, the head 
 had completed its development, as was sufficiently shown by the 
 distinct muscular fibres, calcareous corpuscles, and vessels. 
 
 I found bladder-worms in essentially the same condition in a 
 lamb three months after feeding. The only modifications worth 
 mentioning w r ere in the size of the bladder, which, with a breadth 
 of about 12 mm., had now grown to double the length, while in a 
 fresh condition its vessels could be plainly distinguished even by the 
 naked eye. Especially noticeable, as in Cysticercus cellulosce (p. 509), 
 were two irregularly branched longitudinal stems, which ran down 
 from the head-process towards the posterior end of the body, and 
 broke up into an extremely delicate net- 
 work. The external surface of the bladder 
 was traversed by fine longitudinal and 
 transverse wrinkles, which (perhaps in 
 consequence of the contraction of the 
 muscular fibres lying under them) were 
 closely crowded together. The head-pro- 
 cess and receptacle had exactly the pre- 
 vious structure. The former, in its 
 original invaginated state, with its bend- *>. j* 11 - A * Cysticercus tenui- 
 
 j , . . colhs, three months old (nat. size) ; 
 
 ings and tolds, filled up the interior of the B, The head-process (xio); a, 
 latter. It required a somewhat powerful rudiment of the ribbon-like process, 
 pressure to expel it, whereupon it of course turned its formerly interior 
 surface outwards, and assumed the attitude of the subsequent tape- 
 worm body. In this state the length amounted to between 5 and 6 
 mm., and its breadth at the lower end to fully 2 mm. 
 
 From the analogy between these bladder-worms and the related 
 
576 
 
 MARGINATA AND CYSTICERCUS TENUICOLLIS. 
 
 forms, we might now suppose that it had attained its complete deve- 
 lopment. But the investigation of older specimens proves the con- 
 trary. For not only does the bladder continue to grow until it has 
 attained the size of a goose-egg or more, but the head-process and the 
 point of attachment also undergo further modifications. 
 
 The most remarkable is that which has to do with the recepta- 
 culuvn. The posterior end of the latter grows into a solid process, 
 and ultimately forms the above-mentioned ribbon (p. 564), which is to 
 some extent a continuation of the head-process, and hangs down to a 
 variable distance in the interior of the bladder. I find the first 
 trace of this structure in the previously described bladder-worms; 
 sometimes, it is true, only in the form of a flat, hump-like projection, 
 which is situated on the receptaculum (Fig. 311 B, a), or rather it is 
 formed out of it by thickening and proliferation of the tissues. Even 
 later, this ribbon, in its histology, is most nearly related to the re- 
 ceptacle. Like the latter, it consists of connective-tissue, which is 
 penetrated by muscle fibres, and contains, besides a few isolated 
 calcareous corpuscles, numerous granular cells. The muscular fibres 
 run principally in the peripheral parts, while the granular cells are 
 deeper down, and are sometimes grouped together into a distinct axial 
 band. Where the ribbon, as sometimes happens, comes into union 
 with the inner surface of the wall of the bladder, the muscular 
 fibres are observed to pass directly into those 
 of the latter. The posterior end is some- 
 times cleft, and even separated into individual 
 fibres. 
 
 We can only briefly indicate the manifold 
 ways in which this structure has been mis- 
 interpreted both by earlier and later observers. 
 Besides, having been occasionally claimed as an 
 intestinal or sexual organ, it was also (unfor- 
 tunately by myself in 1848) associated with 
 the erroneous theory regarding the dropsical 
 origin of the bladder- worms, and was regarded 
 as the remains of the formerly solid tape-worm 
 body. On the contrary, it appears to be in 
 reality, in physiological as well as in morpho- 
 logical respects, a structure of subordinate 
 importance, and is, in short, only a somewhat 
 unimportant outgrowth of the receptacle a luxurious growth, similar 
 to that which sometimes originates in certain conditions in plants. 
 
 Even before the development of this process, the part of the 
 bladder where the receptacle is situated is generally prolonged into 
 
 FIG. 312. Longitudinal 
 section through the head of 
 an adult Cysticercus tenui- 
 cottis, with ribbon-like ap- 
 pendage on the receptacle 
 (after Moniez). (x 20.) 
 
DIMENSIONS OF CYSTICERCUS TENUICOLLIS. 577 
 
 a kind of neck, and drawn out into a hollow cylinder, which some- 
 times projects externally (Fig. 310, A), and is at other times retracted 
 (Fig. 313), so that the head-process is deeply sunk within the bladder. 
 Although the presence of this process has given rise to the specific 
 name of this bladder- worm, it is by no means a characteristic mark, 
 since it varies very much in development, and is sometimes altogether 
 wanting. I have, for example, seen bladder-worms 70 mm. long, 
 with a neck of the same length, and others in which the neck only 
 measured 5 mm. As a rule, the bladder- worms have long necks 
 (in the two specimens mentioned the neck measured 60 mm. in one 
 case, and 14 in the other) ; but, on the other hand, the contrary is 
 sometimes observed. 
 
 As the bladder- worm grows older, not only do the bladder and the 
 receptacle alter, but the whole head-process undergoes change. For 
 when the head-process has attained a certain size (as in Cysticercus 
 fasciolaris), it is protruded from the bladder by evagination, and ulti- 
 mately assumes the form of a wrinkled and somewhat solid cylinder 
 1 to 2 cm. in length, and situated at the end of the neck of the 
 bladder. Only the head-proper remains, as a rule, drawn in. 
 
 This appendage is, however, visible generally only in those cases 
 in which the neck of the bladder hangs freely outwards. If the 
 latter be invaginated into the interior of the bladder of the worm, 
 the body lies hidden in the interior of this neck as in a sheath. 
 At the posterior end, where it is connected with the base of the 
 sheath, one sees the floating gelatinous band issu- 
 ing from it, looking as if it were a direct con- 
 tinuation of the body of the worm. The 
 receptacle as such is no longer present. It has 
 apparently been invaginated along with the head, 
 and has probably been used in the progressive 
 solidification of what we have seen to be origi- 
 nally a tubular body. 
 
 It is not known to what age Cysticercus tenui- 
 collis may live, but it appears almost as though FIG. 313. Anterior 
 it might exist uninjured for many years. At least end . of Cysticercus tenui- 
 this may be supposed from the colossal size which nec k,' and ribbon-like 
 the bladder -worm sometimes attains. The appendage. 
 Giessen zoological collection possesses a specimen, procured from an 
 ox with retracted neck, which is 160 cm. long and from 6 to 7 cm. 
 thick ; and Diesing has reported a specimen taken from a pig, which 
 was almost a foot long, 1 and had a diameter of 4 inches. The true 
 
 1 Could that have been the specimen of "five" feet mentioned by Kuchenmeister 
 ( " Parasiten," p. 517.) ? 
 
 2 
 
578 DESCRIPTION OF THE 8UBGENUS ECHINOCOCCIFER. 
 
 tape-worm is, however, of small size, even in such colossal specimens, 
 and is hardly longer than 10-15 mm. even when extended. 
 
 The form as well as the size of the bladder is subject to many 
 variations. This is especially true of the ratio between the length 
 and the transverse diameter, which varies so much that the worms are 
 sometimes spherical and sometimes longitudinally extended. Moniez 
 mentions a specimen which was from 6 to 7 cm. in length, but hardly 
 1*5 cm. broad. Under these circumstances, one might almost guess 
 that the Cysticercus fistularis from the horse, described by Eudolphi 
 as possessing a length of 4 to 5 inches and a breadth of 3 to 4 lines, was 
 nothing else than a longitudinally extended Cysticercus tenuicollis. 
 In another specimen, Moniez observed at some distance behind the 
 head a rag-like thickening of the bladder-wall, which measured almost 
 3 mm., and in its histological relations might be compared with a 
 segment of a Toenia. I owe to the kindness of Dr. Schmidt in Frank- 
 fort a Cysticercus tenuicollis of moderate dimensions, whose interior 
 contained three sterile daughter-bladders of 2 to 3 mm. in diameter, and 
 which thus in some respects furnished a counterpart to the Cysticercus 
 racemosus already described (p. 554). 
 
 In the dog the whole body of the bladder-worm is destroyed after 
 the feeding except the head and its neck. It is true that the solid 
 body of the worm is preserved for a time, and perhaps even longer 
 than in other bladder-worms, but this is not of the least significance 
 to the later Tsenioid body. From ten to twelve weeks generally elapse 
 before the expulsion of proglottides, while T. serrata only requires 
 eight weeks, and T. ccenurus becomes ripe even in three or four. 
 
 B. Cystic Tape- Worms, vihose heads are "budded off from special brood- 
 capsules attached to the inner surface of the bladder. 
 
 Subgenus Echinococcifer, Weinland. 
 
 J. Mttller, Archiv f. Anat. u. Phyt., p. 107, 1836; MtttheU. VerkandL GescUsch. 
 naturf. Freunde, p. 17, 1836. 
 
 Von Siebold, Burdach's " Physiologic," Bd. ii., p. 183, 1837. 
 
 Huxley, " Anatomy and Development of Echinococcus veterinorum," Proc. Zod, 
 Soc., xx., p. 110, 1852. 
 
 G. Wagner, " Entwickelung der Cestoden," Nova Acta Acad. Cces. Lcop.-CaroL, Bd. 
 xxiv., Suppl., p. 34, 1854. 
 
 Eschricht, "Beretning om fortsatte UndersSgelaer af Echinokokkerne, " Overs, k. d. 
 Vid. Selsk. Fork., p. 127 ; Zeitsckr. f. d. ges. Naturwiss., p. 231, 1857. 
 
 Krabbe, " Recherches helminthologiques en Danemark et en Islande," Copenhagen, 
 1866. 
 
 In the cystic bladder-worms of the previous group the tape-worm 
 head originated from a hollow process, which might be regarded as 
 an invagination of the bladder-wall. In the worms of this second 
 
FORMATION OF THE HEADS IN BROOD-CAPSULES. 579 
 
 group the heads are developed as before from hollow processes hang- 
 ing down into the cavity of the bladder, but these processes are not 
 seated directly on the wall of the bladder-worm, but on special small 
 brood-capsules, which attain about the size of a pin's head, and are 
 budded off in ever-increasing numbers from the inner surface of the 
 worm. The cuticle of the bladder, which is 
 distinguished by considerable thickness, does 
 not take the least share in these processes. 
 Sooner or later, sometimes only after complete 
 development, the heads become invaginated 
 into the interior of the brood-capsule, and 
 there become solid. The place of insertion 
 becomes changed into a thin stalk, which en- 
 closes the vessels of the tape- worm head. The 
 number of heads becomes continually greater 
 with increasing age, and sometimes amounts to FIG. 314. Brood-cap- 
 
 - . i i j i su l e of Echinococcus with 
 
 twelve or more in a single brood -capsule, retracted head and with two 
 Since the bladder, in contrast to the tape- worm appended buds at different 
 head, has attained a very appreciable size, and 
 
 often bears many thousands of brood-capsules, the total number of 
 heads is, of course, extremely large. The older heads not unfrequently 
 fall from their stalks, and waste away within the brood-capsule, but 
 this does not counterbalance the new growth. The total number of 
 heads always becomes larger with increasing age. In some cases it 
 may, without exaggeration, be estimated at several hundred thousands. 
 
 On the other hand, it must be remarked that the formation of 
 brood-capsules and heads is referred to a later period than is usually 
 the case with the cystic tape-worms. One not unfrequently finds 
 Echinococci the size of a pigeon's egg, which as yet contain no brood, 
 and others which remain sterile throughout life. 
 
 As to the histology of these animals, besides the above-mentioned 
 thickness of the cuticle, we should also note the extremely sparse 
 development of muscular fibres in the wall of the bladder, in con- 
 sequence of which the Echinococci have no power of vigorous move- 
 ment. They are as a rule motionless, so that at first sight one might 
 easily take them for simple water-bladders. And this is all the easier, 
 since they are distinguished from the other bladder-worms by very 
 frequently containing (and especially when occurring in man) a 
 varying number of small water-bladders (the so-called " daughter- 
 bladders" or "secondary hydatids"). We shall afterwards return to 
 these structures, and especially to the discussion of their remarkable 
 origin. Meanwhile we shall only mention that in the last case they 
 are the result of a budding, which is not unfrequently repeated in 
 
580 DESCRIPTION OF THE SUBGENUS ECHINOCOCCIFER. 
 
 such a manner that the original Echinococcus is changed into a system 
 of cysts enclosed one within another. These resemble vesicles of 
 Volvox, to which this parasite has indeed often been compared, and 
 represent so many generations enclosed one within the other, and 
 capable of producing tape- worm heads in the same manner as the 
 mother-bladder. In other cases, as we shall afterwards see, the 
 process of proliferation yields buds, which make their way outwards, 
 and are developed beside, the mother-bladder. 
 
 The Tcenice, which are developed from the Echinococcus-heads in 
 the intestine of the dog and related animals, are extremely small, and 
 have but few joints ; so that in this respect there is a striking differ- 
 ence between them and the cystic tape-worms of the previous group. 
 The hooks are proportionate in size to the head, but are otherwise 
 formed like those of the cystic tape-worms. 
 
 Whether there are several species of Echinococcus is a question that 
 has been much discussed by investigators. The early helminthologists 
 (with Rudolphi at their head) generally accepted two species, 
 Echinococcus hominis and E. veterinorum, which differed principally 
 in that the former contained numerous daughter and granddaughter 
 bladders, while the latter consisted usually of a simple bladder. It 
 has long since been proved, however, that the composite form, Echino- 
 coccus hominis, is also occasionally found in the ox and other mammals 
 (such as the horse, pig, and kangaroo) ; and, vice versa, that the human 
 Echinococcus not unfrequently possesses the simple structure of the 
 E. veterinorum. Sometimes one even finds two forms of Echinococcus 
 side by side in the same individual. 1 It has also been repeatedly 
 noted that it is difficult to differentiate the two forms sharply from 
 each other, since the number of the daughter-bladders varies consider- 
 ably, being sometimes very large, and at other times limited to a few, so 
 that the compound Echinococcus gradually changes into the simple one. 2 
 
 On these grounds many distinguished helminthologists (such as 
 my uncle F. S. Leuckart, Creplin, v. Siebold, and Diesing) have denied 
 that there is any warrant for the separation of these two species, and 
 have explained the indicated differences as mere individual varieties. 
 But at a later period Klichenmeister 3 has again spoken in favour of 
 the old idea, except that he changes the specific names Echinococcus 
 
 1 This sometimes happens in the pig, as is shown by Dupuy's case, quoted by Davaine 
 (Journ. mM. de Sedittot, t. xcii., p. 63, 1823). In the different muscles, in the lungs, 
 liver, and kidney, Echinococci were found, some of which were solitary, whilst others 
 enclosed daughter-bladders within them. 
 
 2 Eschricht mentions a case (of Krabbe's) in which an Echinococcus of the size of a 
 child's head only contained two small free-swimming bladders. A counterpart is furnished 
 by those cases in which the number of the endogenous bladders might be estimated at 
 several thousands. 
 
 3 "Parasiten," first edition, p. 139. 
 
VARIATIONS IN THE FORM OF THE HOOKS. 
 
 581 
 
 hominis into E. altricipariens, and E. veterinorum into E. scolecipariens. 
 He supports his opinion not only by a reference to differences in the 
 process of proliferation, but also by the statement that both species 
 present decided differences in number, size, and in the form of the 
 hooks. Echinococcus scolecipariens has, according to Kiichenmeister, 
 twenty-eight to thirty-six hooks of a stouter form, while E. altrici- 
 pariens has between forty-six and fifty-six, which differ markedly 
 from those of the latter in their slender and elegant structure. 
 
 If Kiichenmeister were correct in these observations, hardly any 
 objection could be raised against the specific nature of these two forms. 
 But such is not the case : not only does the number of hooks vary in 
 both of them between the two extremes (especially those which lie 
 further from each other, as in most of the other bladder- worms), but 
 the form of the hooks by no means exhibits any decided differences. 
 In comparing the two species, we ought always to go back to 
 equivalent stages of development. But if, like Kiichenmeister, we 
 neglect to do so, and compare the tape-worm taken from E. veterinorum 
 
 FIG. 315. Echinococcus hooks ( x 600). (A.) Of Echinococcus 
 veterinorum; (.) Of Tcenia echinococcus in the third week; (C.) Of 
 adult Tcenia echinococcus ; (D.) The three different hook-forms drawn 
 one within the other to show their gradual changes. 
 
 with the rudimentary head of E. hominis, we shall indeed see very 
 striking differences of form ; but, according to my observations, these 
 differences are to be explained by the fact that the Echinococcus-hooks 
 only attain their full development during the transformation of the 
 
582 DESCRIPTION OF THE SUBGENUS ECHINOCOCCIFER. 
 
 rudimentary head into the segmented tape-worm. I have established 
 this fact by comparison of the hooks of the Echinococcus from the cow 
 with those of the tape- worm from the same parasite, and in unripe 
 Tcenice (of the third week) I found perfect intermediate forms between 
 the structure of the Echinococcus-hQ&d and the developed Tcenia. 
 
 As is sufficiently shown in the preceding figures, the difference 
 between the hooks of the bladder-worm and those of the Tcenice of 
 Echinococcus have to do exclusively with the roots. The structure 
 of the claws is the same in both, but the root-processes are short and 
 slender during the bladder-worm stage, while in the adult tape-worms 
 they are not only considerably longer, but have also a stouter form. 
 Sometimes even in hooks of the same Tcenia one finds differences 
 in the length and thickness of these processes, and similar differences 
 are to be found in the Echinococcus-hQ&fa. In rare cases I have seen 
 in the latter an approximation to the form of the tape-worm hooks, 
 i.e., to a more perfect development of the roots. 
 
 This late or even secondary development of the hooks in Echino- 
 coccus brings it to pass that the roots are characterised by an other- 
 wise hardly perceptible variability in size and form. It is only 
 necessary to take a cursory glance at the examples given by Krabbe 
 on the third plate of his memoir on Echinococcus, in which there are 
 displayed not less than forty-two figures of large and small hooks, 
 showing how widely the extremes may differ from one another. 
 Many of the forms may indeed be explained as malformations, but 
 the frequent occurrence of others proves them to be normal. If we 
 compare them more closely, we soon see that the deviations consist 
 mainly in the more or less abundant deposit of chitin on the roots 
 of the hooks, through which deposit the latter sometimes increase in 
 length, and sometimes become gnarled and thickened. 
 
 With the demonstration of this late development, the most im- 
 portant of Kiichenmeister's arguments in favour of the validity of his 
 species lose their cogency, and they were indeed the only arguments 
 which we had to consider in deciding this question, for the above 
 mentioned differences in proliferation were from the first seen to have 
 only a doubtful value. 
 
 Such being the state of the case, even in the first edition of this 
 work, I expressed myself most decidedly against Kiichenmeister's 
 opinion, and maintained that the various forms of bladder- worm were 
 only varieties of a single species. The proposed change was not only 
 of fundamental importance in reference to our opinions as to the 
 nature and history of Echinococcus, but had a further practical im- 
 portance since Kuchenmeister claimed for his two species two different 
 tape-worm forms, differing not only in structure, but also in host. 
 
HISTORY OF THE ECHINOCOCCUS. 583 
 
 There were, in other words, two distinct sources, from either of which 
 man might be infected. 
 
 Being unable to identify the hypothetical Tcenia of Echinococcus 
 altricipariens with T. echinococcus, Kiichenmeister maintained on 
 purely theoretical grounds that the former lived preferably in the 
 human intestine, 1 and that thus the Echinococcus altricipariens, which 
 is by far the commonest form of the human Echinococcus, sprang from 
 a human tape-worm, and was perhaps only rarely brought to us 
 through the dog. My opinion has, however, in course of time, found 
 not only acceptance, but experimental demonstration. This has been 
 supplied by the above-cited observations of Krabbe, to which I may 
 again refer as important completions of my own researches. 
 
 Even Kiichenmeister has not been able any longer to resist the 
 force of established facts. In the new edition of his work on 
 parasites 2 he concedes with apparent unwillingness that the different 
 forms of Echinococcus are but varieties of the same species (T. 
 echinococcus). 
 
 Since the Echinococcus-bldiddQTS have almost no power of motion 
 in consequence of the considerable thickness of the cuticle, and the 
 extremely slight development of their muscle-fibres, and since their 
 heads are only recognisable on microscopic examination, we can 
 understand that their animal nature was established somewhat later 
 than was the case with the other bladder - worms, though their 
 existence and medicinal importance were much sooner recognised. 
 Even in Hippocrates we find passages which refer to this Echinococcus, 
 and in the writings of the physicians of the sixteenth and seventeenth 
 centuries we find descriptions of the so-called "Hydatids," which 
 give a correct and full statement of the external characters of the 
 organism. 3 Pallas was, however, the first (1767) to recognise in these 
 vibrating hydatids independent organisms allied to the bladder- 
 
 1 We shall afterwards see that Kiichenmeister has not even yet shaken himself free 
 from this utterly groundless opinion. 
 
 2 On page 162 he says, "I do not by any means contend that all the varieties of 
 Echinococcus represent distinct species of Tcenia." For one who formerly maintained 
 unequivocally the specific distinctions between these "varieties," this is a withdrawal 
 without any express acknowledgment of error. The change in the form of the hooks, so 
 characteristic of T. echinococcus, receives no further mention, except what we find on page 
 136, where Kuchenmeister, in discussing the question whether the differences in the 
 structure of the hooks between Cysticercus acanthotrias and C. ceUulosce are sufficient to 
 establish a specific distinction, says, " If the structure of the hooks in the different forms 
 of T. echinococcus be considered as varying with the individual hosts, and not merely with 
 their systematic position (sic/), the same view might be adopted here." 
 
 3 Other such cases are collected by Pallas (Neue nord. Beitrdge, Th. i, p. 84), by 
 Leuckart (" Blasenbandwurmer," p. 4), Davaine (loc. cit., p. 350), and by Kuchenmeister 
 ("Parasiten," second edition, p. 56, note), and still more thoroughly in the Deutsch. 
 Archivf. Geschichte d. Med., Bd. ii. u. iii. 
 
584 DESCRIPTION OF THE SUBGENUS ECHINOCOCCIFER. 
 
 worms, 1 while in 1781 the "balls" therein contained were ranked 
 along with the Ccenurus-he&ds which had been just discovered by 
 Leske. 2 The proof of the correctness of this opinion was furnished 
 by Goze, who in 1782 showed that the heads really belonged to 
 Tcenice, and possessed suckers and hook-apparatus, and also soon 
 recognised that they were independent forms, and could not be 
 ranked beside the " white bodies or worms in the brain of the sheep 
 afflicted with staggers," since they were "several hundred times 
 smaller." 3 And this was applied not only to the Echinococcus of the 
 cattle, but also to that of man, and that through a specimen which 
 the elder Meckel had sent for closer scrutiny to the indefatigable 
 helminthologist and pastor at St. Blasius in Quedlinburg. 4 Sub- 
 sequent observers were not all equally successful in their search for 
 these heads, and thus it happened that some even disputed the 
 existence of real Echinococci in man, 5 and, like Laennec, regarded 
 the bladders as a special animal organism (Acephalocystis) which 
 stood in the lowest rank of animal life, and in a certain sense filled 
 up the gap between the inanimate serous cysts and the ordinary 
 bladder- worms. 
 
 In many cases these so-called " acephalocysts " were, indeed, 
 nothing else than hydatid-like pseudoplasms, which had, of course, no 
 connection with animal parasites, and were readily distinguished 
 from the Echinococci, not only by their continuous connection with 
 the surrounding tissue, but also histologically and chemically by the 
 nature of their bladder-wall. 
 
 Although Bremser in 1821 again proved that the encapsuled 
 Echinococcus-\>lsi&deT9 of man had heads as well as the so-called E. 
 veterinorum, yet, till within a few decades, the old opinion was still 
 maintained, that there were acephalocysts representing a special 
 
 1 Stralsunder Magazin, i., p. 81. "It seeing to me very probable," he says, "that 
 the incompletely developed water vesicles seen by many observers in the human body, 
 such as those oftenest found in pathological cavities in the liver, are caused by and arise 
 from a worm resembling our own tape- worms (i.e., Tcenia hydatigena Cysticercus)." 
 
 * Neue nord. Beitrage, Th. i., p. 85. 
 
 3 " Versuch einer Naturgesch.," p. 158. 
 
 4 This is the same case which gave rise to the above-mentioned opinion that Coenurus 
 occurred in man an opinion still strangely maintained by Kiichenmeister ("Parasiten," 
 second edition, p. 57). It " was for long indeed " generally accepted, until Rasmussen 
 (1865) distinctly proved that it "referred to an Echinococcus given by Meckel to Goze, 
 and found among the effects of the latter." Kiichenmeister seems to have entirely over- 
 looked the above passage quoted verbally from the older edition of this work. 
 
 6 The word Echinococcus, strictly speaking, is applicable only to the head, and was 
 formerly so used. 
 
 6 " Me'm. sur les vers viscer. et principal, sur ceux qui se trouvent dans le corps 
 humain : " Paris, 1804. 
 
FERTILE ANt) STERILE ECHINOCOCCI. 585 
 
 animal form. 1 This report received strength from the fact that 
 some Echinococci have really but few or even no heads in their 
 bladders. This loses all importance, however, when one sees that in 
 the encysted Echinococci sterile bladders are sometimes found in the 
 same cyst with proliferating ones. The sterile bladders are, further, 
 not merely smaller, half abortive forms, so that they might be held as 
 immature, but on the contrary, they are not unfrequently the larger. 
 
 I do not for a moment doubt that the imperfectly developed 
 Echinococci have often been regarded as acephalocysts. 2 From my 
 experimental observations I may consider it as settled that the heads 
 of the Echinococcus-bl&ddQis are formed much later than those of the 
 Cysticerci, at a time when the young worms have already grown to a 
 considerable size. Such immature Echinococci must therefore be 
 observed all the more frequently, since the development of these 
 animals takes an unusually long time. The Echinococcm-\)l&ddeTS 
 grow for fully four months and more before they are capable of pro- 
 liferation, and have then attained the size of a small walnut. This 
 is, of course, true only of those worms which develop from the six- 
 hooked embryos : for in the daughter-bladders, and in those budded 
 off on the outside of the mother-cyst, I have sometimes seen brood- 
 capsules of the size of a hazel-nut and less with heads inside them. 
 
 The sterile Echinococci remain throughout life at an early stage 
 of development. They are like trees which never bear floweis or 
 fruit. In plants, sterility usually depends on the conditions under 
 which they live, and the same may be true of the Echinococci. In 
 point of fact, it has been repeatedly observed that in certain localities 
 the Echinococci are much oftener sterile than in others, the Echinococci 
 of the brain, e.g., more frequently than those of the liver, &c. 3 In 
 man this sterility is not unfrequently associated with the absence of 
 daughter-bladders, which is certainly a renewed caution not to em- 
 phasise too strongly the vegetative conditions in judging of specific 
 distinctions. Thus, in a case 'described by Charcot and Davaine 4 of 
 
 1 See Tschudi, " Blasenwtirmer," p. 28. On the other hand, the animal nature of 
 these so-called "acephalocysts" is often distinctly denied, e.g., by Rudolphi, Blumenbach, 
 Heusinger, &c., and for a while by Kuchenmeister. But the latter was, as he himself 
 remarks ("Cestoden," p. 6, note), first convinced of his mistake by my demonstration of 
 the chitinous nature of the bladder- wall. And yet he sometimes gets the credit of being 
 the first to establish the true nature of the acephalocysts. 
 
 2 Thus, e.g., by Kuhn, whose figures exactly correspond with the Echinococci, four 
 months old, of my rearing ("Rech. sur les ac^phalocysts, " Mem. Soc. hist. nat. Strassb., 
 t. i., 1830). 
 
 3 On the whole, the importance of these results is but slight, as is evident from the 
 fact that the presence of heads and hooks is noted only in a very small minority of the 
 cases of human Echinococci. 
 
 4 Mem. soc, UoL, p. 107, 1857. 
 
586 DEFINITION OF T^NIA ECIIINOCOCCUS. 
 
 multiple Echinococci in the liver and other viscera, all the cysts which 
 lay under the peritoneal coating of the intestine, and were connected 
 with it only by a more or less long, thin stalk, were devoid of daughter- 
 bladders and heads (or had only very small ones), while all the others 
 exhibited the normal structure. 
 
 The rarity of the heads is also the reason why the true nature of 
 the so-called " multilocular " Echinococcus was misunderstood, until 
 Virchow's researches. * The small component bladders used to be con- 
 sidered as colloid masses, and the whole as an alveolar colloid cancer. 
 
 Taenia echinococcus, von Siebold. 
 
 Von Siebold, "Ueber die Verwandlung der Echinococcusbrut in Tanien," Zeitscltr.f. 
 wiss. Zool., Bd. iv., p. 409, 1853. 
 
 A tape-worm of comparatively small size, and with only three or 
 four joints, of which the last, when mature, exceeds all the rest of the 
 body in size. The total length is only a few (at most 5) millimetres. 
 The small hooks have stout root-processes, and are seated on a somewhat 
 swollen rostellum. Tlieir number usually amounts to some thirty or 
 forty. 
 
 The young stage, long known under the name Echinococcus, forms 
 very conspicuous, almost motionless bladder, with a thick, elastic, 
 and frequently laminated wall, on whose inner surface, in special 
 brood-capsules of the size of a millet-seed, there are budded off 
 numerous small heads, almost invisible to the naked eye. Not un- 
 frequently the bladder increases by budding either externally or in- 
 ternally; it may thus become a composite system of larger and 
 smaller bladders, one within the other. Such bladders are found 
 especially in man and the ox, while other ruminants swine and 
 monkeys usually harbour either simple bladders, or those with 
 exogenous multiplication. 2 The favourite place for the Echinococcus 
 is the liver or lungs ; but there is hardly an organ which may not 
 harbour it. The adult tape-worm lives socially in the intestine of 
 the dog, jackal (Panceri), and wolf (Cobbold). 
 
 Description of the Adult Tape- Worm. 
 
 The head of Tcenia echinococcus is characterised not merely by its 
 small size (its transverse diameter is scarcely 0'3 mm.), but also by 
 
 1 Verhandl. d. med. phys. Gesettsch. z. Wiirzburg, Bd. vi., p. 84, 1855. 
 
 2 With the exception of the peacock, in which an Echinococcus was detected by v. 
 Siebold, and lately again by Pagenstecher, mammals are the only hosts of this worm. I 
 may here mention as well the occurrence of an Echinococcus in the liver of a squirrel, 
 which I found noted in one of my uncle F. S. Leuckart's papers. 
 
 
 
FORM AND SIZE OF THE HEAD AND HOOKS. 
 
 587 
 
 the possession of a somewhat prominent crown (0*13 mm. broad) 
 which surrounds the bulging rostellum. The hooks borne by the 
 rostellum form, as in the other cystic tape-worms, two series of from 
 
 FIG. 316. Adult Tcenia 
 echinococcus. (x 12.) 
 
 FIG. 317. Echinococcus veterinorum (nat. size and 
 position). 
 
 fourteen to twenty-five each, but they are rarely found in a perfect 
 state. The hooks are characterised by the thickness and solidity of 
 their roots (Fig. 315, <?). In details they vary widely even in the 
 same worm. 
 
 Those of the inner series are, as usual, the larger, and when full- 
 grown attain a length of 0*04 to 0*045 mm. More than half of this 
 is formed by the roots ; the distance of the point of the anterior root 
 from the posterior end is 0*025 to 0*028 mm., and from the anterior 
 end only 0*017 to 0*019 mm. The claw is slender, and somewhat 
 strongly curved. The roots appear somewhat thicker and stouter, 
 inasmuch as the saddle-like notch between them is often more or less 
 completely filled up. The back of the posterior root not unfrequently 
 shows in the middle a shallow, curved cleft. The hooks of the second 
 series are not only smaller (0*030 to 0'038 mm. long), but have a 
 thinner posterior root, compared with which the markedly projecting 
 anterior root has an almost discoidal form. The distance of the end of 
 
588 DESCRIPTION OF THE ADULT T&NIA ECHINOCOCCUS. 
 
 the anterior root from the point of the hook is 0*013 to 0*015 mm. ; 
 from the posterior end of the hook, 0*022 to 0'025 mm. 
 
 Behind the four 1 plainly muscular suckers (0*13 mm. in diameter) 
 the head narrows to a neck about 0*25 mm. thick, which then passes 
 without distinct boundary into the unsegmented anterior part of the 
 body. The first segment is but faintly marked off, being scarcely 
 broader than the preceding portion of the body, and almost as long 
 as broad. In the second segment the breadth has been doubled, and 
 the length increased four times, while the male and female reproduc- 
 tive organs can be distinguished a peripheral cirrhus, a vas deferens, 
 and eggs which collect in the uterus in the middle of the joint, and 
 sometimes already exhibit the first signs of embryonic development. 
 The third and last joint exhibits all the characters of maturity. It 
 has not merely grown to be 2 mm. long by 0'6 mm. broad, but is 
 also provided internally with hard-shelled eggs, which enclose the 
 familiar six-hooked embryos, and, according to the computations of 
 Johne and Kiichenineister, are about 500 in number. 2 In isolated 
 eggs one can distinguish, besides the hard shell, also the outer clear 
 egg-membrane, which is so distant that the total diameter is 0'065 mm. 
 The form of the uterus is moderately simple ; one can recognise a 
 wide median stem, with several diverticula or short, slightly ramified 
 lateral branches. In spite of the minuteness of the tape-worm, the 
 eggs have the ordinary size, but the shell is comparatively thin, and 
 is but faintly granulated on the outer surface. The internal space is 
 oval, and has a transverse diameter of from 0*03 to 0'027 mm. The 
 cirrhus of the ripe joint is usually directed to the opposite side from 
 that of the preceding, so that Tcenia echinococcus agrees with the other 
 cystic tape-worms in the irregularly alternating arrangement of the 
 generative openings. 
 
 Before this last ripe joint is liberated, a new joint appears; so 
 that for a while four proglottides are distinguishable, instead of three. 
 
 The calcareous corpuscles are somewhat large, and, in the more 
 transparent anterior part of the body, are easily found. In fresh 
 specimens the course of the vessels can usually be seen very beauti- 
 fully. Von Siebold even mentions the ciliation which is observable 
 in the anterior of the body-parenchyma, behind the suckers, at the 
 sides of the neck and body. 3 
 
 1 Von Siebold once saw a T. echinococcus with six suckers (loc. cit., p. 425). Nothing 
 was noted as to the structure of the segmented body. The fact that this malformation has 
 been seen only in one specimen is in favour of the opinion we previously expressed as to 
 its spontaneous origin. 
 
 2 My previous estimate (4000 to 5000) is too high. 
 
 8 Two memoirs, which have appeared while these sheets were passing through the 
 press, establish beyond cavil the repeatedly denied existence of a ciliary apparatus in the 
 
THE GENERATIVE ORGANS. 589 
 
 The Sexual Organs of Tcenia echinococcus exhibit many striking 
 peculiarities, which, when compared with those of other tape-worms, 
 contribute not a little to justify the independent position which we 
 have claimed for it here. 
 
 The Male Organs strike one by the unusual size of the cirrhus- 
 pouch, which measures almost 0'5 mm., and, by its club-shaped, 
 thickened posterior end, reaches to the middle line of the newly 
 fertilised joints. The cirrhus itself has apparently a greater indepen- 
 dence than is the case in the other cystic tape-worms. It lies in the 
 anterior portion of the cirrhus-pouch, like the glans in the prseputium, 
 and is not unfrequently protruded. Sometimes it is found in the act 
 of copulation. The sexual cloaca is destitute of a proper papilla, 
 the penis itself is bent into a sort of hook-shape, and is sunk into the 
 anterior end of the adjacent vagina. 
 
 Before its entrance into the posterior end of the cirrhus-pouch, the 
 vas deferens makes several irregular coils, which are mostly distended 
 with spermatozoa. In the testes, too, the spermatozoa are readily 
 recognisable since they possess an unusual length and thickness. 
 They are usually seen rolled up in curls, and can sometimes be observed 
 passing into the thin efferent canals of the testes. The size of the 
 testes is quite appreciable, averaging about 0*07 mm., and their number 
 is proportionately reduced to about sixty. 
 
 The Female Organs. The vagina is characterised by a longitudinal 
 enlargement (with a transverse diameter of 0'05 mm.) in the middle 
 of its course. In this there can be seen a yellow chitinous lamella, 
 with numerous points directed outwards. It is the same struc- 
 ture which we noted in the other cystic tape-worms. Its posterior 
 end leads to a distinct bladder (0*014 mm.), whose contents con- 
 
 vaacular system of Cestodes, and furnish also an almost exhaustive examination of the 
 latter system. The two memoirs are (1.) by Fraipont, " Rech. sur 1'appareil excreteur des 
 Trematodes et Cestoides," Archives de EioL, t. i., p. 415 ; and (2.) by Pintner, " Unter- 
 suchungen iiber den Bau des Bandwurmkorpers," Arb. des Zool. Instituts zu Wien, Bd. 
 iii., 1880. According to the harmonious results of both, the cilia are never found in the 
 course of the finer vessels, but only at their ends, and that in a sort of funnel-like enlarge- 
 ment, as was already known in part in regard to the Trematodes, having been demonstrated 
 by me in 1863 on the embryos of Distomum hepaticum (first German edition of this work, 
 Bd. i., p. 766). The funnels contain each only a single cilium, and this belongs to a cell 
 which shuts the mouth of the funnel like a lid, and was regarded by Pintner as a gland- 
 cell. The fine vessels pass out from the funnels, open without marked enlargement either 
 alone or in groups, and often after ramification, into the longitudinal vessels. The latter 
 never ramify, but are clad externally with an epithelium-like cellular coating, which has 
 probably a secretory character. Besides the existence of the ciliary apparatus, that of the 
 nervous system has been established by Pintner. The researches of this young investi- 
 gator refer primarily and principally to the Tetrarhynchi, which have less interest for us 
 here, although alluded to above (see p. 295) ; but there are many references to the 
 Taeniadae. The reports on the finer anatomy of the tape-worms are in beautiful harmony 
 with my results, though there are divergences here and there. 
 
590 
 
 DESCRIPTION OF THE ADULT T^IXIA ECHIXOCOCCUS. 
 
 sist of spermatozoa, in other words, into a receptaculum seminis. 
 
 Opposite the opening of the vagina there rises from this recep- 
 taculum a fertilising canal of 
 appreciable width, and distin- 
 guished by the double contour of 
 its walls. After a short course, 
 this divides into two narrower 
 ducts, of which the one bends for- 
 wards, while the other continues 
 the original course backwards. 
 The former of these two canals is 
 the oviduct whose upper end is 
 connected as usual with the two 
 ovaries. l The csecal tubules which 
 form the glands are short and 
 wide, and so slightly separated 
 that the ovaries look more like 
 lobulated sacs than aciniform 
 glands. Internally, the eggs may 
 be recognised as sharply defined 
 balls about 0*01 mm. in size. 
 The second canal divides further 
 down into two ducts one of 
 which enters the simple sacular 
 
 
 
 Flo. 318. Generative organs of Tcenia 
 tohinococcus. Male organs t.t., testea ; 
 c.p. , cirrhus-pouch ; c., cirrhus, curving round 
 to enter the vagina. Female organs ov., 
 ovary ; o.d. y oviduct ; r.., receptaculum 
 seminis ; y.j/., yolk-gland ; ut.. tube, pro- 
 bably leading to the uterus ; f.c., fertilising 
 canal ; v., vagina. ( x 80.) 
 
 yolk-gland, while the other is probably in connection with the uterus. 
 The latter appears from the first as a wide cavity. It is some- 
 what late before it is distinguishable, namely, after the ovaries 
 have liberated their contents, and, like the yolk-glands, have 
 disappeared. I have not been able to find a shell-gland in Tcenia 
 echinococcus. 
 
 Situation and Habits. This worm usually occurs in considerable 
 numbers, sometimes in many thousands, between the villi of the small 
 intestine, so that only the milk-white ripe proglottides project. 
 When the latter are not present, the worms can hardly be recognised 
 with the naked eye. 
 
 In the still warm intestine they exhibit lively and striking move- 
 ments. They elongate and shorten their joints, especially the first, 
 and move forwards in the surrounding intestinal mucus quickly and 
 powerfully, almost like leeches. Sometimes the body becomes so 
 thin that they almost resemble Kematodes. 
 
 1 The narrowness and general nature of the transverse efferent ducts of the ovaries 
 exclude the possibility (maintained by Sommer in regard to the other cystic tape- worms, 
 see p. 444) that they are glandular lobes. 
 
DURATION OF DEVELOPMENT AND OF LIFE. 591 
 
 According to v. Siebold's investigations, the metamorphosis of the 
 Echinococcus - heads into these tape -worms takes place with great 
 rapidity. Fifteen or twenty days after feeding he found on most of 
 the heads a two-jointed body, while others (the majority, according to 
 one of my experiments) were still without segmentation. 
 Thereafter three joints appeared, and some days later (on *-* 
 the twenty-seventh after feeding) some hard -shelled eggs ii 
 with embryos were found in the last joint. Van Beneden 
 also saw the J2chinococcus-\\esids becoming ripe Tcenice 
 within four weeks after feeding, while Kuchenmeister, Echinococcus 
 who experimented at the same time as v. Siebold, dis- k ef re . th e 
 
 r beginning of 
 
 covered no ripe forms for eight to nine weeks. In my ex- the segmen- 
 periments I did not find mature worms till the seventh tatlon ( x 15 )* 
 week. Zenker, even eleven weeks after feeding, found them perfectly 
 developed as regards size, but still without eggs. 1 In the feeding 
 experiments of Naunyn, Pagenstecher, and Nettleship, seven weeks 
 were also required for the attainment of maturity. 
 
 We do not know yet how long the tape- worm lives, but the insuffi- 
 ciently supported supposition of v. Siebold, that they did not survive 
 two months, can hardly be correct ; for not only does the form and 
 thickness of the roots of the hooks suggest in certain cases a greater 
 age, but we cannot suppose, against all analogy, that the productivity 
 of the worm is exhausted after the one or two proglottides. Further, 
 we must remember that the Tcenia echinococcus is, like the other cystic 
 tape-worms of the dog, found much more frequently in older animals 
 than in those still in the first year of their life. 
 
 Tcenia echinococcus was repeatedly observed before the researches 
 of the above-mentioned investigators. It was noticed apparently by 
 Eudolphi, who found it in immense numbers in a pug-dog. Its 
 attachment between the intestinal villi and its small size led, how- 
 ever, to the supposition that it was the young of the common tape- 
 worm of the dog (T. cucumerina), which had just arisen by generatio 
 sequivoca. 2 The villi were supposed to pass directly into tape- worms. 
 Later observers also considered these worms as young forms of other 
 species. Thus Eoll claimed them as young stages of T. serrata, and 
 Diesing was inclined to refer the specimens collected by Natterer 
 from a puma (Felis concolor) from Brazil to the large-hooked tape- 
 worms of the cat (T. crassicollis), and this, too, in spite of the expressly 
 noted ripeness of the last joint. Van Beneden in 1850 was the first 
 to recognise an independent species in this worm, which he described 
 
 1 Sitzungsb. d. med.-phys. Gesettsch. Erlangen, p. 88, 1872. 
 
 2 "Entozoor. hist, natur.," t. i., p. 411, 1808. 
 
592 DESCRIPTION OF THE ADULT TJ3NIA ECHINOCOCCUS. 
 
 as T. nana, 1 and, anticipating subsequent discovery, sought to refer it 
 to Echinococcus. 
 
 It is doubtful whether the worms collected by Natterer from 
 Felis concolor belonged to the same species as our native Echinococci. 
 It is, however, certain that our domestic cats are but little adapted 
 for rearing the T. echinococcus, as I have convinced myself by repeated 
 feeding experiments. I have also experimented in vain with rabbits. 
 Although v. Siebold remarks the same in regard to the fox, which 
 also belongs to the genus Canis, the dog is not by any means the only 
 host of T. echinococcus. We know, through the observations of Panceri, 
 that it occurs in the Egyptian jackal, and Cobbold notes that it is also 
 harboured by the wolf. 
 
 Of course T. echinococcus is not only observed in dogs which are 
 made the subjects of experiment, but occurs of itself spontaneously, 
 and in some districts not unfrequeutly. In Iceland Krabbe observed 
 it in 28 out of 100 dogs; in Denmark, on the other hand, 2 only twice 
 in 317, i.e., only 0'6 per cent. The conditions of life are nowhere 
 else so favourable as in Iceland, where the Echinococcus is almost of 
 common occurrence in men and cattle. 3 
 
 That the Echinococcus of man produces in the dog's intestine 
 the very same tape-worm as does the so-called E. veterinorum, 
 follows from the proof of the specific identity of these two formerly 
 distinguished forms. Nevertheless, the first feeding experiments (of 
 Kuchenmeister, Zenker, and Levison) yielded at first only a negative 
 result. The reason of this lay perhaps in the nature of the material 
 used, which, when obtained from the human corpse, is seldom so fresh 
 and well preserved as that from the ox, and partly also in the indi- 
 vidual conditions of the animals experimented on. For it does not 
 always happen, as v. Siebold has shown, that they are suited for the 
 rearing of the Tcenia from the Echinococcus. Later investigators have 
 been more fortunate. Thus Naunyn gave to two dogs the contents of 
 an Echinococcus from the liver, procured by tapping. One of them 
 exhibited, after thirty-five days, numerous Teenies, 3-5 mm. long, and 
 with eggs in their terminal joints. The other dog was examined eight 
 
 1 " Me'm. sur les vers intestin.," p. 158 : Paris, 1858. Kuchenmeister (" Parasiten," 
 second edition, p. 162, note) severely reproaches "the zoologist" v. Siebold, because in 
 1853 he did not know that T. echinococcus had been in 1850 described by " the zoologist " 
 van Beneden as T. nana ; but the reproach is as unjust as it is frivolous, since van 
 Beneden's memoir, presented in 1852 to the Paris Academy, was only published in 1858. 
 
 2 Similarly, in Giessen I only observed Echinococcus in the subjects of my experiments, 
 while from Gottingen the intestines of dogs infected with them were several times sent 
 to me. 
 
 3 [Thus it appeared formerly. I have recently learnt from Thomas (" Hydatid Dis- 
 ease," p. 191 : Adelaide, 1884) that in South Australia no less than 40 per cent. " of the 
 unregistered dogs " are infected by Tcenia echinococcus. R. L.] 
 
SUPPOSED OCCURRENCE OF THE T^NIA IN MAN. 593 
 
 days sooner, and was without Tcemce.* Krabbe also thrice obtained 
 a positive result in the experiments carried on by him and Finsen. 2 
 The animals used were all young and had lived under conditions 
 which excluded the possibility of a spontaneous infection, and were 
 seen on dissection to be free from T. marginata and T. ccenurus, which 
 so commonly occur beside the T. echinococcus in the Icelandic dog. In 
 five of the animals used no young Tcenice were to be seen, but this 
 negative result probably finds its explanation in the fact that the hy- 
 datids used for feeding were not always first examined to see if there 
 were heads present, and were further, in some cases, used several 
 days after the death of the host. The tape-worms found exhibited a 
 development and hook-formation corresponding to the period of feed- 
 ing, so that the cogency of the experiments can hardly be doubted 
 although they were made in Iceland in a country where T. echino- 
 coccus is extremely prevalent. 3 
 
 While Kiichenmeister still maintained the specific distinctness of 
 the human Echinococcus, and was forced, therefore, to regard the 
 Tcenia arising from the latter as different from the T. echinococcus, 
 he advanced the hypothesis that the tape- worm of the first occurred 
 not only in " dogs and cats," but specially in man himself, " in the 
 intestine of those individuals who suffer or have suffered from the 
 corresponding species of Echinococcus in any part of their body, and 
 in whom one of these Echinococci has opened into the intestine." 
 
 If this were indeed the case, then the existence of this Tcenia, 
 could hardly have escaped the investigations of the pathological ana- 
 tomists. In the new edition of his work on parasites, Davaine cites 
 no fewer than forty cases of Echinococci which had opened into the 
 intestine. In no case, however, was a T. echinococcus found, nor was 
 it so in any of the forty-five cases cited by the same author in which 
 the Echinococcus-bladdeYs opened into the bronchi, and in which their 
 contents had been coughed up. Kiichenmeister objects to the rele- 
 vancy of the question since the Echinococcus-heads did not reach the 
 stomach, but he forgets that the above conditions could hardly occur 
 without some portions of the Echinococcus being swallowed, and that it 
 is far more likely that the organism should be infected through forms 
 already in the mouth, than with forms that have first to be brought 
 into the mouth from outside. 
 
 Although Kiichenmeister does not regard my objection as valid, 
 and still keeps to his former opinion, in regarding man as well as the 
 
 1 "Ueber die zu Echinococcus hominis gehorige Taenia," Mutter's Archiv f. Anat. 
 u. Physiol., p. 412, 1863. 
 
 2 Loc. cit., pp. 49-52. 
 
 3 [Thomas refers to two feeding experiments with Echinococcus hominis, both of which 
 yielded positive results (op. cit., p. 205). R. L.] 
 
 2P 
 
594 
 
 DEVELOPMENT OF THE ECHIXOCOCCUS-BLADDER. 
 
 dog as the presumptive host of Tcenia echinococcus, yet we may all 
 the more readily leave the matter without further discussion since the 
 supposition in question is entirely hypothetical, and supported by 
 no facts whatsoever. We may confidently leave it to the future to 
 discover whether the T. echinococcus is found in the intestine of 
 Australian shepherds or of the inhabitants of any district where the 
 JZckinococcus-disesise is epidemic ; till then we must be contented with 
 the related bladder-worm stage. 
 
 I must take this opportunity of noting that, according to Leisering, 1 
 the Tcenia echinococcus, if occurring abundantly in the intestine of the 
 dog, sometimes occasions states which are in their external symptoms 
 so like hydrophobia that they could hardly be distinguished from it. 
 
 Development of the Echinococcus-Bladder. 
 
 Leuckart, Gottingen Nachrichten, Jan. 1862, or, in more detail, first German edition 
 of this work, p. 342. 
 
 Naunyn, " Entwickelung des Echinococcus," MuUcr't Archiv f. Anat. u. Physiol., p. 
 612, 1862. 
 
 The experiments made by Haubner and myself, in which we fed 
 lambs, sheep, and goats with ripe proglottides, remained without 
 result. The dissection was made sometimes soon, sometimes at a 
 longer time, after the feeding, but an Echinococcus was never found, 
 although we observed that the liver, and in many cases the lungs also, 
 were penetrated by small white points like miliary tubercles, which 
 could only be caused by the entrance of the young brood. 
 
 All the greater was my joy when I afterwards discovered that 
 the pig may be very readily infected by the eggs of Tccn'ia echinococcus. 
 
 The four experiments which I 
 made upon this animal were all 
 successful, and have enabled 
 me to establish a series of facts 
 which will always serve as the 
 starting-point for further ex- 
 periments. That I have not 
 traced to its close the life- 
 history of the Echinococcus, is 
 due to the fact that I have 
 of late lacked the necessary 
 materials. 
 
 In the first of my experi- 
 ments the young pig was examined four weeks after the feeding. 
 
 FIG. 320. Young Echinococcus, four weeks 
 old, escaping from the capsule. ( x 50.) 
 
 1 Bericht iiber das Veterindnvesen Sachsens, Jahrg. x., p. 87, 1867. 
 
STRUCTURE OF THE YOUNG ECHINOCOCCUS. 595 
 
 If developed at all, the young Ecliinococci ought, according to my 
 calculations, to have already measured several millimetres, but I 
 sought in vain in the liver, lungs, and other organs for any such 
 structures. The only phenomena which I could at all connect with 
 the experiment were some small knots resembling tubercles (perhaps 
 1 mm. in size), which shone through the serous covering of the liver 
 in various places. When on the point of concluding that I had again 
 experimented in vain, I discovered in the interior of these knots a 
 spherical body like a bubble, which, in spite of its insignificant size 
 (0'25-0*35 mm.), could be nothing else than a young Ecliinococcus. 
 
 When I first saw it, I almost believed it to be a mammalian egg. 
 A thick, homogeneous, and transparent capsule (0'02-0'05 mm. thick), 
 enclosed somewhat coarsely granular contents, 1 just as the zona pel- 
 lucida encloses the yolk granules. And just as the mammalian egg lies 
 embedded in the cells of the discus proligerus, the outer surface of 
 the clear capsule was surrounded by a substance, in which, upon 
 closer investigation, one could also discern a cellular texture. 
 
 Nothing suggested that it was an animal that lay before me. 
 Being motionless, and devoid of any trace of internal or external 
 organs, it would have been difficult to recognise it as a parasite, if the 
 circumstances under which it was found had not emphatically settled 
 the point. For the previous feeding, and the encapsulation of the 
 cysts, which in every respect corresponded to a Oz/s^'cemts-bladder, 
 placed the nature of the body beyond a doubt, especially since the 
 appearance and nature of the external envelope, in spite of the in- 
 distinctness of the lamination, recalled in- a very striking way the 
 cuticle of the adult Echinococcus. 
 
 The boundary of the outer wall appeared, as a rule, somewhat 
 sharply defined, but there were some, especially among the larger 
 specimens, in which the border was less distinct, as is also sometimes 
 the case with the zona of mammalian eggs. It was but slightly affected 
 by reagents, as though it already possessed the chemical nature 
 of the later bladder-wall. Its physical nature seemed also identical 
 with that of the later. It was extremely expansible and elastic, so 
 that the diameter of the bladder could be increased by pressure to more 
 than double. No structure could ever be observed in the " zona." 
 
 If left long in water the zona became separated here and there 
 
 1 Naunyn (loc. cit. ) describes in a similar manner the youngest Echinococcus found by 
 him in cattle. " They exhibited," he says, " a bladder of about ,V f a line in diameter, 
 whose wall already showed the structure characteristic of this bladder-worm. It was 
 comparatively thick, and displayed a tolerably distinct concentric lamination. The bladder 
 was tilled with small balls like tubercular granules, or with a fluid in which numerous fat- 
 drops were suspended. The latter appeared, however, to be due to a fatty degeneration 
 that had already set in." 
 
596 DEVELOPMENT OF THE ECHINOCOCCUS-BLADDER. 
 
 from the contents. It was then seen that the latter consisted, like 
 the yolk, of a clear granular matrix, which contained numerous fatty, 
 shining, coarser granules. The distribution of the latter was some- 
 what irregular, inasmuch as they were more numerous in the periphery 
 than in the interior. For the same reason, the central contents 
 appeared clearer than the peripheral ones, but this was the only point 
 in which they differed. The contents of the zona were thus still 
 perfectly solid, for no formation of fluid had yet set in. 
 
 The cells, which lay above the young Echinococcus, formed a thick 
 envelope, whose separate elements were so indistinctly defined that at 
 first sight it looked like a continuous granular substance. The size of 
 these cells was somewhat large, on an average about 0*027 mm. Each 
 of them contained a clear vesicular nucleus, from 0*007 mm. to 0*012 
 mm. in size, in which there were usually embedded two or three dis- 
 tinctly defined nucleoli. Sometimes I found cells with an oval or 
 elongated nucleus, or even with two nuclei, which were at a variable 
 distance from one or other. In the latter case the cellular mass was 
 usually constricted between the nuclei. There is thus no doubt that 
 the cells of this enveloping layer undergo active division, in exactly 
 the same way as I have observed in other bladder- worms, and especially 
 in those of the liver. 
 
 As to the connective-tissue cyst which enclosed the Echinococcus 
 and the enveloping substance, it was only of insignificant thickness, 
 and was everywhere in direct continuity 1 with the connective-tissue 
 trabecular network of the liver. We can hardly be wrong in sup- 
 posing that it originates principally from the latter by local develop- 
 ment and proliferation. In all cases, moreover, it was the interlobular 
 tissue that contained the parasites. The number of these amounted 
 to from four to six dozen, but none were found in any other situation. 
 
 If, however, any uncertainty had existed regarding the nature of the 
 bladder we have described, the case of the second pig, which was killed 
 four weeks later i.e., eight weeks after the feeding would have most 
 certainly removed it. The liver of this one was most certainly studded 
 with Echinococci, but they had in the meantime grown on an average 
 to double the size of the previous ones. Even with the naked eye 
 this increased size could be perceived, for the young Echinococci shone 
 through the enveloping walls like clear drops. 
 
 The cysts had of course also grown in proportion to, although 
 much less than, the parasites. Only in a few did the diameter exceed 
 1*5 mm., and that always in those whose inmates had also attained 
 
 1 According to Naunyn, a distinct connection can be proved between these cysts and 
 the wall of a vessel. " It thus appears," remarks this author, " as though the embryos of 
 Tcenia ecfiinococcus were distributed through the vascular system." 
 
LATER DEVELOPMENTAL STAGES. 
 
 597 
 
 more than the average size. As in the previous case, the cysts were ex- 
 clusively confined to the interlobular spaces, although their number was 
 much greater, and amounted to at least from 100 to 120. It is remark- 
 able that the cysts were all thickly distributed under the serous covering 
 of the liver, and that upon both the concave and convex surfaces. 
 
 The smaller Echinococci (of 0'5-0'8 mm.) corresponded in structure 
 with those found in the first experiment. The only difference per- 
 ceptible on superficial inspection was that the contents of the zona 
 were appreciably clearer than before. This increase of transparency 
 was due to a partial liquefaction of the contents. The Ecliinococcus, 
 which was formerly a solid mass, had meanwhile become a bladder, 
 which, when pricked, voided a portion of its contents in the form of a 
 transparent fluid, and then collapsed. 
 
 The fluid had collected in the centre of the spherical body, so that 
 below the zona a second membrane could be distinguished, which 
 lay along the inner surface of the latter, and is to be regarded as a 
 membranous expansion of the real body-parenchyma (" germinal mem- 
 brane," Huxley, " Keimhaut," Naunyn). The zona itself appeared as 
 a cuticle, and was distinctly lamellated, as we have already noted in 
 
 FIG. 321. Echinococcus-bl&dder eight weeks old. ( x 50.) 
 
 the adult ^cAmococcws-bladders. But the lamellse were as yet neither 
 very distinct nor sharply defined, although the membrane sometimes 
 attained a thickness of 0'07 mm. The inner membrane closely 
 adjoining the cuticle exhibited, besides the granules formerly pre- 
 sent, some cellular structures, which presented many differences in 
 
598 DEVELOPMENT OF THE ECHINOCOCCUS-BL ADDER. 
 
 size and appearance (sometimes measuring as much as 0'028 mm.). 
 Most of these were pale and delicately outlined, and to some extent 
 like drops, but there were others which were remarkable for the 
 granular nature of their contents, and there were even granular 
 cells of considerable size, not unlike pus corpuscles. In the larger 
 Echinococci the latter sometimes exhibited stellate ramifications and 
 a clear nucleus which shone through the granular substance. In 
 these large Echinococci (there were some specimens of from 2 to 2 -5 
 mm.) it was seen that the different kinds of cells exhibited a definite 
 arrangement. Most externally lay the small cells, and further inwards 
 the large drop-like bladders, while the granular cells were distributed 
 at irregular intervals over the surface. 
 
 I have not as yet succeeded in the attempt to observe the young 
 Echinococci in their earliest condition. A pig which was fed twice, at 
 intervals of five weeks, with a large number of ripe Tcenice, and was 
 killed fourteen days after the last feeding, only exhibited worms similar 
 to those which originated from the first feeding. 1 Some of them 
 measured as much as 3 mm., the others varied from 1 mm. upwards, 
 and even with the naked eye the above-described granular and radiate 
 cells could be seen shining through. What was both new and striking 
 to me was a thick border of granular spindle-cells, situated upon the 
 now distinctly laminated cuticle, from which they could only with 
 difficulty be separated. They agreed, however, with the adjoining 
 granular cells, except in the difference of their form. 
 
 Besides the structures just described, the liver of the animal con- 
 tained under the serous coating a number of small round or oval 
 cysts (of 0*3 to 0'8 mm.). These I at first also regarded as Echinococci, 
 especially since, like the latter, they belonged to the interlobular tissue, 
 but I discovered to my surprise that instead of a parasite they en- 
 closed a vegetable hair. This must have originated from the stomach, 
 whose walls it had perforated, and afterwards penetrated into the liver. 
 Apart from the analogy of this structure with the caterpillar-hairs 
 found encapsuled in the mesentery and liver of the frog, this view 
 was rendered more probable by the fact that the cysts were situated 
 almost without exception on the concave surface of the liver. The 
 comparison of these structures with the Echinococcm-cysts was of 
 interest, since not only were both bounded externally in the same 
 manner by a layer of connective tissue, but enclosed the very same 
 enveloping mass of granular cells. 
 
 1 In the same organs as the above-described young bladders, Naunyn repeatedly found 
 forms which perhaps represented the first stage of the bladder-worm. They were small 
 round structures about four times the size of an embryo, and were composed of granular 
 globules, and surrounded by a simple hyaline membrane. No embryonic hooks could be 
 perceived. 
 
STRUCTURE OF THE CUTICLE. 599 
 
 Having been convinced by previous experiments that the Echino- 
 coccus possessed a far slower development than other bladder-worms, 
 I determined to allow a longer time to a fourth animal, which had, 
 however, like the former ones, been used meanwhile in other experi- 
 ments (with Tcenia solium, T. marginata, and Trichina spiralis). The 
 examination was therefore not made until nineteen weeks after the 
 feeding. I hoped that after this lapse of time I should find the 
 Echinococci mature, and provided with heads ; but this time also my 
 hopes were doomed to disappointment. The experiment was certainly 
 successful, in so far as the liver (and it alone) contained between 
 thirty and forty bladders as large as nuts. On closer investigation 
 these proved to be Echinococci, but in spite of their size they were in 
 this case also still destitute of heads. Thus I had hitherto reared 
 mere acephalocysts, of exactly the same nature as those which Kuhn 
 has described with great accuracy in his above quoted monograph. 1 
 
 In this case also most of these young encysted worms lay close 
 under the serous covering of the liver, through which they shone more 
 or less distinctly. Some had pushed out the covering before them 
 into a lump, so that only the lower half was embedded in the 
 substance of the liver. The adjacent parenchyma was of normal 
 appearance, and not distinguished by abundance of blood, nor in any 
 other way. 
 
 All the more surprising was it that the capsular wall of the parasite 
 had in the meantime attained considerable thickness and firmness, 
 such as I had never observed in any other bladder-worms of the same 
 age. It was easily separable from the surrounding liver-substance, 
 and the outer layers also could easily be peeled off it. At the same 
 time its tension was so great that when cut it contracted powerfully, 
 and this rendered it extremely difficult to extract the parasite without 
 injuring its bladder. When this was successfully accomplished, 2 the 
 worm appeared in the form of a transparent bladder of fluid, either 
 round or nearly so ; that is, of course, when the bladder was suspended 
 in water. If placed on a firm surface it flattened out into a cushion- 
 like shape, proving that the surrounding membrane possessed only a 
 limited power of resistance. The average diameter amounted to some- 
 thing like 10 to 12 mm., but varied from 3 to 18 mm. 
 
 Here and there the otherwise transparent character of the bladder- 
 worm was dimmed by a thin white margin, which was situated on 
 the cuticle, and which, by the aid of the microscope, was recognisable 
 as a portion of the layer of cells enveloping the connective-tissue cyst. 
 
 1 M6m. soc. hist. nat. Strassb., t. i., 1830. 
 
 2 I recommend for this purpose dissecting under water a method which has enabled 
 me to extract Echinococci larger than the fist, uninjured from their capsules. 
 
600 DEVELOPMENT OF THE ECHINOCOCCUS-BLADDER. 
 
 On closer observation, it was also seen that the surface of the 
 Uchinococcus-l)\a,ddeT was not smooth, but broken by numerous fine 
 rents and cracks, which crossed each other and ran in different 
 directions. The same phenomenon was afterwards observed in other 
 Echinococci. It is as though the external layers, which are also the 
 oldest, no longer being able to resist the increasing pressure of the 
 growing mass, had ruptured. It is at least certain that the external 
 cuticular layers are much more tightly strained than the inner ones. 
 It is only necessary to cut the bladder at any point to get ocular 
 demonstration of this fact by the immediate rolling up of the 
 bladder-wall. 
 
 In bladders of about 1 cm. in diameter, on which our description 
 is based, the general thickness of the cuticle was about 0'2 mm. On 
 the internal surface the cuticle is more distinctly defined than on the 
 external, and is laminated throughout its whole thickness. As has 
 already been indicated, this lamination is obviously only the ex- 
 pression of a deposition in successive layers. While the external 
 layers are gradually destroyed, new ones are continually being formed 
 deep down, where the cuticle lies upon the parenchyma of the worm. 
 These are seen chiefly in the form of a distinctly marked border, 
 which extends along the boundary between the parenchyma and the 
 cuticle, and sometimes even remains visible when the former of these 
 is destroyed. The single layers of the cuticle are not, however, 
 always marked off from each other with equal distinctness, nor always 
 of the same thickness. As in the worms under consideration, the 
 latter may be estimated on an average at about 0*0035 mm. 
 
 The parenchyma which extends under the cuticle is, in spite of 
 its significance in the general life of the worm, of slight strength. It 
 hardly ever measures more than 0*12 mm., and on a side view in 
 fresh specimens is distinctly seen to be composed of two layers an 
 outer and an inner, as has already been mentioned in regard to the 
 larger Echinococci from the second experiment. 
 
 The vesicular structures directed towards the internal cavity ap- 
 peared, as in the Cysticerti, as rather sharply defined clear drops, 
 with a somewhat fatty lustre, and not at all unlike the so-called 
 " sarcode-drops." Most of them measured between 0*026 mm. and 
 0*036 mm., but there were some which were twice, or even three 
 times larger. In the external layer the elements had much more 
 emphatically the usual cellular character, although they were also 
 pale, and not very distinctly defined. Their size was markedly 
 smaller, being usually only about 0*07 mm., with the exception of the 
 granular cells, which measured about twice as much. Between the 
 cells there are found numerous coarse, strongly refracting grains, like 
 
ABSENCE OF AN EXCKETORY SYSTEM. 601 
 
 those above mentioned ; and also distinct calcareous corpuscles of 
 varying, and sometimes very considerable size. They are usually of 
 a lenticular form, and agree in appearance (lamination and apparent 
 formation of nuclei) with the corresponding structures of the related 
 worms, although they differ from them in becoming pale on the appli- 
 cation of acids, without evolution of gas. They are usually found 
 singly, and are distributed over the whole surface of the worm. 
 
 Since we noticed in the other bladder-worms that the appearance 
 of the first calcareous corpuscles was associated with the development 
 of the excretory vascular system, it might be supposed that the 
 EcJiinococcus also would be furnished with a similar apparatus. This 
 supposition seemed all the more probable from the fact that, according 
 to Naunyn's observation, the worms, even when of the size of a pea, 
 exhibited a lively ciliary motion. The cilia were sometimes placed 
 singly at some distance from each other, and at other times in groups 
 of five to ten. They were riot, however, situated on the parenchyma- 
 layer itself, but, strange to say, on its inner surface, so that they pro- 
 jected freely into the interior of the bladder. At first they were only 
 small, so that it was difficult to determine their form ; but afterwards it 
 was seen that at the lower end, by which they were attached to the 
 cellular layer, they were spherically thickened, and thus probably 
 always belonged to only one cell. 
 
 But in spite of this, neither Naunyn nor I have succeeded in 
 proving the presence of a vascular system in this parasite. It is true 
 that the cellular layer has, deep down, a peculiar system of net-like 
 anastomosing cords of more or less considerable thickness (as much as 
 0-008 mm.), but these cords do not give one the impression of vessels. 
 They appear rather to be solid bands of a homogeneous substance, 
 and are, as Naunyn says, similar to those which are seen by the 
 microscope on a glass smeared with fat or oil. 
 
 The ease with which they are destroyed renders the investigation 
 of these structures specially difficult. One needs only to expose the 
 worm or a short time to the influence of water or cold, or to press 
 the preparation roughly, to witness the immediate shrivelling up of 
 the former cords. Instead of the network, one finds in such cases 
 large round drops of a sarcodic nature. Similar results are produced 
 by the use of chromic acid and of Weissmann's solution of caustic 
 potash (36 per cent.). 
 
 Since the network is not a vascular apparatus, it might perhaps 
 be supposed to be contractile in function. But this interpretation is 
 also inadmissible ; not, however, because muscular fibres are altogether 
 absent from the EcJiinococcus, as was before erroneously supposed, but 
 because these muscular fibres, which one can hardly fail to see in the 
 
602 DEVELOPMENT OF THE ECHINOCOCCUS-BLADDER. 
 
 larger bladders after staining, had neither in nature nor arrangement 
 the slightest resemblance to that network. They appeared to be 
 longitudinally extended, thin, sharply defined fibrils (O001 mm. 
 thick), which crossed in different directions, never uniting so as to 
 form a closed layer or net, but always remaining separate, and at most 
 turning aside from their former course at the points where they divide. 
 
 Whether this peculiar network has any connection with the 
 ramified granular cells which I have already described in the larger 
 Uchinococcus-lAsiddeTS from my second experiment, or is perhaps even 
 formed from them, I must leave undecided, as also the question of its 
 physiological significance. In this connection I can only remark 
 that in one case, in which the still headless Echiiwcocci measured 
 from 12 to 20 mm., I sought in vain for the network, but again found 
 the previously observed cells with ramified processes, and noticed 
 that these were united here and there into real nets. It is true that 
 the appearance of the network in the two cases was very different, 
 and I must also own that the last-mentioned Echinococci were by no 
 means in so good a state of preservation as the former ones. Not 
 only was their parenchymal layer separated in some places from the 
 cuticle, but they were without the drop-like bladders, which, in other 
 specimens, lay upon the inner surface of the cellular layer, and in 
 some places they even exhibited distinct holes, wliich could be readily 
 observed on the cuticle. 
 
 When compared with the usual bladder- worms, the Echinococcus 
 consequently exhibits a whole series of unexpected peculiarities. It 
 is true that on the whole the analogy with the bladder of the Cysti- 
 cerci is unmistakeable, but, on the other hand, the immense thickness 
 of the cuticle, the absence of a powerful musculature, the slow growth, 
 and the late development, not only of the tape-worm head but of the 
 vascular system, and of the calcareous corpuscles (which, I may add, 
 are only found in specimens of at least 8 mm. in diameter), present 
 differences both numerous and important. Whether these peculiarities 
 are mutually dependent on each other, and whether they have any 
 connection with the thickness and firmness of the surrounding con- 
 nective-tissue capsule, or with the well-known peculiar structure of 
 the Echinococcus-hQ&d, we shall not further investigate. It is sufficient 
 to indicate generally the possibility of such a connection. 
 
 In conclusion, I may remark that, in spite of its thickness, the 
 cuticle of the Echinococcus possesses a very considerable capacity of 
 imbibition. If the extracted bladder be placed in water or spirits of 
 wine, it is observed that after a short time the parenchyma detaches 
 itself more and more extensively, and ultimately becomes a bladder, 
 suspended freely inside the cuticle, as has been depicted by Kuhn. 
 
STRUCTURE AND DEVELOPMENT OF THE ECHINOCOCCUS-HEADS. 603 
 
 If a coloured fluid be used, such as solution of carmine, the space 
 between the two bladders is immediately coloured, while the true 
 interior remains for a time clear. 
 
 Structure and Development of the Echinococcus-Heads. 
 
 Von Siebold, "Burdach's Physiologic," Bd. ii., p. 183, 1837. 
 
 Huxley, "Anatomy and Development of Echinococcus veterinorum, " Proc. Zool. Soc., 
 xx., p. 110, 1852. 
 
 Wagener, "Die Entwickelung der Cestoden," Nova Acta Acad. Cces. Leop.-Carol., 
 Bd. xxiv. Suppl., p. 34, 1854. 
 
 Naunyn, "Entwickelung des Echinococcus," MuLler's Archiv f. Anat. u. Physiol., 
 p. 612, 1862. 
 
 Rasmussen, "Bidrag til Kundskab om Echinococcernes Udvikling," Vid. Meddel. 
 not. Foren. Kjdbenliavn, p. 1, 1865. 
 
 The Echinococcus remains for a certain time in the condition which 
 we have described, but after perhaps five months, and when it has 
 become a bladder of 15 to 20 mm., it attains its full development by 
 the formation of the heads, which bud forth in ever-increasing 
 numbers from the parenchyma. 
 
 It is thus the presence of the head that characterises the adult 
 Echinococcus, and that not of a single one or of a few, but of many 
 thousands, all of which, so long as they live in their larval condition, 
 remain in connection with the bladder- wall from which they originate 
 and derive their nourishment. 
 
 In structure and mode of development these heads exhibit such 
 numerous and important divergences from those of the other cystic 
 bladder-worms, that it is necessary to examine them somewhat more 
 closely. 
 
 As has been already mentioned, the Echinococcus-'hQ^ in its adult 
 state consists of a solid mass of cylindrical form, in which, besides 
 the armed rostellum and the four suckers, there 
 is an egg-shaped posterior portion, which sometimes 
 passes by a broad base into the middle portion 
 bearing the suckers, or at other times is separated 
 from it by a constriction. The rounded end of this 
 posterior portion, in which we recognise the neck of 
 the future tape-worm, is furnished with a round 
 depression, destined for the reception of the muscular 
 stalk, by which the head is attached to its basis. 
 Even after the detachment of the stalk, the depres- 
 sion is, for a long time, distinctly visible. FlG 322. Head of 
 
 The length of the head (in its extended state) is Echinococcus veteri- 
 at most 0-3 mm., and about the half of this belongs norum ' ( x 90>) 
 to the posterior portion, which is usually distinguished from the 
 
604 STRUCTURE AND DEVELOPMENT OF THE ECHINOCOCCUS-HEADS. 
 
 anterior half by a more granular parenchyma (striated only in the 
 interior), and by a greater accumulation of calcareous corpuscles. 
 The calcareous corpuscles are somewhat large, or at any rate no 
 smaller than in the other cystic bladder-worms, but their numbers are 
 extremely variable in different specimens. On treatment with acids 
 they exhibit a brisk fermentation. 
 
 In favourable objects one can distinguish four coiled longitudinal 
 vessels, which unite in pairs before their entrance into the stalk, and 
 are connected below the circlet of hooks by means of a ring-like 
 anastomosis. Here and there are also some rapidly moving ciliated 
 lappets. Otherwise the parenchyma of the body is upon the whole but 
 little differentiated, and the musculature of the suckers in particular 
 is much less distinctly defined than is usually the case in other cystic 
 bladder-worms. 
 
 As to the hooks, it is well-known that they are distinguished from 
 those of the adult Tcenia (see Fig. 315) by the short and slender form 
 of their roots, especially in the case of the larger ones. It sometimes 
 appears as though the basal portion were wanting, as is indeed really 
 the case (p. 582). This imperfect development of the roots affects 
 the size of the hooks, as is shown by the fact that three linear 
 measurements taken from hooks of the first order amounted to 03, 
 0'015, and 0'014 mm. respectively, and three taken from those of the 
 second order 0'024, 0'013, and 0'014 mm. The first line extends from 
 the point of the hook to the end of the posterior root, the second from 
 the same point to the end of the anterior one, while the tliird indicates 
 the distance between the ends of the two roots. 
 
 In spite of the solid nature of the head, the anterior half, with the 
 circlet of hooks and suckers, may be entirely invaginated into the 
 posterior portion. In this state the head has an almost spherical 
 shape (018 mm.), like a Vorticella, with retracted 
 circlet of cilia. In the middle of its free anterior 
 border there is a more or less large depression, which 
 marks the place where the invagination has taken 
 place. Below this one sees the suckers, and further 
 down, in the neighbourhood of the stalk, the circlet 
 of hooks is observed shining through the paren- 
 chyma. The points of the hooks are, as a rule, 
 FIG. 323. Echino- directed upwards and outwards, so that, in its 
 the retracted state, the anterior part of the head has 
 head invaginated. ( x exactly the position and relation to the enclosing 
 posterior portion, which we saw the Cysticercus-lieaA 
 to bear to its so-called " caudal bladder." Nevertheless it is impossible 
 to regard the capsular envelope of the retracted JZckinococcus-head as 
 
OEIGIN OF THE HEADS IN BROOD-CAPSULES. 
 
 605 
 
 a caudal bladder, and that not only because it forms an integral 
 portion of the head, and is included in the body of the future tape- 
 worm, but more especially because of its entirely different origin. 
 
 Before proceeding to the discussion of these conditions I must 
 remind the reader that the earlier helminthologists believed the 
 heads to be placed directly upon the inner wall of the Echinococcus- 
 bladder. It was thought that they budded forth from this wall one 
 after another, and remained attached to it for some time after they 
 had completed their development. Even after the important dis- 
 covery of v. Siebold, that these heads were enclosed in small special 
 capsules situated upon the JZchinococcus-vf&ll, most zoologists remained 
 to some extent at least true to their former opinion, inasmuch as they 
 maintained that heads were formed and developed in two different 
 ways. Von Siebold, for example, taught that some only of the heads 
 originated in the interior of these capsules, and that others budded 
 forth freely from the wall in the form of little processes, which, from 
 the very first, were quite solid. 
 
 But further, it was even maintained, and indeed with the concur- 
 rence of all investigators, that the connection of the head with the 
 tissue whence it sprang was only 
 temporary. It was thought that after 
 their development (and eventually by 
 the rupture of the brood-capsules) 
 the heads detached themselves from 
 their origin, and, without losing their 
 vital powers, roamed about freely for 
 a long time in the fluid contained in 
 the bladder. 
 
 Unfortunately I am obliged to con- 
 tradict most of these assertions. 
 
 Not only do the JZchinococcus-'hesids originate, without exception, 
 within the brood-capsules, discovered by v. Siebold, but also in 
 their normal state these brood- capsules never rupture, nor allow the 
 contained heads to escape. According to my observations, all parts 
 of the Echinococcus (mother-bladder, brood-capsule, and head) are 
 throughout life in direct continuity with each other, as indeed I have 
 mentioned above. 
 
 I do not deny that one may often observe burst brood-capsules and 
 isolated heads, but I have only observed these conditions in encysted 
 worms, which were investigated some time after the death of their 
 host. If the worms were fresh, I found, without exception, the condi- 
 tions I have described : the heads all within their brood-capsules, and 
 all of these attached to the inner wall by means of a small stalk. 
 
 FIG. 324. Brood-capsule, with heads 
 of Echinococous in the interior. (x40.) 
 
606 STRUCTURE AND DEVELOPMENT OF THE ECHINOCOCCUS-HEADS. 
 
 But if the worm were exposed to the influence of external agents, or the 
 parenchyma brought into contact with water, or any other diffusible 
 fluid, the appearance altered, inasmuch as the brood-capsules burst, 
 and the heads contained in them became free. The latter were either 
 detached at once, or remained for a time in connection with the 
 shrivelled and rolled-up wall of the capsule, and were united in 
 groups, which were attached to the parenchymal layer by the stalk 
 of the capsule, irresistibly reminding the observer of a colony of 
 Vorticellce. 
 
 FIG. 325. Closed and ruptured brood-cappules, showing their connection with 
 the parenchymal layer, (x 40.) 
 
 There can be no doubt that it is these phenomena of incipient or 
 advanced maceration that have given rise to the numerous errors 
 regarding the structure of the Echinococcus, and the mode of develop- 
 ment of its heads, especially as the observations of Naunyn and Ras- 
 mussen have yielded results similar to my own. 1 
 
 Kegarding the genetic relations between the JZchinococcus-he&ds and 
 the brood-capsules, I must again differ from my predecessors. While 
 they assert that the heads originate on the inner surface, and that 
 they are from the first solid processes, I must, on the contrary, refer 
 their origin to the outer wall, and maintain that, exactly as in the 
 Cysticerci, the first rudiments of the heads are developed in the form 
 of hollow buds. 
 
 The buds situated on the outer wall of the brood- capsules had 
 already been occasionally observed, but they were generally mis- 
 taken, and regarded as adult heads, and on this ground many investi- 
 gators (including Huxley) maintain that the outer surface of the 
 brood-capsules is as well suited for the formation of heads as the inner. 
 
 The great susceptibility of the brood-capsules to the influence of 
 reagents is explained by the thinness of their membrane, which even 
 
 1 I must not, however, omit to mention that Klebs (" Handbuch der pathol. Anat.," 
 Bd. ii., p. 586) has lately reported that in the human Eckinococcus he has several times 
 found isolated heads situated directly upon the parenchyma. Frerichs and Sommerbrodt 
 are also said to have observed similar cases, 
 
STRUCTURE OF THE HEAD. 607 
 
 in the larger capsules hardly measures more than 0*004 mm. But in 
 spite of this thinness the capsular membrane exhibits a distinct 
 histological differentiation. In the interior may be perceived a 
 delicate, sharply defined cuticle, which lines the cavity, and on the 
 outside a thin layer of clear granular cells, which correspond to the 
 superficial cell-elements of the true parenchyma of the JSchinococcus, 
 and differ little from it historically. At the point of insertion of 
 the head one can often distinguish a pair of vessels, which run thence 
 into the capsular membrane. They anastomose freely with the vessels 
 of the adjacent heads, and sometimes unite in the neighbourhood of 
 the stalk of the brood-capsule into a true network, the offshoots of 
 which are seen passing through the stalk to the parenchymal layer 
 of the bladder-worm. In the latter they soon disappear from sight. 
 At most, one can only follow them into the vessels of the stalk of an 
 adjoining brood-capsule, with which they unite. On the Echinococcus- 
 bladder itself, the vessels, if present at all, are much less distinctly 
 marked than is the case in other bladder-worms. 
 
 I have never been able to find muscular fibres in the brood- 
 capsules, although they not unfrequently exhibit a powerful peristaltic ! 
 motion, which as a rule originates from the point of attachment. The 
 drop-like bodies which lie on the inner surface of the cellular layer 
 of the parenchyma are also wanting ; but, in spite of this, I have no 
 hesitation in regarding the brood-capsules as a local development of 
 the bladder-wall. Since the separate layers have an exactly opposite 
 position to those of the bladder- wall, they may be regarded in some 
 respects as an invagination of the latter, just as we previously assumed 
 (p. 357) when seeking to establish the morphological relation of the 
 Echinococcus to the other bladder-worms. 
 
 As to the structure of the head itself, it is essentially the same as 
 the head-process in the Cysticercus. First of all a discoidal thickening 
 originates in the wall of the brood-capsule, which quickly rises and 
 grows into a club-shaped process, whose longitudinal axis is perforated 
 by a canal-like continuation of the interior of the brood-capsule. 
 Like the cavity of the latter, the canal has on its inner surface a 
 cuticle, and that a firmer one than was found there. Similarly, in 
 spite of the resemblance in histological structure, the wall of the 
 process is much thicker than that of the capsule. 
 
 Although composed only of cells, the rudimentary head has now a 
 striking contractility. It stretches out, and may then contract to per- 
 haps half its former length ; it curves and swings like a pendulum to 
 right and left, or may even be invaginated into the brood-capsule, so 
 that the cuticle then becomes an outer coating, as in the Echinococcus- 
 heads. This invagination sometimes occurs at an early stage, before 
 
608 STRUCTURE AND DEVELOPMENT OF THE ECHINOCOCCUS-HEADS. 
 
 the rudimentary head has grown to any considerable size. Since one 
 sometimes sees beside such small invaginated buds others which 
 represent a later developmental stage, it often appears as though the 
 Echinococcus-lieSids budded off as a whole inside the brood-capsule, 
 and were developed from the first in their subsequent position with 
 the cuticle outwards. At first a simple cylindrical process, the bud 
 gradually assumes a club-like or pyriform shape, becoming constricted 
 at its basal end. Afterwards it becomes modified by the formation 
 of the hooks round about the free rounded end, where the border 
 projects in a sort of circular fashion. Further back, at the bulging 
 portion of the bud, the first traces of the suckers begin to appear 
 (Fig. 327). 
 
 FIG. 326. Brood-capsule of Echinococcut FIG. 327. Development of the 
 
 vetcrinorum, with adult and hollow rudi- Echinococcus-heads from those hanging 
 
 mentary heads. ( x 40. ) freely into the internal cavity of the 
 
 brood-capsule (after Wagener). ( x 90.) 
 
 The rudimentary hooks appear first in the form of a somewhat 
 thick fringe of prickles, which surround the cephalic end like a girdle, 
 but which afterwards all disappear except the foremost rows, which 
 have grown gradually stronger. When the circlet of hooks has almost 
 attained its subsequent structure, it is retracted along with the 
 adjacent sucker-bearing portion, and sinks into the gradually enlarg- 
 ing posterior portion of the body. The internal cavity of the bud, 
 which has not been lost by the invagination, then becomes obliterated, 
 and the histological differentiation progresses, producing muscle-fibres, 
 vessels, and calcareous corpuscles; and after constriction and the 
 formation of a stalk at the point of insertion, the head lias attained 
 its final form. 
 
 I will not deny that the development of the Echinococcus-lieads 
 sometimes takes place in the way thus described (after Wagener). I 
 have indeed sometimes observed Echinococci in which the rudi- 
 mentary heads almost all projected into the brood-capsules, and 
 exhibited the above developmental stages in uninterrupted succes- 
 sion. But I must most emphatically deny that the development 
 of the heads in the above-described position is the only mode. Beside 
 
MODE OF DEVELOPMENT OF THE HEADS. 609 
 
 the buds freely projecting inwards, one always finds others, and 
 occasionally the majority, in which the head-rudiments hang from 
 the brood -capsules into the common bladder-cavity, just like the 
 head-processes of the Cysticerci. They undergo a metamorphosis just 
 like the latter, and differ only in the fact that there is never a recep- 
 tacular sac in which the head is bent together. 
 
 The analogy here referred to corroborates my opinion that the* 
 exogenous development of hollow buds is the typical mode of origin 
 for the Echinococcus-he&ds, while the previously described endogenous 
 mode, even if as frequent as Naunyn 1 and Kasmussen assert, is in 
 reality exceptional. At any rate, these two observers agree in this 
 and this is the main point that both modes of development occur in 
 the Echinococci. 
 
 When the Ecliinococcus is developed, in the way last described, to 
 that stage in which the histological differentiation begins, then its 
 former attitude changes, and it becomes invaginated from the point of 
 insertion into the internal cavity of the brood-capsule. What took 
 place in the first mode at an earlier stage here occurs at a later 
 stage, with the further difference that the invagination is usually 
 restricted to the posterior (basal) half of the head. The inception 
 of the hooked apparatus and of the suckers in such cases is thus 
 no secondary state, but an occurrence which arises in the original 
 formation, and is therefore to be regarded as typical. When the 
 invagination of the basal half has taken place, then, as we have 
 formerly described, the now contiguous walls of the hollow bud fuse 
 with one another. The head solidifies and constricts at its point of 
 insertion; in other words, it assumes the appearance of the endo- 
 genously developed head. 
 
 The older the brood-capsule becomes, the more does the number of 
 the inmates increase, so that I have sometimes counted twelve to 
 fifteen, and Eschricht twenty-two. Even in such populous capsules 
 one often sees another new crop of buds (often three or four) at 
 different stages of development. But not only do the heads of the 
 Echinococcus gradually increase, but the number of the brood-capsules 
 likewise, so that the larger and older worms sometimes contain many 
 thousands. 
 
 1 Naunyn notes (loc. cit., p. 621, note) that in those Echinococcus -bladders which were 
 warmed to about 35 C. before being opened, the buds were almost always found inside the 
 brood -capsules, while in the same, after cooling, the buds were very frequently found on the 
 outer surface. This would seem to show that the buds can be invaginated or evaginated 
 according to circumstances that the invagination is, in other words, by no means perma- 
 nent. But this would, I think, also hold good on my theory ; for why should the buds 
 have the power of evagination and an internal cavity, if they develop from first inside the 
 brood-capsule ? 
 
 2 Q 
 
610 STRUCTURE AND DEVELOPMENT OF THE ECHINOCOCCUS-HEADS. 
 
 The formation and multiplication of these capsules takes place, 
 according to my observations (confirmed by Naunyn), as follows : 
 
 At distinct points on the parenchyma one notices at first small, 
 wart-like elevations. These are proliferations of the cellular layer, 
 which are even already (according to Naunyn) possessed of a number 
 of actively vibrating cilia, which are still distinct at a later stage 
 even after the formation of the head. When the elevations have 
 grown to about double the thickness of the wall from which they 
 spring, one can recognise inside them a small spheroidal cavity, which 
 is very soon clad with a delicate cuticular membrane. Process and 
 cavity then grow to perhaps three or four times their original diameter. 
 The cellular layer, which had at first a considerable thickness, becomes 
 thin, and forms at some point or other, usually opposite the point of 
 insertion the first hollow bud which, sometimes as an external 
 appendage ((7), and sometimes inwardly invaginated (Z>), becomes the 
 first head, which is soon succeeded by others. 
 
 Fio. 328. Development of brood-capsules (A) and of the appended 
 heads. (B\ first rudiment of the head ; (6'), further development j (Z>), 
 invagination ; (), subsequent budding. ( x 90. ) 
 
 With the number of the budding heads the size of the brood- 
 capsule also increases proportionally, so that many attain a diameter 
 of 1*5 mm. Such large brood- capsules contain here and there per- 
 haps a dead head, which is separated from its germinal layer, and 
 is readily distinguished, by its shrivelled form and brownish colour, 
 from the living and active, though but slightly mobile, heads. 
 
 It seems further as though the power of forming such brood- 
 capsules were usually confined to certain portions of the Echinococcus- 
 bladder, and never uniformly distributed over the whole inner surface. 
 This is what we find in the Cwnurus, where the heads are budded off 
 in groups here and there at varying distances apart. 
 
 There is considerable diversity as to the size which an Echinococcus- 
 bladder must attain before it produces brood-capsules and heads. 
 Usually this process may begin when the bladder has become as large 
 
FORMATION OF DAUGHTER-BLADDERS. 611 
 
 as a big hazel-nut. Under some circumstances it is postponed to a 
 still later stage. In a cow which. I examined, where lungs and liver 
 were penetrated with perhaps 150 Echinococci, there were, besides the 
 usual bladders thickly beset with brood-capsules, others which were 
 still barren, although they had attained the size of a hen's egg, while 
 in others, with a diameter of 10 mm., the formation of heads had 
 already begun. In the so-called " Echinococcus multilocularis" the 
 heads were sometimes found in bladders with a diameter of less 
 than 1 mm. 
 
 We do not know how these differences are conditioned, nor how 
 it comes about that certain Echinococci (the acephalocysts) never form 
 brood-capsules or heads at all. One may indeed suppose that the 
 nature of the parenchymal sheath is a determinant factor, but what the 
 special peculiarities are is as yet unknown, and will probably remain 
 unknown for long, owing to the difficulties which beset a thorough 
 histological analysis of the bladder-wall. 1 This is also true in regard 
 to the causes of sterility, 2 though disturbances of nutrition are pro- 
 bably largely influential in this connection. 
 
 The Formation of Daughter -Bladders and the different Forms of 
 the Echinococcus. 
 
 Kuhn, " Recherches sur les Ac6phalocystes : " Strassbourg, 1832. 
 
 Naunyn, " Entwickelung des Echinococcus," Mutter's Archiv f. Anat. u. Pkysiol., 
 p. 612, 1862. 
 
 Rasmussen, "Bidrag til Kundskab om Echinococcernes Udvikling," Vid. Meddel. 
 not. Foren. Kjobenhavn, p. 1, 1865. 
 
 With the above-described changes, the Tcenia echinococcus has 
 completed the bladder-worm stage of its development. The originally 
 very small, six-hooked embryo has grown into a large bladder, which 
 is beset internally with brood-capsules, which again produce an 
 immense number of tape-worm heads. 
 
 What distinguishes the Echinococcus from other bladder- worms is 
 not so much the great number of these heads, as the appearance of 
 special brood-capsules, whose structure and development proves them 
 to be structures as distinct as the bladder and head. They are related 
 to the bladder, as the twigs of a tree are to the stem from which 
 
 1 These difficulties explain the numerous erroneous hypotheses which interpret the 
 parenchyma sheath even as a fat deposit, a simple epithelium, &c. But we need not 
 point out that such views are inconsistent with any appreciation of the physiological 
 importance of this layer, which represents neither more nor less than the whole of the 
 active organic apparatus of the Echinococcus. 
 
 2 Helm, " Ueber die Productivity und Sterilitat der Echinococcusblasen," Archiv f. 
 pathol. Anat., Bd. Ixxix., p. 141, 1880. 
 
612 VARIOUS FORMS OF ECHINOCOCCUS. 
 
 they bud forth. But as the twigs are morphologically nothing more 
 than repetitions of the stem from which they spring, so are the brood- 
 capsules, in a certain sense, nothing more than repetitions of the 
 bladder which bears them. They are daughter-bladders, individually 
 developed members of the Echinococcus, through whose budding the 
 originally simple bladder-worm forms a colony. Although morpho- 
 logically equivalent to the mother-bladder, they attain only an imper- 
 fect physiological individuality, as is so frequently the case in colonies. 
 They remain connected with their mother-bladder, and undertake for 
 the latter, according to the law of the division of labour, the function 
 of head-formation. This specific function accounts for the differences 
 which we have seen to obtain anatomically between the brood-capsules 
 and the mother-bladders, and which essentially consists in the inverted 
 order of the cuticle and the parenchymal sheath. 
 
 In many cases, especially in the Echinococcus of cattle (E. veteri- 
 norum), the worm remains in the above state till its host dies, or till 
 the heads find an opportunity of becoming Tcenice (p. 591). The 
 only change, apart from the multiplication of brood -capsules and 
 heads, consists in a continued, though perhaps but slow, growth of the 
 bladder. We know, however, instances in which the Echinococcus 
 (and that the simple form) has grown so as to attain a diameter of 
 15 cm. As a rule, indeed, the worm in this form attains but a 
 comparatively small size hardly greater than that of a fist or 
 an orange. 
 
 In this increase in size the cuticle also participates, and that to a 
 much greater and more striking extent than the parenchymal sheath. 
 It becomes thicker the more the bladder-body grows, and in many 
 cases measures as much as 1 mm. or more. The lamellar stratification 
 remains as before, except that the lamellae become more sharply 
 defined, and increase in thickness. Nor does the elasticity of the 
 cuticle experience any diminution: it seems in the large bladders 
 hardly less conspicuous than in the small ones. One only needs to 
 touch them to see how the tremulous motion spreads over the whole 
 mass. This is not only perceptible to sight and feeling, but even to 
 hearing, so that, after the example of Brian^on and Piorry, the so-called 
 " hydatid tremor " and rustling obtained on percussion have been used 
 as a corroboratory diagnostic test. 1 
 
 As the cuticle thickens, so does the connective-tissue cyst sur- 
 rounding the worm. It becomes a sac, the wall of which often measures 
 
 1 See on this point besides Piorry, "De la percussion mediate," p. 153, Paris, 1828, 
 and especially Davaine, Gazette mtd., No. 20, 1862. Kiichenmeister maintained for some 
 time the erroneous opinion that this rustling noise was audible only in the hydatid form 
 of Echinococcus. 
 
THE SIMPLE FORM OF ECHINOCOCCUS. 613 
 
 5 mm., or even double that, and acquires a quite extraordinary firm- 
 ness. It possesses its own arteries and veins, which spring from the 
 neighbouring vessels, and are connected by a rich capillary network. 
 On the smooth internal surface it bears at first a thin layer, which is 
 fastened almost as firmly to the Jc^m0c0cczS-membrane as to the 
 surrounding wall of the cyst, and which, on microscopic investigation, 
 is seen to be the cellular deposit already repeatedly mentioned. 
 
 As to the form of the Echinococcus, it is usually spherical (Fig. 317), 
 but there are also bladders which possess an oval form, or by unequal 
 development of the surface have become more or less bulging, as is to 
 be seen in the adjoining representation. As a rule, such irregular 
 forms find their explanation in the character of the connective-tissue 
 cyst and its surroundings. They arise when the growing bladder 
 encounters obstacles of varying strength. 
 
 FIG. 329. Bulging Echinococcus in its natural size and position. 
 
 The fluid which fills the internal cavity of the JZchinococcus-bl&ddeY 
 has commonly a clear watery character. It is not coagulated either 
 by boiling or by application of acids, and has in its fresh state no 
 corpuscular contents. The brood-capsules and fichinococcus-he&ds, 
 which the older observers saw swimming freely in this fluid, are in 
 fresh specimens all attached to the internal surface. They shine 
 through the body-parenchyma, which is usually transparent, though 
 occasionally turbid at isolated spots, or even throughout. 
 
 The brood-capsules produced by these EcJiinococci have been 
 already claimed as daughter-bladders, and, indeed, proliferating 
 daughter-bladders. But they do not represent the only form of 
 daughter-bladder which these worms can produce. Beside these, 
 there not unfrequently appear other daughter-bladders, which possess 
 exactly the structure and nature of an ordinary Echinococcus, yet do 
 
614 VARIOUS FORMS OF ECHINOCOCCUS. 
 
 not come to lie inside the bladder space, but are fixed on externally, 
 as Kuhn long ago described in the case of his acephalocysts. 1 
 
 In my earlier investigations I often saw this process of proliferation 
 in cases of multiple Echinococci, and am still prepared to maintain the 
 correctness of the observations. Naunyn has indeed urged a theoretical 
 objection, which seems to me, however, as though directed rather 
 against the form of my representation than against the actual facts. 2 
 
 But before I enter into a discussion of the question, I must again 
 expressly note that not all Echitwcocci, even in the above cases, 
 exhibit this process, but only a few generally those which are of a 
 medium calibre. But since, as a rule, several daughter-bladders are 
 thus formed at once, these are often found seated on the mother-bladder 
 in groups attaining about the size of a pea. 
 
 FIG. 330. Proliferation of the membrane of an Echinococcus (nat. size). 
 
 The formation of daughter-bladders does not proceed directly from 
 the external surface, but begins in the thick cuticle, and indeed in its 
 deeper layers. At a definite point we notice at first, between the two 
 lamellae, a little heap of granular substance which presses the adjacent 
 layers apart, and after some time becomes surrounded by a special 
 cuticle. By repeated excretion of cuticular layers the granular heap 
 becomes the centre of a special system of ever-increasing lamellae. 
 
 It is not, however, only the formation of new envelopes which 
 determines the growth of the embedded body, but also the increase in 
 the mass of the contents, which gradually lose their former appearance, 
 clear up, and pass through the changes which have been already 
 described in treating of the development of the primary Echinococcus- 
 bladders. At a certain developmental stage one finds the same stellate 
 
 1 Megnin has lately observed a very remarkable case of this kind ("Sur une nouv. 
 forme de ver vesicul.," Jaurn. de TAnat. et de la Physiol., p. 6, 1880). This was an 
 Echinococcus which was developed in the leg of a horse, and had to a large extent 
 penetrated and displaced its muscles. The Echinococcus of the upper part of the leg 
 observed by Kanzow, and more closely examined by Virchow (Archiv f. patkol. Anat. t 
 Bd. xxix., p. 180), ought also to be noted. 
 
 2 On the other hand, my observation has been confirmed by Pagenstecher ( Vcrhandl. 
 nat.-med. Vereins, Heidelberg, Bd. i., p. 5), and Rasmussen (loc. cit.), I have since 
 observed that in 1857 Levison made the same observations (" Disquis. nonn. de Echino- 
 coccis," Dissert, inaug. Gryphiae). 
 
INTERLAMELLAR FORMATION OF THE DAUGHTER-BLADDERS. 615 
 
 granular cells which we formerly noted. There can hardly be any 
 doubt, then, that these embedded bodies are rightly regarded as 
 daughter-bladders. 
 
 They gradually emerge of course from the deeper parts of the 
 cuticle, since new cuticular layers are always arising internally, as 
 those outside (p. 600) gradually disappear. The superjacent layer of 
 the cuticle of the mother-bladder becomes pushed forward as a sort of 
 hernia. The more the daughter-cell grows, the more accentuated does 
 the protrusion become, until it finally bursts and sets free its inmate. 
 In many cases the daughter-bladder becomes abortive soon after its 
 isolation (perhaps under the pressure of the surrounding wall of the 
 cyst), but in other cases it develops beside the mother-bladder. It is 
 at first enclosed in a lateral pouch of the original cyst, but in the 
 course of time it usually acquires an independent envelope, a partition 
 wall gradually growing up in the space intermediate between the 
 mother and daughter-bladder. In the last stage it is of course hardly 
 possible to distinguish the secondary JZchinococcus-loladdeYS arising by 
 proliferation from the primary parasite, which originated from the 
 metamorphosis of a six-hooked embryo. A valid difference, however, 
 seems to me to lie in the fact that the daughter-bladders are able to 
 produce brood-capsules sooner than their mothers. 1 
 
 The objections which Naunyn urges against my observations have 
 to do less with the real facts for he himself admits having seen 
 peripheral daughter-bladders than with my assertion that they arise 
 " independently of the parenchymal layer of the mother." In this 
 expression I have, indeed, affirmed too much, more, in fact, than 
 I intended. At first I only wished to indicate that the daughter- 
 bladders have an independent development, and exhibit no permanent 
 connection with the parenchyma of the mother. As to the nature of 
 the granular mass which furnishes the point of origin of the daughter- 
 bladder, no additional light has been cast upon it by my observations, 
 but I have no scruple in deducing it from the parenchymal layer of 
 the mother. It obviously represents a portion of the latter, a bud-like 
 outgrowth, so to speak, which separates itself from the matrix, 2 and 
 becomes ever further separated from it by the subsequently formed 
 cuticular layers. In agreement with this is the fact that the daughter- 
 bladders, so long as they are small, lie in the deeper layers of the 
 cuticle, and only gradually work their way outwards. 
 
 1 Morin observed the formation of heads (in a case of Echinococcus multllocularis) in 
 the daughter-bladders, although none of them had become separated (" Deux cas de tumeurs 
 a echinococquesmultiloc.," Dissert, inaug. Lausanne, p. 32, 1876). 
 
 2 Naunyn sometimes saw (loc. cit., p. 631) a very fine canal running through the sub- 
 jacent layers of such a peripheral daughter-bladder, and even opening into the latter, so 
 that it looks as though this separation were sometimes delayed to a later period. 
 
616 VARIOUS FORMS OF ECHINOCOCCUS. 
 
 The form of Echinococcus whose proliferation I have here described 
 is that which Kiichenmeister formerly maintained to be the repre- 
 sentative of a distinct species E. scolecipariens. The name is not 
 very distinctive, since the other forms of Echinococcus also produce 
 scoleces. It might have been more appositely called E. granulosus or 
 simplex, if one do not prefer Kuhn's designation of " exogenous " 
 Echinococcus. After our previous discussion, we need not repeat that 
 it does not represent any distinct species. 
 
 This simple Echinococcus is specially frequent in domestic 
 mammals, particularly in the pig, which, in this country, is the 
 animal most infested with Echinococcus. But even in man it is not 
 a rarity. Kiichenmeister, in the first edition of his "Parasiten," 
 recounts, it is true, only two cases one observed by Gescheid 
 (Echinococcus of the eye), and another by Eschricht (Echinococcus in 
 the liver, from Iceland, usually compound) ; but a very superficial 
 review of the numerous cases of Echinococcus now reported is sufficient 
 greatly to increase the number. x The case of Eschricht is further of 
 importance, inasmuch as he was one of the first expressly to mention 
 the head in the simple Echinococcus occurring in man. 
 
 Generally the Echinococcus granulosus occurs in the omentum under 
 the peritoneal covering of the abdominal wall and in the bones, but 
 there are also instances of its occurrence in other organs, especially 
 the liver, spleen, lungs, which attract our attention all the more 
 readily since the worm in these places usually grows to a considerable 
 size. We must, therefore, note expressly that the simple Echinococcus 
 is not the only form which the above organs harbour ; indeed, another 
 form is very frequently found, which is characterised by the possession 
 of daughter-bladders internally. In the lungs and liver this com- 
 pound Echinococc-iis is actually much more frequent than is the simple 
 one, which does not, of course, exclude the possibility of their occa- 
 sional occurrence together in the same body, and often close beside 
 one another. 2 
 
 This second compound form of Echinococcus is that which Kiichen- 
 meister designated E. altricipariens, a name which has now fallen into 
 disuse, and may very suitably be replaced by the name E. hydatidosus 
 (Echinococcus endogena of Kuhn). 
 
 This Echinococcus hydatidosus is distinguished from the above- 
 
 1 Somraerbrodt, who has collected the cases of E. granulosus occurring in man 
 (Archiv f. pathol. Anat., Bd. xxxvi., p. 272), estimates them at seventeen, but this 
 number has been tripled by Becker, Neisser, and Helm. 
 
 8 Specially instructive is a case observed by Haen (quoted by Davaine, loc. cit., p. 
 367), where simple and hydatiform -fic&inococeus-bladders occurred in the liver of the same 
 individual. Similar cases are also reported by Wunderlich (Archiv f. physiol. Heilkunde, 
 p. 283, 1858), by Davaine (Mtm. Soc. biol., p. 106, 1857), and by Helm (loc. cit., p. 148). 
 
FERTILITY AND STERILITY OF ECHINOCOCCUS HYDATIDOSUS. 617 
 
 described simple E. granulosus, not exactly by the presence of 
 daughter-bladders for these may be produced also by the latter 
 but by the presence of daughter-bladders in the interior of the mother- 
 bladder, structures which are not only found often in large numbers, 
 but which may grow to an appreciable volume, and sometimes them- 
 selves produce daughter-bladders. Further, the large size which the 
 hydatidose Echinococcus usually attains is also noteworthy ; cases are 
 known in which it weighed from 10 to 15 kilogrammes, and therefore 
 far exceeded the largest E. granulosus. 
 
 I cannot conceal that, among the almost countless cases of E. 
 hydatidosus reported in medical literature, there are many in which 
 no mention is made of the mother-bladder, so that the bladders 
 (hydatids) lay apparently immediately in the surrounding connective- 
 tissue cyst, and were in fact to be regarded as daughter-bladders in 
 the same sense as those of E. granulosus. This silence does not, of 
 course, warrant us in inferring the actual absence of the common 
 mother-bladder not only because the descriptions often suggest that 
 the mother-bladder was attached to the enveloping connective-tissue 
 cyst, and was considered to be an integral part of the latter, but 
 also because it not unfrequently happens in the course of time that 
 the mother-bladder is destroyed by the continually increasing number 
 of daughter-bladders. Bocker and Helm recount a whole series of 
 cases in which the mother-bladder had either degenerated or been 
 torn, and here and there the membranous remains were still found in 
 the pulpy mass enveloping the daughter-bladders. 
 
 In regard further to the co-existence of daughter-bladders and 
 heads, the above reports must be received with caution. This is 
 especially true of the oft-repeated assertion that E. hydatidosus is 
 devoid of heads an assertion which was explained by Davaine, who 
 supposed that the formation of the daughter-bladders preceded by some 
 time the formation of heads. 1 The commonly asserted absence of 
 heads shows only that the observers failed to find them. And this 
 may all the more readily occur, since the daughter-bladders of the 
 hydatidose Echinococcus are, in point of fact, often sterile. I had to 
 examine many daughter-bladders before I found those with brood- 
 capsules and heads. Other investigators, such as Lebert and Helm, 
 have had a similar experience. On the other hand, there are 
 hydatidose Echinococci whose bladders all bear heads. Thus Eschricht 
 reports that in one of his cases all the daughter-bladders, some thirty 
 in number, both large and small, from the size of a hen's egg to that 
 of a pea, contained brood-capsules and heads. Helm similarly reports 
 
 1 "Rech. sur les hydatides, les 6chinococques et le coenurus," M4m. Soc. liol., 1855 ; 
 Gaz. Mid., 1852. 
 
618 VARIOUS FORMS OF ECHINOCOCCUS. 
 
 that in many cases he found the mother-bladder beset with brood- 
 capsules and heads sometimes by itself, and sometimes along with the 
 daughter-bladders. Where the proliferating and sterile bladders occur 
 together, the former are sometimes (Levison, Helm) characterised by 
 a more transparent nature. 
 
 As to the age, or perhaps more correctly the size, of the Echino- 
 coccus associated with the appearance of the daughter-bladders, only 
 an uncertain answer can be given. So far as I know, there is no 
 authentic case in which an Echinococcus smaller than a walnut con- 
 tained hydatids, which casts doubt on Davaine's statement mentioned 
 above. But that the production of daughter-bladders does not exclude 
 the formation of heads, is evident enough from the fact that along with 
 the latter one often sees bladders of all possible sizes, from that of an 
 apple to that of a pin-head, with all intermediate stages. 
 
 This continued proliferation explains also the large size of the 
 daughter-bladders, which is observable in many cases of hydatidose 
 Echinococcus. We know instances where the number might have been 
 estimated at thousands. 1 Most of these reports, however, are of 
 somewhat early date, and we are somewhat inclined to place them in 
 the same category as the reports of tape-worms 800 yards long. I 
 myself, I must confess, belonged to the ranks of these sceptics, until, 
 through Professor Luschka, I became acquainted with a case not a 
 whit inferior to any of these older reports. 
 
 The case was that of a woman sixty years of age, who for several 
 decades had suffered from a tumour which was for a while considered 
 as an extra-uterine foetus, until its increasing size and the absence of 
 distinct confirmatory symptoms led to the abandonment of this 
 diagnosis. On post mortem examination the tumour was seen to be 
 a huge Echinoccocus, which originated in the liver, and had gradually 
 grown to become a sac weighing thirty pounds. Within it there was 
 an immense number of daughter-bladders, some thousands at least, 
 varying from the size of a fist to that of a pea and less, but neither 
 heads nor hooks could be found. 
 
 Echinococci with some hundred bladders are more frequent, but 
 as a rule the number remains below this, and is often about 25-50. 
 These differences depend partly, but not wholly nor exclusively, on 
 the age of the Echinococcus. In an Echinococcus weighing from eight to 
 
 1 Besides the cases collected by Davaine (loc. cit., p. 365), in which the number in 
 some cases amounts to 9000 ( !), I may also note Russell (Dubl. Journ. Med. Sci., vol. xii., 
 No. 35, 1837), and Knaffl (Oesterr. med. Jahrb., Bd. xx., Stuck 3 ; Schmidt's Jahrb., 
 xxviii., No. 10), where two cases of "several thousands" are reported. Even in the 
 domestic animals such cases occur. My uncle, F. S. Leuckart, once saw a fat pig whose 
 abdominal cavity was filled with "several thousand hydatids," which originated from a 
 recently ruptured Echinococcus in the liver, which it had almost entirely destroyed. 
 
FORMATION OF INTERNAL DAUGHTER-BLADDERS. 619 
 
 ten pounds taken by Leroux from the liver, there were hundreds of 
 daughter-bladders which varied between the size of a pea and that of an 
 egg j 1 while an Echinococcus weighing fifteen pounds, observed in the 
 thoracic cavity by my now deceased friend Kriiger in Brunswick, 
 contained only twenty-five bladders, and an Echinococcus of 12 pounds 
 found by Lelouis in the Douglas' pouch of a man contained only ten 
 about the size of nuts. 2 
 
 The number of enclosed daughter-bladders may indeed sink still 
 further, as is proved by two cases mentioned by Krabbe and by 
 Andral, in which two large Echinococci, occupying the whole lower 
 lobe of the lungs, enclosed in the one case two, and in the other 
 three small daughter-bladders. The number may, on the other hand, 
 greatly increase even at an early stage, as is proved, e.g., by a case 
 observed by Yelpeau, in which an Echinococcus about the size of an 
 egg, which had developed under the shoulder-blade, 3 on being 
 punctured set free at least a hundred bladders, of which the largest 
 were about the size of a hazel-nut, and the smallest hardly larger 
 than a pin-head. 
 
 From these instances one cannot but be convinced that the vege- 
 tative relations of the Echinococcus present great divergences, of which 
 the determinant factors are not yet clearly known. All the more 
 must we avoid forming judgments on the strength of presupposed 
 standards. 
 
 If the daughter-bladders be but few in number, so that they can 
 develop unhampered on all sides, then they have always a beautiful 
 and regular spherical form. In other cases the mutual pressure pro- 
 duces the most manifold shapes. Some are more or less compressed, 
 others constricted like a sand-glass, while others again exhibit three, 
 four, or more smaller flattenings. In spite of all differences of appear- 
 ance, these agree histologically with the simple Echinococci, as I need 
 hardly repeat after what has been said above. 
 
 The question readily suggests itself, How do these daughter-bladders 
 arise ? The answer is not so readily obtained. From the fact that 
 the so-called " secondary hydatids " are in their properties as 
 thoroughly identical with the mother-bladder as are the exogenously 
 produced daughter-bladders, one might reasonably suppose that they 
 originated in the same way, in other words, that they were developed 
 from small beginnings in the wall of the mother-bladder. Only this 
 difference would obtain between them, that in the simple Echinococcus 
 the daughter-bladders emerge on the exterior, while in the hydatid 
 form they appear and remain within the cavity of the mother-bladder. 
 This is in fact Kuhn's opinion, and was also mine in the first edition 
 
 1 Davaine, loc. cit., p. 456. 2 Ibid., p. 513. 3 Ibid., p. 544. 
 
620 
 
 VARIOUS FORMS OF ECIIINOCOCCUS. 
 
 of this work. I have now, however, come to a different conclusion. 
 For although the formation of peripheral daughter-bladders is to be 
 observed in the hydatidose Echinococcus, this takes place only in con- 
 nection with the multiplication of the hydatids, while they originate 
 by a different mode, namely, the heads and brood-capsules (which we 
 have shown to be morphologically equivalent to the bladders), undergo 
 a retrograde metamorphosis, in consequence of which they assume the 
 form and structure of daughter-bladders. 
 
 Bremser, v. Siebold, and Wagener had previously asserted such a 
 transformation in regard to the head, and Eschricht in regard to the 
 brood-capsules, but, the detailed proof being wanting, their statements 
 did not meet with the consideration which they deserved. But this 
 gap has been filled up by the publications of Naunyn and Rasmussen, 
 and the origin of the organs in question has been sufficiently estab- 
 lished. I must add, however, that Rasmussen differs to some extent 
 from Naunyn, inasmuch as he maintains that only the brood- 
 capsules wander about in the daughter-bladders, and denies that the 
 heads have this capability. But according to my own observations 
 he is mistaken on this point. In the Echinococcus of the sheep, I have 
 observed that the processes referred to by Naunyn may occur exactly 
 as he has described. In the Echinococci of this animal the occurrence 
 of secondary hydatids is by no means so rare as is generally supposed. 
 Naunyn also made his investigations principally on the Echinococcus 
 of the sheep, but was at the same time convinced that in the human 
 Echinococcus the hydatids originate in exactly the same way. 
 
 Among the countless heads which are found in the larger Echino- 
 
 cocctts-bladders, partly in the interior of 
 the brood-capsules, and partly free in the 
 fluid of the bladder, one not unfrequently 
 notices some which are modified in a 
 peculiar manner. They are more trans- 
 parent and larger than the others, and in 
 the inflated hinder part of the body 
 contain a cavity filled with a clear fluid, 
 through which a distinctly fibrous band, 
 which not unfrequently encloses vessels, 
 runs towards the heads. The character 
 of this cord seems to favour the supposi- 
 tion that it has originated by separation 
 from the middle layer. On the inner 
 surface of the body-wall, which accord- 
 ingly ought to correspond to the peri- 
 pheral layer of the body, are seen the ciliary lappets previously 
 
 FIG. 331. Metamorphosis of an 
 Echinococcus-hesid into a bladder in 
 the interior of the brood -capsule. 
 After Naunyn. (x 60.) 
 
FORMATION OF DAUGHTER-BLADDERS FROM BROOD-CAPSULES. 621 
 
 discussed, and also a network of fine threads, which proceeds from the 
 more compact anterior end, and exhibits several distended portions 
 enclosing fatty drop-like structures of various size. The outer cover- 
 ing is formed of a structureless cuticle, which becomes thicker with 
 the increasing size and roundness of the body, and exhibits a lamina- 
 tion which becomes more and more distinct. 
 
 Gradually the internal cavity passes from the posterior to the 
 anterior body. The suckers disappear, the calcareous corpuscles are 
 dissolved, and the parenchyma of the head, and the network which 
 we have mentioned, spread themselves equally over the wall of the 
 body in the form of a fine cellular layer. The circlet of hooks alone 
 reveals the origin of the bladder. But this also disappears when the 
 bladder is about the size of a millet seed, and then the former head 
 does not differ in a single point from a young Uchinococcws-bl&ddeT. 
 
 In cases where the modification of the heads begins in the interior 
 of the brood-capsule (Fig. 331), the latter bursts before the meta- 
 morphosis of the head is completed, 
 so that the young hydatids are all 
 found free within the bladder. 
 
 But it is not only the heads that 
 undergo this metamorphosis, but 
 under some circumstances also the 
 brood-capsules, and especially, it 
 would seem, those which have 
 already lost some of their heads. 
 The transformation begins with a 
 thickening of the hyaline membrane. 
 When this has proceeded so far that 
 the latter possesses the nature and FlG> 332. -Metamorphosis of the 
 
 lamination of a firm CUticle, the brood-capsules into bladders. After 
 
 bladder is set free from its basis. 
 
 The superficial parenchyma disappears, but in place of it a new 
 one orginates in the interior, formed from the substance of the heads, 
 which apply themselves to the cuticle, gradually lose their form, and 
 ultimately become a boundary layer, which is equally distributed 
 over the internal surface. The circlets of hooks, which may at first 
 be perceived in the interior, leave no doubt as to the origin of this 
 inner layer. But afterwards, when these have been destroyed and 
 have disappeared, it is impossible to find any indication of its origin. 
 The bladder then resembles a young Echinococcus, and all the more 
 closely, since the parenchyma again exhibits that reticular marking 
 which we have already often noticed in these bladder- worms. 
 
 In some cases this metamorphosis is somewhat modified, inasmuch 
 
622 VARIOUS FORMS OF ECHINOCOCCUS. 
 
 as it affects not the whole brood-capsule, but only a certain part of it, 
 which is then at an early stage marked off from the rest by a 
 constriction. 
 
 According to Easmussen, however, the laminated cuticle of the 
 secondary hydatids does not originate by the thickening of the hyaline 
 inner membrane, but upon the external surface of the brood-capsule, 
 which from the first is covered by a delicate cuticular layer. The 
 metamorphosis of the brood-capsules into hydatids would accordingly 
 be a kind of encapsulation, as was indeed previously asserted by 
 Eschricht. Any change of the parenchymal sheath would thus be 
 unnecessary, and its formation would be independent of the destruc- 
 tion of the heads, which in its turn would be a process of only 
 subordinate importance. 
 
 When once they have arisen, the secondary hydatids are also able 
 to multiply by external buds, and that in the very same way as we 
 have described in the simple Echinococcus. The investigations of 
 Davaine, as well as those of Levison and Easmussen, leave no doubt 
 regarding this point. The latter saw the proliferation even in hydatids 
 which hardly measured half a millimetre, while Davaine observed it 
 in older and larger daughter-bladders. 
 
 It has already been mentioned that the secondary hydatids also 
 correspond to the simple Echinococciis-blsiddeTs, as regards the pro- 
 duction of brood-capsules and heads. By this vesicular metamorphosis 
 these bladders can of course again produce hydatids in their interior, 
 so that three generations are then enclosed one within the other. 
 Even in sterile hydatids one sometimes finds granddaughter-bladders, 
 but it would seem that these owe their origin to no new formation, 
 but to certain heads which undergo their vesicular metamorphosis at 
 the same time as the enveloping germ-capsules, and without leaving 
 them. Naunyn mentions that he has often found such heads in the 
 interior of small hydatids which had been newly formed from brood- 
 capsules. 
 
 If, however, the secondary hydatids all originated in the way which 
 we have described, as the results of the metamorphosis of the heads 
 and germ-capsules (and against this view there are no d priori con- 
 siderations, since both structures are morphologically perfectly equi- 
 valent 1 to the bladder), then there could of course be no sterile 
 Echinococci with daughter-bladders in their interior. The Echinococcus 
 
 1 I may take this opportunity of mentioning that very often structures of the same 
 morphological value undergo a subsequent transformation. We know, for example, that 
 in crabs the swimming legs are transformed in the course of the metamorphosis into 
 mouth -appendages, and are functionally replaced by others subsequently formed. We also 
 know that the nutritive polyps of certain Tubularidee modify their former structure from 
 external and internal causes, and change into proliferating individuals (Blastostyles). 
 
DIRECT FORMATION OF DAUGHTER-BLADDERS. 623 
 
 hijdatidosus would thus always be capable of producing brood-capsules 
 and heads as well as daughter-bladders. 
 
 It is nevertheless equally certain, from the investigations of Helm, 
 which, being specially directed to this point, admit of no doubt that 
 there are hydatid Echinococci which are completely destitute of heads. x 
 In order to reconcile these forms with the above view, we must 
 suppose either that the worms had in the course of time lost the 
 capability of producing heads, or that the brood-capsules had become 
 daughter-bladders before the differentiation of the heads. 
 
 The possibility of these processes cannot be denied, but Naunyn 
 has in the meantime proved that under some circumstances the 
 secondary hydatids originate directly, and independently of the other 
 products of proliferation. 
 
 The process exhibited in this alternative mode of formation con- 
 sists essentially in the sacculation of the Uchinococcus-weill. This 
 begins by the collapse of the bladder after the partial loss of its fluid, 
 so that surfaces formerly opposite are here and there brought into 
 contact. When this contact, as often happens, leads to coalescence, 
 a portion of the parenchymal sheath separates like a fold from the 
 rest of the covering of the ^cAmococcws-bladder, and the portion of 
 the parenchyma thus separated forms the starting-point of the new 
 formation. First of all, it is changed by flattening and disappearance 
 of the internal cavity into a band, which in its turn generally breaks 
 up after a short time into a number of pieces. These become sur- 
 rounded by a system of concentric cuticular lamellae, and becoming 
 hollow inside, form so many new hydatids. The process bears the 
 greatest resemblance to the above - described exogenous budding, 
 except that when the hydatids grow out of the enveloping fold and 
 fall off, they do not make their way outwards, but into the bladder- 
 space. 2 
 
 In some cases the process which we have described is only im- 
 perfect, and then there arise forms in which the inner surface of the 
 cuticle (as both Eschricht and I observed) is covered with cauliflower- 
 like excrescences, which always enclose hollow spaces. 
 
 The two forms of Echinococcus which we have hitherto been con- 
 sidering, E. granulosus and E. Jiydatidosus, however different they may 
 be in other respects, agree at least in this, that they both form bladders 
 of considerable size. We know, for example, that they sometimes 
 
 1 Loc cit.; regarding this point, see especially Observations iv., ix., andxi. 
 
 2 Thus I was by no means wrong when I formerly sought, in the first edition of this 
 work, to derive the daughter-bladders of the Echinococcus hydatidosus from peripheral 
 buds, which essentially differ from the buds of the E. granulosus, only in reaching the 
 interior of the mother bladder by separation. I only erred in regarding this mode of 
 origin as the only one that ever occurs. 
 
624 
 
 VARIOUS FORMS OF ECHINOCOCCUS. 
 
 grow as large as or even larger than a child's head, which is, how- 
 ever, more frequently true of the Echinococcus hydatidosus than of 
 the other. 
 
 A third form of Echinococcus (E. multilocularis) differs from these 
 principally (apart from the first stages of development, which have 
 not yet been observed) in being composed not of a simple bladder, 
 but of a group of small, even very small, bladders, which lie in 
 considerable numbers near each other embedded in a common 
 soft stroma. 
 
 We find this Echinococcus multilocularis almost exclusively in man, 1 
 and indeed with few exceptions in the liver, 8 in which, along with 
 the stroma, it forms a usually somewhat round, firm body, about the 
 size of a fist or even of a child's head, and having at first sight more 
 resemblance to a neoplastic growth than to an animal parasite. 
 
 If a section be made through the tumour, numerous small cavities 
 are found in the interior, usually of irregular form, separated from 
 
 each other by a more or less thick connective- 
 tissue mass, and with somewhat transparent 
 gelatinous contents. In the intervening 
 mass there is seen here and there a blood- 
 vessel or a collapsed bile-duct. As far as 
 the tumour extends, the proper substance of 
 the liver has completely disappeared, so that 
 the limits of the former are distinctly defined, 
 and its extraction presents no great diffi- 
 culties. But occasionally there may be seen 
 issuing from the tumour a number of white, 
 pearly moniliform cords, and even thicker 
 off-shoots, which make their way into the 
 adjoining liver-parenchyma, and become new 
 foci of Echinococcus-ioTmsition at some dis- 
 FIG. 338. Section through tance from the tumour. 
 
 The alveolar structure of the tumour and 
 the associated gelatinous bladders remind 
 one so forcibly of certain colloid growths, that it is easy to understand 
 
 1 More recently, however, it has also been observed in the ox, for example by Huber 
 (Jahresber. d. naturhist. Vereins in Augsburg, 1861), Perroncito ("Degli Echinococci 
 negli animali domestici," p. 69, Torino, 1871), Harms (Jahresber. d. k. Thierarzneischulc 
 in Hannover, iv., p. 62, 1872), and Bollinger (Deutsche Zeitschr. fur Thiermcdicin, Bd. 
 ii., p. 199, 1875). In Huber's case, there were, beside the E. multilocularis, an E. hydati- 
 dosus as large as a fist, and a number of simple Echinococci (with heads) thus a collection 
 of all the forms which are known to us. 
 
 * Among the cases with which we are acquainted (about forty) there is only one in 
 which the E. multilocularis was certainly observed outside the liver, namely, in the supra- 
 renal body (Huber, Deutsches Archiv f. Idin. Med., Bd. iv., p. 613). It is true that the 
 
 an Echinococcus multilocularis 
 (nat. size). 
 
ECHINOCOCCUS MULTILOCULARIS AND COLLOID CANCER. 625 
 
 that the earlier observers never thought of doubting their pseudo- 
 plastic nature. And they must have been confirmed in this erroneous 
 opinion by the circumstance that the multilocular Echinococcus has 
 a peculiar tendency to central ulceration (originating at first in the 
 stroma), which generally causes the death of the host. Even the 
 observation of Zeller, 1 that the gelatinous bladders of the alveoli oc- 
 casionally contained a brood of JZckinococcus-hQ&ds, did not avail to 
 alter the prevailing opinion regarding the so-called " alveolar colloid " 
 of the liver. The presence of these animals was regarded as an acci- 
 dental complication, and the pseudo-plastic nature of the growth was 
 never doubted until Virchow ultimately established the complete cor- 
 respondence of the so-called " colloid masses " with small Echinococcus- 
 bladders. 2 
 
 Virchow's discovery removed all doubt on this point. The only 
 question was whether or not the individual JEchinococcus-\A&ddei8 of 
 the tumours originated independently of each other ; in other words 
 whether they owed their origin to an extensive, perhaps often repeated, 
 immigration of Echinococcus embryos, or were produced by continuous 
 budding from one, or perhaps a few mother -bladders. The latter view 
 seemed the more probable, and all the more since the early observers 
 had frequently noted the irregular form and numerous club-shaped 
 processes of the colloid Echinococcus-lol&ddeTS. 
 
 Virchow was therefore entirely in the right when he sought to 
 explain the form of the multilocular Echinococcus by the supposition 
 of a repeated external proliferation. It is more doubtful whether he 
 was equally right in supposing this peculiar form to be due to the fact 
 that the multilocular Echinococcus had taken up its abode in the 
 lymphatic vessels. At present, perhaps as much can be urged against 
 this conjecture as can be adduced in favour of it. Even if we suppose 
 that the root-like processes of the tumour (frequently observed, and 
 especially in Virchow's case) follow the course of the lymphatic 
 vessels, the primary position of the Echinococcus would be by no means 
 determined, since it is quite well known that the growing Echinococcus 
 not unfrequently seeks out the most diverse paths, and penetrates 
 with special preference into adjoining cavities, that is to say, into the 
 blood-vessels, and in the liver also into the gall-ducts. Indeed, we 
 have gradually become convinced that the multilocular Echinococcus 
 may be found on different occasions in all these cavities. 
 
 lungs (Lebert), the pulmonary artery, and the sub-peritoneal tissue of the uterus (Scheu- 
 thauer), and even the intestinal wall itself, are mentioned as the seat of E. multilocular is, 
 but all these statements are doubtful, since there is some suspicion that they refer to 
 multiple Echinococci. 
 
 1 " Das Alveolarcolloid der Leber : " Tubingen, 1854. 
 
 2 Verhandl. der Wurzburyer phys.-med. Gesettsck., Bd. vi., 1856. 
 
 2 R 
 
626 VARIOUS FORMS OF ECHINOCOCCUS. 
 
 Our knowledge of the primary position of the Echinococcus is 
 upon the whole so scanty, that we are far from being able to 
 utilise the differences in its occurrence for the explanation of the 
 different forms of Echinococcus. In pigs the Echinococcus of the liver 
 lies, as we have already mentioned, originally in the interlobular 
 spaces ; but whether in the lymphatics, bile-ducts, or blood-vessels, 
 which together form this capillary network, cannot be determined. 
 For my own part, I am most inclined to place the primary seat of the 
 Echinococcus in the blood-vessels, and I can at least urge in favour of 
 this opinion the analogy of Cysticercus pisiformis and C. tenuicollis, 
 and perhaps also the wide distribution of the Echinococcus itself. Vir- 
 chow, on the contrary, thinks that the multilocular Echinococcus 
 develops in the lymphatics, while Schroder van der Kolk, 1 Friedreich, 
 and Morin are convinced that it really originates in the gall-ducts. 
 
 My own acquaintance with the multilocular Echinococcus is based 
 on the investigation of some preserved specimens. Not only had 
 Professor Luschka the kindness to place at my disposal portions of 
 two tumours investigated by von Zeller and himself, 2 but I was also so 
 fortunate as to find an entire (though of course extracted) tumour in 
 v. Sommering's collection, which now belongs to the Giessen Uni- 
 versity Museum. 3 The latter, which is about the size of a duck's 
 egg, is flattened at one end, and has there a cavity of the size of a nut, 
 with walls irregularly eroded. This cavity unquestionably represents 
 the ulcerated cavity found quite constantly in specimens of Echino- 
 coccus multilocularis at a certain stage of development. As may be 
 seen from the above description, the Echinococcus-lA&ddeTS are on an 
 average larger than in the two other cases known to me, but otherwise 
 they perfectly correspond with them. 
 
 The nature of the material at my disposal has rendered it impos- 
 sible for me to add anything new to the earlier observations, and 
 particularly to the statements of Zeller and Virchow. Thus all that 
 I can offer hardly amounts to anything more than a confirmation of 
 what is already known. More recent observations 4 have in fact done 
 but little to advance our knowledge of the Echinococcus multilocularis. 
 
 The size of the cavities, and of the Echinococcus-\Aa,ddeTS which 
 
 1 Ruyssenaers, " De nephritidis et lithogenesis quibusdam momentis," Dissert, inaug., 
 Traj. ad Rhen., p. 49, 1844 (cited by Virchow). 
 
 8 See Virchow' s Archiv f. pathd. Anat., Bd. x., p. 206. 
 
 8 In the catalogue of this collection, numbered 215, with the note "Tumor hepatis 
 viri, similis Baillie Fasc. v., PL iii., Fig. 3." 
 
 4 See especially the statements of Friedreich (Archivf. pathol. Anat., Bd. xxxiii., 1865), 
 of Klebs (Handb. d. pathd. Anat., Bd. ii., p. 511, 1869), and of Marie Prougeansky, 
 ( " Ueber die multiloculare ulcerirende Echinococcusgeschwulst in der Leber," Inaugural- 
 Dissert., Zurich, 1873), and Morin (loc. cit.). 
 
PROLIFERATION OF ECHINOCOCCUS MULTILOCULARIS. 627 
 
 fill them, usually varies in such a manner that the largest cavities, 
 which sometimes have a diameter of 3 or 4 mm., are found in the 
 middle of the swelling. But between them are much smaller bladders, 
 and towards the periphery these gradually become more abundant, 
 bladders of less than O'l mm. being not unfrequently found. 
 
 All the bladders, even the smallest, exhibit the well-known 
 structure of the ^c/imococcws-bladder. They possess a laminated, 
 transparent cuticle of great elasticity and considerable thickness, 
 which, in the larger bladders, measures 0'08 mm. or even more, but in 
 the smaller ones sometimes only O01 mm. Occasionally one finds 
 bladders, even among the larger ones, with still thinner walls, so that 
 here, too, the same variations are observed which we noticed in the 
 newly developed SJchinococci. As in the latter, the interior of the 
 bladders is at first filled with a molecular mass, whose coarser granules 
 exhibit a distinctly fatty lustre. As soon as the bladder grows the 
 central space becomes clear, and the former granular contents appear 
 in the form of a membranous lining of the cuticle, with more or less 
 large and abundant calcareous corpuscles. In the parenchymal layer 
 of the larger bladders, Virchow very "frequently observed a large- 
 meshed network of anastomosing, stellate structures, somewhat swollen 
 at the nodes, and extremely fine in the connecting threads, which, being 
 embedded in the hyaline, structureless, intervening substance, pre- 
 sented the greatest resemblance to the stellate cells of the gelatinous 
 tissue. In some places the cells were larger, their processes and 
 connective threads broader and canal-like, their bodies larger (some 
 even 0*2 mm. long and O'l mm. broad), and with a more distinct 
 granular deposit. They had thus a very striking resemblance to 
 lymphatics in the course of development." There can be no doubt 
 that the structure thus described by Virchow, and afterwards in a 
 similar manner by Friedreich, is identical with that which I observed 
 in the large, still headless JEchinococcus-\Asid.dQTS. 
 
 But in the great majority of the bladders of this Echinococcus the 
 heads are never developed. In the foregoing cases I examined many, 
 both large and small, before finding a head, and such has been the 
 experience of earlier and more recent investigators, while many have 
 sought them quite in vain. In my observations the bladders which 
 contained the heads were usually of medium size perhaps 2 mm. or 
 more but the heads were always either isolated or in groups of three 
 or four. In size and form the hooks (36-42 in number) exhibited no 
 differences from those of the usual human JEchinococci. 
 
 Under some circumstances, however, the multilocular Echinococcus 
 attains a considerable fertility. So was it at least in a case from the 
 Zurich Hospital investigated by Marie Prougeansky, in which half 
 
628 VARIOUS FORMS OF ECHINOCOCCUS. 
 
 the bladders, both large and small, were provided with heads, so that 
 in single preparations one could count more than thirty. The smallest 
 bladders usually contained only one head, which almost filled the 
 whole interior; but others contained several, which were sometimes 
 of normal structure, and at other times had lost their hooks and 
 become calcified. Besides the heads, there were in the alveoli lami- 
 nated calcareous corpuscles and red haematoidin crystals, and occa- 
 sionally also accumulations of yellowish-brown bile-pigment. That 
 the heads are contained in brood- capsules is asserted only by Morin. 1 
 We have already mentioned that the bladders, both large and 
 small, have but rarely a regular spherical shape. Not only does the 
 wall of the latter often appear to be indented and folded, but one not 
 unfrequeutly finds bladders which are more or less deeply constricted 
 in the middle, while others have lateral protrusions of varying number 
 and size, which occasionally project outwards almost like a berry 
 (Fig. 334). 
 
 As Kuhn has already stated, similar racemose forms are found 
 in the common Echinococcus of cattle, 2 except that in this case the 
 protrusions are larger, and attain an average size 
 of 1 cm. I have inserted a drawing of this race- 
 mose Echinococcus, but unfortunately I am unable 
 to state its origin. The protrusions together en- 
 closed a single undivided hollow space, although 
 the communication was in many cases effected 
 FIG. 334. Echino- only by means of a narrow canal. I am not 
 coccus racemosus (nat ce rtain, indeed, whether there were not also some 
 isolated bladders in the neighbourhood of the worm. 
 If we think of this Echinococcus racemosus as enclosed in a common 
 thick stroma, in which the individual protrusions have each their own 
 alveolus, it is seen that the only difference between it and E. multi- 
 locularis is in regard to the size of the separate parts. 
 
 I think this resemblance justifies us in concluding that the 
 Echinococcus multilocularis, like Cysticercus racemosus (p. 554), originates 
 from primarily simple bladder-worms, and not, as was sometimes 
 supposed, from a large number of isolated Echinococci. 
 
 It is still, however, a moot-point whether the individual bladders 
 of Echinococcus multilocularis are always and exclusively formed by 
 inflated protrusions of the wall. As Virchow had before observed, I 
 have often seen upon the surface of the bladders tuft -like and club- 
 
 1 He says that only some of the heads were found in the brood-capsules, the majority 
 being situated directly on the parenchyma layer (loc. cit., p. 31). 
 
 3 See, for example, the case of Megnin above mentioned (p. 614). Krabbe also asserts 
 that in the liver of the sheep he has often found the Echinococcus-bladder " often somewhat 
 branched" Archivf. Naturgesch., Jahrg. xxxiv., Bd. i., p. 120, 1865. 
 
INTERLAMELLAR PROLIFERATION OF THE CYST. 629 
 
 shaped appendages, sometimes of microscopic size, which enclosed a 
 cord-like continuation of the parenchyma, and in their thickened end 
 not unfrequently exhibited an independent concentric lamination. 
 Sometimes the granular cord in the interior was interrupted, so that 
 the club-like end then enclosed a small cavity, with a granular mass 
 in the interior. 
 
 I think I am not wrong in interpreting these appendages as stolons 
 or sprouts that is to say, as structures which are equivalent to the 
 previously described buds, although they differ from them in so far as 
 they are continuations not only of the parenchyma, but also of the 
 cuticular wall of the mother-bladder. The ultimate fate is the same 
 in both cases, for the terminal portion of the sprout gradually becomes 
 a daughter-bladder, which not unfrequently 
 even becomes constricted off, and is then 
 associated with the others as an independent 
 structure. Klebs, indeed, is of the opinion 
 that the separate bladders of JEchinococcus 
 multilocularis are still connected with each 
 other, but I have repeatedly convinced my- 
 self of the opposite, although there is no FlGL *te.XtMmeoee** multi- 
 
 . ..,,, loculans. ( x 30.) 
 
 doubt that in many of the bladders, and 
 
 perhaps even in the great majority, there is a continuous connection 
 
 (at least of the cuticle). 
 
 According to all appearance, the bladders of the multilocular 
 Ecliinococcus originate from smaller or larger sacculated masses of 
 parenchyma, which are formed in the manner already described from 
 a folding of the cuticular wall and subsequent marginal growth. I 
 have even occasionally observed in my preparations what looked like 
 interlamellar buds. 1 To this category, perhaps, we ought also to refer 
 small sacs surrounded with a special cuticular layer, which Virchow 
 found in the wall of the larger bladders, and which he regarded as 
 originating in the interior of the above-mentioned stellate network. 
 In general, the multilocular JEchinococcus does not exhibit, in regard 
 to its proliferation, any important differences from the other forms. 
 Yet both Virchow and Schiess assert that in some bladders they have 
 observed several generations encapsuled one within the other. 
 
 The new bladders formed on the external surface remain, how- 
 ever, but rarely within the alveolar space occupied by the mother- 
 bladder. Usually, they very soon press into the adjacent and com- 
 paratively less compact stroma, forming a small special cavity, which 
 always closes after the separation of the buds, and then appears as 
 
 1 Morin also describes these interlamellar buds, and, as we have already mertioned, 
 sometimes even finds heads in them. 
 
630 VARIOUS FORMS OF ECHINOCOCCUS. 
 
 though the inhabitants had originated within it. The resemblance of 
 this to the primary Echinococcus cavity is all the more striking, since 
 the inner surface of the alveolus is covered with the same irregularly 
 formed granular cells which we have already described. Between 
 these one finds numerous fatty granules, haematoidin crystals, and 
 clot-like structures, which become more abundant the nearer one 
 approaches the ulcerated parts. Nor is there any lack of bile-pigment 
 and salts of lime. The latter sometimes impregnate the wall of the 
 cavity so abundantly (as is occasionally observed in other bladder- 
 worms), that they may be extracted from the alveolus in the form of 
 a more or less continuous shell. The intervening connective tissue 
 also often becomes the seat of a calcareous deposit, in which localities 
 the structure of the connective tissue is gradually destroyed. The 
 fibrils disappear, the fundamental substance becomes turbid and 
 granular, until the alveolar wall is ultimately changed into a caseous 
 mass, the destruction of which is followed by ulceration and formation 
 of lacunae. 
 
 If it were necessary to corroborate the parasitic nature of the so- 
 called "alveolar colloids" by further facts, we might refer to the 
 chemical character of the bladder-walls, which exactly correspond to 
 the cuticular membranes of the usual Echinococcus- bladders, of which 
 they are also the histological equivalents. We have already learned 
 from Frerichs the essential chemical properties of this substance, and 
 have seen that it belongs neither to the proteids nor to the gelatinous 
 tissues. The recent and minute investigations of Liicke l have con- 
 firmed these statements, and have proved that the cuticle of the 
 Echinococcus is chitinous, although it differs from the usual Arthropod 
 chitin in possessing less power of resistance against caustic alkalies and 
 boiling water. There are, however, many differences between the 
 older and younger JEchinococcus-\)la.ddeTS, not only in their behaviour 
 towards 1 reagents, but also in their elementary composition, 2 and in 
 the analysis of their ash. 3 By the proper application of sulphuric 
 acid and hot water, the cuticle of the Echinococcus, like ordinary 
 chitin, may be partly changed into grape-sugar, although the amount 
 
 1 Archivf. palhol. Anat., Bd. xix., p. 189, 1860. 
 
 2 The results of Liicke's analyses are : 
 
 Old Bladders. Young Bladders. 
 Carbon = 45 "342 44-068 
 
 Hydrogen = 6 '544 6707 
 
 Nitrogen = 5 "1493 4 '478 
 
 Oxygen = 42 "9547 44747 
 
 3 This difference in the ash (young bladders = 1579 per cent., old bladders only = 0'28), 
 which consists principally of salts of lime, is so striking, that we feel inclined to ask whether 
 the membranes were in both cases equally freed from the inner parenchyma and from 
 the calcareous corpuscles ; but of this Liicke does not inform us. 
 
CHEMICAL CONSTITUTION OF THE BLADDER -WALL. 631 
 
 of sugar formed (50 per cent.) shows that they still contain a small 
 quantity of nitrogenous substance (" hyalin," Hoppe-Seyler). 
 
 From Liicke's investigations, it appears that grape-sugar is also 
 a somewhat common constituent of the fluid contained in the 
 JZchinococcus-blsiddQY, and that it occurs constantly in those cases in 
 which the parasite lives in or near the liver. It is, however, highly 
 improbable that this sugar is a product of the chemical metamorphosis 
 of the JjJchinococcus-cuticlQ. It is much more probable that it originates 
 in the liver and its veins, especially as the absorptive capacity of 
 the -ZfcAmococc^s-bladder is very great, and as the investigations 
 of Barker and Queckett in a case of Echinococcus in the kidney have 
 proved the presence in the interior of the bladder of crystals also of 
 uric acid, oxalic acid, calcium triple phosphates, and other earthy con- 
 stituents of the urine. 1 In this way may be explained the presence 
 of cholesterin crystals, which are often found in enormous numbers in 
 the fluid of JBckinococd from the liver, as also the occurrence of 
 haematoidin crystals, which have frequently been observed in the latter, 
 and are always to be found in the multilocular EcTiinococci. A case 
 investigated by Davaine contained hydatids, only some of which 
 contained these crystals, but all of which were furnished with cal- 
 careous corpuscles of exactly the same deep red colour. 2 The pre- 
 sence of these blood constituents indicated an ecchymosis, which had 
 taken place some time previously, by a rupture of the vessels passing 
 through the wall of the cyst. 3 In Cysticercus pisiformis and C. 
 tenuicollis I have under the same circumstances occasionally seen 
 the whole fluid of the bladder of a blood-red colour, and so may it 
 have been in these EcTiinococci before the hsematoidin crystallised out. 4 
 
 It has long been known that in its normal condition the fluid 
 within the Echinococcus is almost entirely devoid of albumen, and 
 therefore does not coagulate on boiling. This also corresponds with 
 its low specific gravity (1009 to 1015). But instead of albumen it has 
 abundance of leucin and ty rosin. Heintz has also proved that it con- 
 tains succinic acid, which is found in hardly any other living organism. 
 Lucke is indeed of opinion that the body in question does not quite 
 correspond to succinic acid ; but Naunyn has in the meantime con- 
 firmed Heintz's discovery, and has also found inosite in the fluid. 5 Half 
 of the 1'5 per cent, of inorganic substance consists of common salt. 
 
 1 Barker, " On Cystic Entozoa in the Human Kidney," p. 9, London, 1856 (quoted 
 by Davaine). 
 
 2 Mtm. soc. biol, p. 107, 1855. 
 
 3 In this way is also explained the constant occurrence already mentioned of 
 haematoidin crystals in the ulcerating multilocular Echinococcus, 
 
 * Davaine indeed reports a case in which Echinococci of a red colour were expectorated. 
 6 Mullens Archivf. Anat. u. Physiol, p. 921, 1863. 
 
632 OCCURRENCE AND MEDICAL IMPORTANCE. 
 
 Occurrence and Medical Importance. 
 
 Davaine, " Traite" des Entozoaires," pp. 359-620, pp. 644-656. 
 Neisser, " Die Echinococcenkrankheit :" Berlin, 1877. 
 
 Marie Prougeansky, " Ueber die multiloculare ulcerirende Echinococcusgeschwulst in 
 der Leber," Inaug.- Dissert., Zurich, 1873. 
 
 Boecker, "Zur Statistik der Echinococcen," Inaug. -Dissert., Berlin, 1868. 
 
 Among human parasites none can compare with the Echinococcus 
 in the variety of its occurrence. Even the Cysticercus cellulosce, which, 
 on account of its residence in such different organs, has been rightly 
 described as one of the most widely distributed helminths, is in this 
 respect far behind the Echinococcus. There is hardly an organ of the 
 human body in which it does not occasionally dwell even the bones 
 being occasionally infested by it. 
 
 All these organs, however, do not contain the worm with equal 
 frequency. Like Cysticercus cellulosce, the Echinococcus has favourite 
 situations, and others which it visits less frequently, or perhaps only 
 rarely. The favourite seats of the two parasites are, however, very 
 different. The intermuscular connective tissue, for which the Cysti- 
 cercus has a special preference, is but rarely the seat of the Echinococcus. 
 In the brain, and especially in the eye, the Cysticercus is found far 
 more frequently than the Echinococcus; this in its turn has a special 
 preference for the viscera, which are avoided by the other, and above 
 all, for the liver. Neisser, who has given a very accurate and almost 
 complete account of the cases of Echinococcus hitherto observed in 
 man, and who has increased the 367 observations 1 of Davaine 
 (in 1860) to the large number of 986, mentions in his table no fewer 
 than 451 Echinococci in the liver, so that these almost amount to half 
 of all the cases recorded. After the liver in the scale of frequency, 
 we find the lungs and pleura with eighty-four distinct cases, the 
 kidney with eighty, the muscles and dermis (including the orbit) 
 with seventy-two, the brain with sixty-eight (spinal cord with only 
 thirteen), the female genitalia (including the mammae) with forty- 
 four (the male with only six), the true pelvis with thirty-six, the 
 circulatory apparatus with twenty-nine, the spleen and bones with 
 twenty-eight, the eye with three, and so on. Finsen, whose ob- 
 servations only extend over 255 patients, all of them Icelanders, 2 
 
 1 Boecker, who only makes use of materials from the Berlin Hospital, reckons 
 altogether thirty-three cases. Of the earlier accounts, I mention particularly von 
 Liidersen, " Dissert, de hydatibus," Gottingen, 1808, and von Rendtorff, " De hydatidi- 
 bus in corpore humano repertis," Berolinae, 1822. 
 
 2 " Bidrag til Kundskab om de i Island endemiske Echinococcer, " Ugeskr. for Lcegcr, 
 Bd. iii., p. 71, 1867. 
 
MULTIPLE ECHINOCOCCI. 633 
 
 estimates the number of Echinococci in the liver at 69 per cent., and 
 those of the abdominal thoracic viscera (lungs only 3 per cent.) 
 altogether at 95 per cent., so that the extra visceral occurrence appears 
 to be rather the exception. 
 
 As a rule, the number of Echinococci which attain development in 
 man is limited to one or to very few, which are then found either in 
 neighbouring organs, or more commonly in the same. Where only 
 one organ suffers, it is almost always the liver. But curiously enough 
 in man this organ is but rarely tenanted by a large number of 
 Echinococci, such as one sometimes finds in the animals used for food, 
 and especially in swine, whose liver is sometimes penetrated by 
 hundreds of distinct Echinococcus-bl&ddQrs. 1 There are, indeed, in- 
 stances in man where the number of Echinococci considerably increases 
 and the sphere of distribution becomes more extensive. In all cases 
 of multiple Echinococci the liver is probably one of the affected organs, 
 but the majority of the parasites are nevertheless usually found in 
 other parts, especially in the onientum and peritoneum, but also in 
 the lungs, spleen, and kidneys. Thus Wunderlich 2 describes a case 
 in which, besides a hydatid Echinococcus in the liver as large as a 
 child's head, there were in the spleen, in the retro-peritoneal space, in 
 the omentum, behind the csecum, in Douglas' pouch, twelve other 
 bladders, varying from the size of an apple to that of a fist, while 
 under the mesenteric coating of the small intestine there were about 
 half a hundred " dried " Echinococci, whose size varied from that of a 
 poppy-seed up to that of a bean. 
 
 In another case reported by Davaine, 3 the liver contained a large 
 number of small Echinococci, which projected only slightly from the 
 surface, but beside these were two larger sacs, of which one contained 
 at least three pounds of fluid, with many daughter-bladders, some of 
 them of the size of an egg. There were also numerous larger 
 Echinococcus-lalsidders in the true pelvis, between the bladder and the 
 rectum, in the gastro-hepatic and gastro-splenic ligaments, in the wall 
 of the transverse colon, and in the neighbourhood of the caecum, 
 besides numerous small bladders, some only the size of peas, under 
 the peritoneal coating of the intestine. 
 
 In the absence of exact reports it is difficult to determine with 
 certainty the number of the bladders in such cases. Wunderlich 
 
 1 Through the kindness of Professor Nitsche in Tharand, I lately received half of a 
 pig's liver, which was penetrated by hundreds of (sterile) Echinococci, about the size of 
 nuts, whose cysts lay so close to each other that the liver substance was largely compressed, 
 and in spite of its weight of thirty-six pounds, was really little more than a trabecular 
 structure of connective tissue, in which the bladder-worms were embedded. 
 
 2 Archivf. physiol. Heilk., p. 283, 1858. 
 8 Mtm. soc. biol, p. 106, 1857. 
 
634 OCCURRENCE AND MEDICAL IMPORTANCE. 
 
 designated the above-cited case as exhibiting " countless JSchinococci" 
 but in point of fact they are reduced apart from the secondary 
 hydatids of course to less than a hundred. It seems to me also that 
 the <; thousands " spoken of by Kuchenmeister in the last edition of 
 his work on parasites are the result of a similar excessive estimate. 1 
 
 But even if the number should not be much over a hundred, it is 
 large enough to suggest the question whether we have here the result 
 of a single infection. 
 
 When we consider that the multiple Echinococci exhibit usually 
 very considerable variations in the size and development of the 
 bladders, we are inclined at first to suppose that a repeated importation 
 of the Echinococcics-\)Tood. has occurred. The above-mentioned dis- 
 parities would then be readily explained by a supposition not in 
 itself improbable. Nevertheless I believe that a repeated infection 
 with the Echinococcm-brood must be very rare, for even a single 
 infection demands the co-operation of manifold factors. In certain 
 cases of Cysticercus celluloses we might admit the supposition without 
 difficulty, but here the conditions are essentially different, since the 
 Tcenia solium, which furnishes the material for infection, is much 
 nearer to man than the T. cchinococcus, whose eggs only reach us from 
 the dog. 2 
 
 If, then, the multiple Echinococci are to be referred to a single 
 infection, it does not follow with absolute certainty that they are all 
 of the same age. The .^cAmococms-bladders have, as we know, the 
 power of proliferation, and even of manifold proliferation ; it is 
 therefore possible than in the multiple Echinococci, in addition to the 
 first immigrants, we have their descendants. 
 
 We think first of the possibility of an exogenous proliferation a 
 process which does indeed come into consideration in explaining the 
 multiple Echinococci. But this supposition is only admissible when 
 the bladders, large and small, lie close beside one another, or at short 
 intervals. But, as a rule, the multiple Echinococci are scattered over 
 different, often widely separated organs, so that this explanation is 
 insufficient. For such cases one must refer to the observations of 
 Naunyn and Rasmussen, who have shown that heads and brood- 
 
 1 In the description of one of the two cases observed by Kuchenmeister we read as 
 follows (loc. cit. t p. 214) : "All the organs of the pelvic cavity were filled with 
 Echinococcus-bl&dders from the size of a hazel nut or walnut to that of an apple or a fist. 
 There must have been towards a thousand." No enumeration, however, is made, and the 
 approximate estimate cannot be right, since 1000 bladders, even of the size of a walnut, 
 would fill about a cubic foot, more than the whole contents of the pelvic cavity. Even the 
 "many hundreds," to which Kuchenmeister has now reduced them, must surely be still 
 too high an estimate. 
 
 a I repeat that Kiichenmeister's supposition of the occurrence of Tcenia echinococcus in 
 man (and also in the pig, the ox, the sheep) is quite baseless. 
 
ORIGIN OF MULTIPLE ECHINOCOCCI. 635 
 
 capsules do sometimes change into hydatids. Of course there is the 
 further difficulty that one must suppose that the primary Echinococcus 
 has first opened into a vessel, and liberated its brood-capsules or its 
 heads into the blood, which then transports them hither and thither. 
 The possibility of this would admit of experimental verification. I 
 regret that I have found no opportunity for so doing, and that the 
 more since I do not share Neisser's a priori objections to this mode of 
 explanation, although I am but little inclined to lay much stress on it. 1 
 
 It seems to me most probable that the multiple Echinococci, or at 
 least the great majority of them, are the result of a single infection, 
 but of one which furnished not one but many embryos. The above- 
 mentioned differences in size and development are easily explained by 
 remembering that the embryos are exposed to diverse external con- 
 ditions, so that some grow more quickly, and to a larger size than 
 others. This idea is confirmed by experience. In examining the 
 animals upon which I had experimented, I have often found consider- 
 able differences in the size and development of bladders, which 
 originated from the same feeding. If such differences be noticeable 
 in worms only a few weeks old, how much greater must they be in 
 the course of a life of years or perhaps decades. 
 
 Probably it is . not only multiple Echinococci which owe their 
 origin to an invasion of numerous embryos. Among the cases of 
 solitary Echinococci it may be that many originated from a more or 
 less abundant infection. We know, too, that it is not exclusively the 
 number of imported germs which determines the issue of a helmin- 
 thological experiment, but also the sum total of the circumstances 
 under which the introduction and development of the young brood 
 occurs. Most emphatic, perhaps, is the fact that the Ccenurus, which 
 is generally found solitary, is not always so from the first. "We may 
 therefore with some probability suppose that the solitary Echinococcus 
 often acquires that characteristic by a sort of selection. There are at 
 first, perhaps, a large number of young Echinococci, of which one (or a 
 few) gradually predominates over, and finally suppresses, the others. 
 When we consider that the disease usually calls for attention only 
 after persisting many years, we can understand why but few of these 
 degenerated Echinococci have been found. I may take this opportunity 
 of recalling the fact that in certain organs the Echinococci are found 
 associated in large numbers much more frequently than in others. 
 
 1 I must leave it undecided whether Morin (loc. cit., p. 34) is right in claiming an 
 embolic origin for the small Echinococci found by him in the lung of a patient infested 
 with a multilocular Echinococcus. He leaves the nature of the embolism undiscussed, but 
 it appears as though he were thinking more of daughter -bladders than of heads or brood- 
 capsules. 
 
636 OCCURRENCE AND MEDICAL IMPORTANCE. 
 
 While it is extremely rare that more than five or six Echinococci 
 develop in the liver or lungs of man (there are a few cases where 
 the liver contained twenty) one finds in the peritoneal coat of the 
 abdomen or in the omentum hardly a single example of a solitary 
 Echinococcus. 
 
 After what has been proved in regard to the natural history of Tcenia 
 echinococcus, there can be no doubt as to the origin of the Echinococci. 
 The Echinococcus-bladdeis are descended from the tape-worm, and 
 where they occur an importation of the tape-worm brood must have 
 preceded, all creatures suffering from Echinococcus, whether man or 
 beast, must in some way or other have become infected with the eggs or 
 proglottidcs of the Tcenia, and have had the enclosed embryos liberated 
 by the action of the digestive juices. After their liberation these 
 embryos must have bored through the intestinal walls, * and have more 
 or less directly reached their subsequent position. This internal 
 wandering may be effected through the blood-vessels or lymphatics, 
 and this view is supported by the preference of the worms for the 
 liver, which is rendered easily accessible by virtue of the portal 
 circulation. That all the Echinococci are not found in the liver is no 
 contradiction, because the embryos may readily pass by the lymphatics 
 into the venous system. 
 
 Since the Tcenia echinococcus inhabits especially the intestine of 
 the dog, and since the dog is the only host known to us which comes 
 into close association with man and domestic animals, ive can hardly 
 be in error if we regard it as the only source of the Echinococcus disease. 
 
 We need hardly show how cattle, &c. may infect themselves with 
 the eggs or proglottides of T. echinococcus. The proglottides voided 
 by the dog so constantly and in such numbers for the tape- worm, as 
 we know, lives socially, and often occurs in thousands are either 
 eaten with the dung, as by swine, or are carried by their own and by 
 external movements on to substances which serve as food, and thence 
 into the intestine of cattle and other herbivorous animals. Sometimes 
 only the eggs and not the proglottides are thus transported, but the 
 result is the same, provided the eggs have not in the meantime lost 
 their power of development, or fallen into an unfavourable environment. 
 
 But how are they introduced into man. Primarily, of course, and 
 most frequently, in consequence of accidental contact, as we explained, 
 in connection with Cysticercus cellulosce. In the latter case the infecting 
 material has its origin in man himself, in the present case in an animal 
 which lives near man, sharing lodging, food, and sometimes even bed 
 
 1 I cannot support Neisser's idea that the six-hooked embryos are quite passive in their 
 transmission through the tissue, like silver grains in Argyriasis, since they are by no means 
 so motionless as Neisser seems to suppose. See p. 322. 
 
FREQUENCY OF OCCURRENCE. 637 
 
 with him ; but this point of difference is of little consequence. In the 
 latter case, as in the former, both proglottides and eggs may in many 
 ways be carried in food or on the hands to the mouth, and thus reach 
 the intestine; and that the more readily, since dogs are fond of 
 licking the hands or faces of their masters, and equally fond of snuffing 
 at the anus or dung of other dogs. They may thus be in a sense inter- 
 mediate hosts, and yet themselves remain free from the adult Tcenia. 
 
 Too familiar association with dogs is, indeed, anything but safe, 
 and that especially in places and under circumstances (such as 
 sausage-manufactories and slaughter-houses) where the dogs can 
 readily obtain portions of JSchinococcus-bl&ddQYS, and develop them 
 into sexually mature tape-worms. We must prevent dogs from 
 licking us, banish them from room and kitchen, keep them clean, and 
 see that their excrement is as far as possible removed. Further 
 suitable precautions should be taken to prevent an infection with 
 embryos of Echinococcus ; the dogs should be kept away from places 
 where the bladders are thrown carelessly away, or even given to 
 dogs as tit-bits. The careless disposal of these "water-bladders," 
 and the unnecessarily large number of dogs, have most to do in 
 perpetuating and propagating one of the most severe and dangerous 
 forms of helminthiasis. 
 
 From the universal distribution of the dog, as well as of herbi- 
 vorous domestic animals, that is to say, of those creatures which mainly 
 facilitate and provide for the cyclic development of Tcenia echinococcus, 
 it is easy to suppose that the cystic worm is everywhere developed in 
 man. Experience has completely established the accuracy of this 
 conclusion, for we now know not only of cases of Echinococcus from all 
 parts of the world, but are also acquainted with the fact that in some 
 countries the disease is endemic, and endangers the health and life of 
 the inhabitants more than any other illness. 
 
 Among these countries is Iceland, where the Echinococcus disease 
 (the so-called " liver plague ") is so frequent that the Danish govern- 
 ment was compelled to send thither a special expert to investigate 
 its causes, and check its further spread by suitable arrangements. 
 Although indigenous there for centuries, the parasitic nature of the 
 disease was only discovered about thirty years ago, indeed, by Schleis- 
 ner, 1 who spent two years in the island for medical purposes. On the 
 ground of his own investigations and of the testimonies of the local 
 physicians, he estimated the number of patients suffering from hydatids 
 at one-sixth to one-eighth of the whole population, that is to say, 10 to 
 15 per cent., or altogether about 10,000 persons. Although Thorstensen, 
 who practised in Iceland for more than twenty years, also believes that 
 
 1 " Island, undersogt fra et laegevidenskab. Synspunkt :" Kjobenhavn, 1849. 
 
638 OCCURRENCE AND MEDICAL IMPORTANCE. 
 
 every seventh individual suffers from this disease, it has gradually 
 been established by means of more accurate statistics that these early 
 statements were exaggerated. 1 According to the reports of the medical 
 officer Finsen, who, in his district, which comprehended a seventh 
 part of the whole island, had a yearly average of between 700 and 
 800 patients, there were among that number twenty-four persons in- 
 fected with Echinococcus, and thus about 3 per cent. Among the 
 10,000 inhabitants of this district, he knew altogether 119 Echinococcus 
 patients (about 1/2 per cent.), and this of course without taking into 
 account those in whom the development of the parasite had not } r et 
 given rise to pathological disturbances ; when we further consider 
 that it is probable, especially in regard to the more remote parts of 
 the district, that all the patients had not come to the knowledge of 
 the physician, the number of the real Echinococcus patients in Finsen's 
 district (in the north of Iceland) may be estimated at about 2 per 
 cent, of the population. It certainly appears as though the Echino- 
 coccus were more frequent in some of the agricultural districts, and 
 especially in the east of Iceland, but Krabbe has shown that this pre- 
 ponderance is almost compensated by the relative rarity of the para- 
 site in those neighbourhoods where there is more fishery and trade, as 
 in Keykjavik, so that the total number of the Icelandic patients can 
 hardly be estimated at more than 1500 ( T V) of the population. Still 
 that is a very large number, much larger at any rate than is found 
 anywhere else. 
 
 In Iceland JZchinococcus-\)}&ddeTS are much more frequent in oxen 
 and sheep than in man ; a but, although present in considerable 
 numbers in these animals, they hardly ever attain the same size as in 
 man, and as they frequently shrivel up and calcify, they do not 
 cause such important disturbances of health. 
 
 As the inhabitants are chiefly engaged in the rearing of cattle, the 
 number of these animals is so great that there are eleven for every 
 man, as opposed to 1/8 in the kingdom of Denmark ; and, as the flesh 
 of the slaughtered animals is usually handled in a very careless, dis- 
 orderly, and uncleanly manner, it is not difficult to believe that 
 Tcenia echinococcus is of most frequent occurrence among the dogs. 
 
 1 On this subject see in Ugeslcriftfor Lager (1862-66), a paper on the Icelandic Echino- 
 cocci, which is translated by Krabbe in Archiv f. pathol. Anat., Bd. xxvii., p. 225, and 
 one on the Echinococci of the Icelanders, Archiv f. Naturyesch., Th. i., p. 110, 1865. 
 [This subject has been recently treated by Fonassen ("Echinokokkensygdomen belyst ved 
 Islandske Lsegers Erfaring : " Kjobenhavn, 1882), who estimates the number of patients 
 on the average at 1'3 per cent, of the population. R. L.] 
 
 2 Hjaltalin, who, in 1870 (Dobell, "Report on Iceland," London, 1870) still main- 
 tained that one-sixth to one -seventh of the population suffered from Echinococcus, estimates 
 the number of sheep infected with the parasite at one-fourth. 
 
GEOGRAPHICAL DISTRIBUTION. 639 
 
 Krabbe found it to be forty-seven times more frequent in the dogs of 
 Iceland than in those of Copenhagen, and discovered its presence in 
 about a third of the animals which he investigated, or in 28 per cent., 
 as against 0'6 per cent, in Copenhagen. Thus, when we consider, in 
 conclusion, that in Iceland there is a dog for every eleven persons (in 
 France for twenty-two, in Baden for forty-nine, in England for thirty- 
 five, and in Scotland for seventy-four), and that all these dogs have 
 intercourse with men and cattle, it is easy to see that millions of eggs 
 must be daily distributed by these animals, and that although the 
 majority of them may be destroyed, the remainder, which reach their 
 destination, are quite sufficient to give rise to the disease to the above- 
 described extent. The transmission of the embryo must be facilitated 
 by the want of cleanliness, which is especially prevalent among the 
 country people, and which is increased by the conditions of their 
 life, and particularly by the long duration of the winter, which is 
 spent by some in the same rooms with the dogs. The carelessness 
 with which the Icelanders carry on their intercourse with these ani- 
 mals must also frequently lead to infection, for they even go so far 
 as to allow their wooden dishes to be licked clean by the latter, instead 
 of washing them. Another fact to be taken into consideration is, that 
 the cool and damp climate preserves the vitality of the dispersed 
 germs much more effectually, and for a much longer time, than would 
 be the case under other circumstances. 
 
 Wherever similar circumstances occur, the Echinococcus disease 
 attains a similar distribution. According to Eichardson, 1 it is so in 
 Australia, among the inhabitants of the district of Victoria, and espe- 
 cially among the shepherds, also among the Buratis, whom we have 
 already had occasion to mention as the hosts of Tcenia saginata. At 
 all events, Kaschin states that in nearly all the post mortem examina- 
 tions which he made, he found " hydatids " in the liver and heart 
 which could hardly have been anything else than Echinococci. z The 
 accounts which are given of the mode of life and customs of this 
 nomadic people support this conjecture. We learn, for example, that 
 in unfavourable weather, and particularly in winter, the Buratis live in 
 the same tents (jurten) as the cattle and dogs, and in the most loathsome 
 state of filth and uncleanliness, since they wash neither their dishes 
 nor their own bodies, and wear their clothing until it falls to pieces. 
 
 1 Edinb. Mcd. Journ., p. 525, 1867. The eating of raw flesh, which is, according to 
 Richardson, the means by which the shepherds are infected with Echinococcus, cannot, of 
 course, be so unless the dogs have by chance deposited on the flesh the proglottides and 
 eggs of their Tania:. [See also Thomas, ' Hydatid Disease, with special reference to its 
 Prevalence in Australia," Adelaide, 1884: in Victoria Echinococcus occurs once in 
 18,800 ; in South Australia once in 23,000 inhabitants. R. L.] 
 
 2 Petersburg Medical Journal (Russian), vol. i., p. 366, 1861. 
 
640 OCCURRENCE AND MEDICAL IMPORTANCE. 
 
 In Algiers the Echinococcus seems somewhat widely distributed 
 both among the aborgines and Europeans. It is also frequent in 
 Egypt, but in America, so far as we know, it is rare. In Europe we 
 know of the occurrence of the Echinococcus in almost every country. 
 It is found, for example, in Italy, France, England, and especially in 
 Germany, from which the accounts are so numerous, and -so numeri- 
 cally exact, that they alone furnish us with tolerably satisfactory 
 statistics. In the literature of other countries we search almost in 
 vain for any numerical statements. We can indeed hardly learn 
 anything more than that, in 200 post mortem examinations made 
 by Leudet in 1855 in the hospitals of Rouen, he found Echinococcus 
 six times. I do not know what foundation there is for the statement 
 of Cobbold, that in England there are every year about 400 Echino- 
 coccus patients. 1 
 
 In his reports on the clinical institutes and hospitals of Germany, 
 Neisser 2 gives the number of cases as 153, and as this number was 
 found in about 500,000 persons who had been examined, the per- 
 centage may be estimated at 0*03. If we only take into account the 
 results of the post mortem examinations (ninety-five cases out of 13,882), 
 we shall of course obtain a much larger proportion (nearly 07 per cent.), 
 and if we add to this the 1812 autopsies, with two cases of Echino- 
 coccus, not mentioned by Neisser, in the Erlangen Clinical Hospital, 
 and also the 2002, with seven cases, in Dresden, 3 the number is raised 
 to nearly 0'6 per cent. Obviously it is principally the reports coming 
 from the north and middle of Germany (Rostock, Berlin, Gottingen, 
 Dresden, Breslau) that affect the result, with their ninety-four cases 
 of Echinococcus in 12,800 autopsies, while observations made in Prague, 
 Vienna, and Zurich (six cases in 2916 examinations, thus about 0*02 
 per cent.) make hardly any difference. 
 
 The Echinococci are thus considerably more frequent in the middle 
 and north of Germany than in the south, and the number of patients 
 even appears to increase as we go northwards. Yet we find from the 
 foregoing reports that among 261 post mortem examinations made in 
 Rostock 4 there were no fewer than twelve cases of Echinococcus, thus 
 giving a per-centage of 4'59, which is larger than in Iceland. On 
 
 1 Journ. Linn. Soc. Land., vol. ix., p. 292, 1867. 
 8 Loc. cit., p. 36. 
 
 3 Miiller, "Statistik, &c.," p. 14. 
 
 4 [It has recently been most unexpectedly shown that the Echinococcus is truly endemic 
 in Mecklenburg, especially its northern and eastern districts, as also in the neighbouring 
 districts of Pornmerania. The disease seems to be most widely distributed in Rostock, 
 where there is one patient in every 1414 inhabitants : the whole country shows one patient 
 in every 18,800 inhabitants. See "Beitrage Mecklenburger Aertze zur Lehre von der 
 Echinococcuskrankheit " herausgegeben von Madelung : Stuttgart, 1885. R. L.] 
 
INFLUENCE OF SEX, AGE, AND OCCUPATION. 641 
 
 the other hand, the number of observations is so small, that it is quite 
 possible there has been some error. 
 
 It is almost unnecessary to say that the data which we have 
 obtained by clinical observations must not be held as directly appli- 
 cable to the general population. The proportion in which the Echino- 
 coccus occurs in the latter cannot at present be even approximately 
 estimated ; but at any rate it is much less frequent than Cysticercus 
 cellulosce, probably even in those districts of Germany in which it is 
 relatively most abundant. 
 
 The explanation of the variable frequency of the Echinococcus is 
 always to be found in the different occupations and modes of life of 
 the inhabitants. The extent to which cattle and sheep are reared, the 
 number and treatment of the dogs, and the varying degree of cleanli- 
 ness, are the principal factors by which it is determined ; and this is 
 true not only of the different countries which are geographically and 
 climatically distinct, but also of much more restricted limits. This 
 explains why the Echinococcus occurs more rarely in towns, and 
 especially in large towns, than in the country, where the slaughtered 
 meat is less strictly inspected, and the dog not only has more frequent 
 opportunities of becoming infected with Echinococcus-he&ds, x but is 
 allowed more unrestricted intercourse with man. Similarly, it appears 
 that herdsmen and shepherds, with the members of their family, 
 furnish an unusually large contingent to the number of Echinococcus 
 patients, and at any rate a much larger one than seamen, among 
 whom, as has already (1846) been shown by Budd, this bladder- 
 worm is extremely rare. The fact mentioned by Busk, that the 
 lower classes are more frequently subject to infection than the 
 higher, must be ascribed essentially to the want of order and cleanli- 
 ness among the former, and thus to circumstances which also affect 
 the frequency of Cysticercus cellulosce. On the other hand, we know 
 of persons of a higher rank who have been infected with Echinococcus, 
 usually, indeed, in consequence of two close intercourse with pet dogs. 
 To the same circumstance is perhaps to be referred the somewhat 
 mysterious preponderance of female patients, which, according to the 
 statistics of Neisser, amounts to nearly a third (210 : 148), and is all 
 the more striking, since it will be remembered that in Cysticercus 
 cellulosce we had to note exactly the opposite proportions. It is, how- 
 ever, true according to Finsen that this preponderance of the female 
 Echinococcus patients is also found in Iceland (255 : 181), where no 
 pet dogs are kept. 2 
 
 1 With this agrees the statement of Krabbe, that the dogs in which he found Tcenia 
 echinococcus came principally from the suburbs of Copenhagen, Archiv f. Naturgesch. , 
 loc. cit., p. 120. 
 
 2 We may take this opportunity of remarking that the cases hitherto observed of 
 
 2 S 
 
642 OCCURRENCE AND MEDICAL IMPORTANCE. 
 
 A fact that is still more remarkable than this preponderance of 
 the female JZchinococcus-hosts, is that more than half of the cases of 
 Echinococcus multilocularis which have hitherto been observed in man 
 (nineteen cases among thirty-five, according to Niesser) belong to 
 Switzerland ; and in Germany this form has been found almost ex- 
 clusively in the south, so that a case observed in Dorpat is quite an 
 exception. Yet these countries are precisely the ones in which 
 Echinococcus is otherwise rare. We can hardly agree with Klebs in 
 supposing that the reason of this peculiar phenomenon is to be found 
 in the prevalence of cattle-breeding, since the most that could be 
 inferred from this would be a frequent occurrence of the Echinococcus. 
 Perhaps, after we have learned the causes that give the Echinococcus 
 multilocularis its peculiar form, 1 we shall find a better explanation. 
 In the meantime we have so little light on the subject that we do not 
 even know whether the determinant factors are to be found in the 
 worm itself, or, as is certainly more probable, in the condition of the 
 environment (abode, nature of the enveloping cyst, &c.). 
 
 In regard to the age of patients suffering from Echinococcus, it is 
 quite certain from the reports of Neisser that, like Cysticercus celluloses, 
 the parasite occurs most frequently in persons between twenty and 
 thirty. No fewer than 55 per cent, are found within this period, 
 while the rest are distributed over various other ages, up to fifty and 
 sixty, but always occur in greatest numbers near the former age. It 
 is doubtful whether the infection also takes place within this time, 
 especially as we know that the Echinococcus grows but slowly, and 
 usually only causes great disturbances of health after an existence of 
 some years. For the same reason it is extremely rare for it to occur 
 in early childhood. Finsen operated on a boy of six, who had 
 harboured the Echinococcus since his first year; and Thorstensen 
 reports the case of a child of four, in whom the extirpated bladder- 
 worm (E. hydatidosus) had already attained the size of a child's 
 head. 2 
 
 So far as I know, these are the youngest, reliable cases of Echino- 
 coccus patients. It is, indeed, stated by Hammer that, in the case of 
 a newly born child, whose much distended abdomen proved a 
 
 multiple Echinococci have occurred almost exclusively in the female sex. Kiichenmeister 
 connects this fact with the looseness of the peritoneal covering of the female sexual organs, 
 which he thinks possibly favours the development of the parasite. 
 
 1 Morin finds the explanation of this phenomenon in the specific nature of the Tccnia 
 belonging to the Echinococcus multUocularis, but, except the peculiar geographical distri- 
 bution, he can urge nothing in support of this view beyond the fact that the feeding 
 experiments which he made with the multilocular Echinococcus yielded no positive results 
 (loc. cit., p. 37). 
 
 2 Krabbe, Archivf. pathol Anat., loc. cit., p. 232. 
 
RATE OF GROWTH AND PROGNOSIS. 643 
 
 hindrance to birth, and had to be opened, he found hydatids to be 
 the cause of the swelling, 1 but this has probably nothing to do with 
 the Echinococcus. The same may be said of Cruveilhier's case of a 
 child twelve days old, in whose liver there are said to have been some 
 calcified hydatid cysts. 2 The bladders found byHeyfelder 3 in the 
 placenta and umbilical cord of a foetus of seven months, are to be 
 referred to a so-called " hydatid mole," which, as is well known, has 
 nothing in common with the Echinococcus. 
 
 The slow growth is quite sufficiently shown by my reports of the 
 dissections of animals which had been used for rearing the Echino- 
 coccus. But under some circumstances this growth can be directly 
 observed in man. Velpeau, for example, reports a case of Echinococcus 
 in the neighbourhood of the shoulders, which in six months grew to 
 the size of a small walnut. In another case an Echinococcus similarly 
 situated grew within a year to the size of a fist. 
 
 The growth of the Echinococcus is, however, by no means the same 
 in all cases. It is affected by the position and character of the 
 attacked organ, by the form of the worm, and by individual circum- 
 stances of the most manifold nature. The hydatid Echinococcus seems 
 to have the longest and most continuous growth, and in time often 
 attains quite an enormous size. It is true that this requires years, and 
 even decades. We have already mentioned such a case, and several 
 similar ones are recorded in literature. 4 
 
 Thompson treated an Echinococcus of very large size, the first 
 traces of which had been observed thirty years before ; and Raynal 
 operated on a woman, in whom the swelling had gradually spread 
 during forty-three years over a considerable portion of the face, and 
 attained the size of a child's head. On incision numerous daughter- 
 bladders shot forth, which had a perfectly healthy appearance, and 
 some of which were only the size of peas. 
 
 As a rule, however, the Echinococcus comes sooner to an end, and 
 usually by causing the death of its host. Perhaps the great danger 
 of the Echinococcus is best shown by a paper of Barrier's, 6 in which 
 he mentions that of twenty-four cases with which he was somewhat 
 exactly acquainted, more than half terminated fatally during the 
 course of the first five years. Three Echinococci had an existence of 
 less than two years, eight of two to four, and four of four to six. Of 
 the rest, three caused death after six to eight years, two after eight 
 years, and four after fifteen, eighteen more than twenty and more 
 
 1 Neue Zcitschrift f. GeburtsTcunde, Bd. iv. 
 
 2 "Traits' d'anat. pathol.," xxxvii., p. 6. 
 8 Schmidt's Jahrb., p. 324, 1834. 
 
 4 See Davaine, loc. cit., p. 384. 
 
 6 "De la tumeur hydatique du foie," p. 36, These Paris, 1840 (quoted by Davaine). 
 
644 OCCURRENCE AND MEDICAL IMPORTANCE. 
 
 than thirty years respectively. The reports of Neisser, based upon 
 fifty-four cases, only differ in that comparatively the greatest number 
 of fatal cases occurred within the first two years (that is to say, from 
 the discovery of the parasite, and without taking into account the 
 time during which it had escaped observation). 
 
 The time which the Echinococcus disease takes to reach its termi- 
 nation depends upon various circumstances. Besides the greater or 
 less rapidity with which the parasite grows, it is mainly determined 
 by the physiological nature of the infected structure. But even in 
 the same organ the Echinococcus gives rise to a different prognosis 
 according to its situation ; thus, for example, it is by no means in- 
 different to the host whether a bladder- worm in the liver has developed 
 in the neighbourhood of the great vessels, or among the yielding 
 ventral coverings. Nor is the form of the parasite of little moment in 
 this connection, as is evident from the constancy with which the 
 multilocular Echinococcus leads to the death of the patient through 
 the ulceration of the intermediate tissue. 
 
 So long as the Echinococcus is but of small size, the disturbances 
 which it causes are trifling, unless it occur in a nerve centre, or, as is 
 very rarely the case, in the eye. But as the parasite increases in 
 volume, the seriousness of the disturbance increases. In itself pain- 
 less, it gradually produces a feeling of pressure and heaviness, which 
 continually augments. The affected organ becomes enlarged, and loses 
 its previous form and character. The surrounding body wall is raised 
 up, if it can yield to pressure, and the adjacent organs are displaced. 
 At the same time there sets in a series of functional disturbances, 
 which become more and more aggravated, and which, at first associated 
 with the increasing intruder, not unfrequently spread to adjacent 
 parts. The health of the victim becomes more and more completely 
 undermined ; nutrition suffers, circulation is disturbed, a condition of 
 marasmus results, and finally death supervenes with symptoms of 
 exhaustion, unless a previous dropsical or inflammatory attack bring 
 it about sooner. 
 
 The special symptoms of the Echinococcus disease vary, of course, 
 greatly according to the situation and size of the parasite. A parasite 
 occurring in the liver produces different pathological results from 
 those caused by one occurring in the kidneys or lungs. Even in the 
 same organ the results are very various. The different modifications, 
 as detailed by Davaine and Neisser, and discussed by Kuchenmeister, 
 cannot here be entered into fully ; we must restrict ourselves to a few 
 observations of more general interest. 
 
 In the first place it may be mentioned that the life-history of 
 Echinococcus exhibits hardly any factors fitted to produce a direct and 
 
EFFECTS CAUSED BY THE PRESSURE OF THE TUMOUR. 645 
 
 specific influence on the organism which shelters it. It might cer- 
 tainly be supposed that the process of immigration would cause dis- 
 turbances of this kind (and indeed Klichenmeister has lately expressed 
 himself of this opinion), but these could only result from an unusually 
 abundant infection, and this is almost excluded by the nature of the 
 adult Tcenia. In the next place, the irritation which the developing 
 parasite produces in its surroundings, has as a rule no further conse- 
 quences than the formation and thickening of the wall of the cyst 1 
 and the displacement of the surrounding tissue. 
 
 The danger of the Echinococcus disease, however, arises from the 
 effects of the pressure of the growing parasite, and this pressure is 
 moreover always increasing, since the growth of these worms, and par- 
 ticularly of the hydatid form, which is by far the most frequent in man, 
 is almost unlimited. In this respect the Echinococcus is exactly like 
 certain tumours, with which it was classed until the end of the last 
 century, and for which (at least during life) it may be still easily 
 mistaken. 2 
 
 This also explains how it is that, when the Echinococcus remains 
 small or dies early, it usually causes so little annoyance that its pre- 
 sence is perhaps only discovered upon post mortem examination. The 
 frequency of these latent Echinococci may be seen from the fact that 
 of twenty-two cases which Bocker collected from the results of the 
 Berlin Charite Hospital, only nine had been diagnosed during life. 
 Among twenty-three cases of Echinococcus, Frerichs found eleven 
 latent, and Neisser found as many as thirty-one among forty-seven. 
 
 The first and chief consequences of the pressure are that the adjoin- 
 ing vessels and glandular passages are compressed and rendered impas- 
 sable to a varying extent. (Edema, varicose veins, and congestions of 
 various kinds, are thus very frequent accompaniments of Echinococcus. 
 
 This pressure is most constantly manifested when the parasite is 
 developed in cavities with more or less firm limits, as, e.g., in the 
 thorax, where it occasions the most serious dyspnoea, or in the pelvic 
 cavity, and especially in Douglas' pouch, where its pressure both 
 anteriorly and posteriorly considerably impedes the passage of the 
 urine and the expulsion of the faeces. In women Echinococci thus 
 situated sometimes act as such hindrances to delivery that it can only 
 be accomplished after the puncture of the bladder. 
 
 1 We know cases in which this cyst wall (only in consequence of repeated inflamma- 
 tory processes) had attained a thickness of several centimetres. 
 
 * Even distinguished authorities upon abdominal tumours, such as Spiegelberg, Dum- 
 reicher, Baum, and Esmarch, have made mistakes of this kind, and while endeavouring 
 to perform ovariotomies, have found to their astonishment, instead of the degenerated 
 ovary, an Echinococcus. As a rule a simple puncture will be sufficient to avoid such an. 
 erroneous diagnosis. 
 
646 OCCURRENCE AND MEDICAL IMPORTANCE. 
 
 When the Echinococci develop within the hones, the latter are at 
 first eroded in proportion to the growth of the parasite. Afterwards 
 the walls become thin, and often to such a degree that a moderate 
 blow is enough to cause a fracture. Thus Dupuytren mentions that 
 in the case of a man who had a hydatid Echinococcus in the much 
 enlarged medullary cavity of his humerus, the latter broke when he 
 tried to throw. Sometimes the Echinococcus breaks through the hard 
 coating at some point, and then expands among the surrounding soft 
 tissues. This happens not only when the parasite is developed in the 
 cancellous tissue of the bone, but also when contained within the 
 enclosed cavities, if it be but near the boundary. The cases are by no 
 means rare in which the Echinococcus of the thorax breaks through the 
 ribs and expands between the muscles, or where that found in the 
 cranial cavity breaks through the bones of the skull and expands in 
 the antrum of Highmore or nasal cavity. Sometimes, instead of seek- 
 ing an independent path, the clefts and foramina already present are 
 utilised. Those especially are traversed which lead into the orbits, so 
 that in consequence of the intrusion eyesight is often lost, exophthal- 
 mus ensues, or the eyeball is wholly destroyed. 
 
 In considering these phenomena, we must not forget that the 
 Echinococcus in such cases is destitute of the firm connective-tissue 
 cyst, which otherwise surrounds it, and prevents it from exercising 
 a direct influence on the adjacent tissues. In this respect Echino- 
 coccus closely resembles the bladder-worms which also occur without 
 a capsule in the serous cavities. Besides, we must remember that such 
 a worm has, to an unusual degree, the power of adapting its growth 
 to its external relations, as we saw in noting that the differences in 
 form and size might be often directly referred to the unequal resis- 
 tance in the immediate environment. Where the connective-tissue 
 envelope yields to the pressure of the growing parasite, a diverti- 
 culum is formed, so that the protrusions and lobes of the irregular 
 Echinococcus are ultimately explicable by the same physical principle 
 as that according to which the external portion of the worm, when 
 in a superficial situation, projects from the surrounding parenchyma, 
 and continually grows further outwards. The point of least resis- 
 tance determines the direction of this growth, so that Echinococci 
 situated near the convex surface of the liver rise towards the thoracic 
 cavity, while those near its lower surface sink down into the abdomen. 
 
 The pressure exerted on the bladder-wall and on the neighbouring 
 organs frequently excites a more or less marked reaction. First, 
 inflammation sets in, which is either limited to the Echinococcus- 
 cyst, or spreads to the adjacent tissues, and then results in a more 
 or less extensive adhesion of the affected parts. The Echinococcus 
 
RUPTURE OF THE CYST INTO VARIOUS ORGANS. 647 
 
 becomes attached to the adjacent organs, now to the intestine or 
 kidney, now to the diaphragm or abdominal wall. 
 
 The inflammation entails further consequences. It leads to ulcer- 
 ation and destruction of the affected parts. The cyst-wall gives way, 
 and the Ecliinococcus protrudes like a hernia to a varying extent. The 
 diverticulum reaches spaces which were previously shut off from the 
 worm. In the one case it is perhaps the abdominal or thoracic cavity 
 which receives them ; in the other, it is the intestine or the lumen of 
 a vessel, according to circumstances. 
 
 If the diverticulum be but small, and the cavity into which it has 
 penetrated be surrounded by close and resistant walls, so that there 
 is a counterbalancing pressure, then the worm retains for a lengthened 
 period its original character. It fills the cavity, penetrating to an 
 ever-increasing extent. This is most frequently the case with the 
 multilocular Ecliinococcus, whose processes penetrate into the ramifi- 
 cations of the bile-ducts, as well as into the portal vein and lym- 
 phatics, and sometimes grow into them in such a way as to suggest 
 that the peculiar form of the Echinococcus is determined by the spaces 
 which it occupies. 
 
 In such cases the anatomical result is very much what we have 
 above described in the case of Echinococcus of the brain, or of the 
 pleural cavity, when it has left its original seat and expanded in the 
 neighbourhood. 
 
 But it is not always so. When, owing to the size and extensi- 
 bility of the newly occupied space, there results a lessening of the 
 resistance to the diverticulum from the cyst, then the latter continually 
 increases, and becomes more distended with fluid and hydatids, until 
 it finally bursts either spontaneously, or in consequence of some 
 external cause, and expels its contents. 
 
 This issue is extremely frequent in the larger Echinococci of the 
 viscera, which are mostly of the hydatid variety. From Neisser's 
 results we see that of 451 cases observed in the liver, the third part 
 terminated thus. The majority opened either into the alimentary canal 
 (forty-five cases), or, after perforation of the diaphragm, 1 into the 
 bronchi (thirty-one). In sixteen cases each the contents were emptied 
 into the body-cavity and pleural cavity, and a breach through the 
 abdominal wall was equally frequent. The large vessels (veins) and 
 
 1 To the cases of this sort, collected by Davaine (loc. cit., p. 440), I may add a new 
 one observed by Professor Blasius. The preparation is lodged in the Anatomical Museum 
 of the University of Halle, and bears the following label : " Pulmo et hepar sutoris 
 40 ann. n. Frauendorf. Inde ex annis 15 ex echinococcis hepatis aegrotus crebris 
 peritonitidis insultibus vexatur, postremis annis echinococcos bile tinctos cum sputis 
 ediclit. Pulmonis dextri lobus inferior echinococcus destructus per diaphragma cum 
 ductu hepatico dextri lobi hepatis anastomosin inivit." 
 
648 OCCURRENCE AND MEDICAL IMPORTANCE. 
 
 also the ureters and bile-ducts (though less frequently, because of 
 their smaller size), are also occasionally the seat of the rupture. In 
 some cases, a twofold rupture is observed in the same Echinococcus, 
 usually into intestine and lungs, or more rarely into the intestine 
 and ureter. 
 
 Such a rupture is more frequent in the Echinococci of the lungs 
 than in those of the liver, so that evacuation often takes place through 
 the bronchial tubes. Among the sixty-eight cases enumerated by 
 Neisser, no fewer than thirty-one had this issue, nine led into the 
 pleural cavity, while the rupture took place into the pulmonary veins, 
 intestine, and through the umbilicus once in the case of each. 
 
 Here and there a rupture has been observed in the Echinococci of 
 the pelvis, leading either into the body-cavity or to the exterior 
 through the female generative passages, and once (in Sibille's case) 
 through the perinseum. 
 
 The prognosis varies in all these cases according to circumstances. 
 First we must take into consideration, besides the intensity and extent 
 of the ulcerative inflammation caused by the rupture, the nature of 
 the affected organ. The more sensitive it is to external influence 
 the more unfavourable is the situation ; in many instances, e.g., where 
 the contents are poured into the pleural or abdominal cavities, the 
 case is almost hopeless. 
 
 In these cases the evacuation is followed by a violent inflam- 
 mation of the peritoneum or of the pleura, and this is usually rapidly 
 succeeded by death. Where the inflammation has a less serious 
 character this is probably due to the small quantity of the emptied 
 matter, and to its condition. Of importance, therefore, in this con- 
 nection are the differences in the number, size, &c. of the daughter- 
 bladders. 
 
 The state of the case is much more favourable when the rupture 
 has been effected directly to the exterior through the abdominal walls 
 or the intercostal spaces. This is especially the case when the 
 fistula is short, and when the emptying of the daughter-bladders 
 presents little difficulty. Under such circumstances the rupture 
 leads not unfrcquently to a perfect recovery, so that of late years 
 it has been sometimes artificially produced (by caustic paste according 
 to Re'camier) in order to effect a radical cure. Of course there are 
 also cases in which the rupture, whether natural or artificial, may prove 
 fatal in consequence of peritonitis, or of long-continued suppuration 
 and exhaustion ensuing. 
 
 When the Echinococci (even if E. hydatidosus) open into the 
 bronchise, or the intestine, recovery is usually only a question of time. 
 This is specially true in the case of rupture into the intestine, for 
 
RUPTURE OF THE CYST INTO THE BLOOD-VESSELS. 649 
 
 among the forty-three such cases cited by Neisser no fewer than 
 thirty-seven were cured, while in the cases where the contents were 
 evacuated by expectoration, only about three-fourths (twenty-three out 
 of thirty-one) recovered. From the intestine the expulsion of the 
 bladder contents is usually effected per anum, and only in the case 
 of ruptures situated high up per os. The expulsion is sometimes so 
 favourably accomplished that the hydatids reach the exterior un- 
 injured. Davaine mentions the case of a woman in Paris who was 
 thus suspected of laying eggs. In the majority of cases merely 
 membranous shreds are voided, and their true nature is sometimes 
 recognisable only by the help of the microscope. 
 
 Besides the above-named organs, the blood-vessels sometimes 
 receive the contents of the burst JSchinococcus. This may happen, for 
 example, if the parasite have been developed in the cardiac muscles 
 and burst through the endocardium after a longer or shorter period of 
 inflammation. Et may also occur in the liver or lungs, in which cases 
 the large vessels, and especially the veins, are affected by the worm 
 exactly as were the hepatic ducts or bronchiae. On the whole, such 
 cases are rare, and happily so, since they are almost always fatal either 
 gradually or more suddenly (by thrombosis). Professor Luschka had 
 the goodness to tell me of an interesting case of this sort, which I 
 note the more readily, since there are but few such observations 
 on record. It concerned a woman forty-five years old, who died 
 suddenly with symptoms of asphyxia, and yet without apparent cause. 
 On dissection the cause was revealed. In the region of the posterior 
 border of the liver there was an JHchinococcus about the size of a 
 child's head, which in the fossa venae cavse had broken through the 
 wall of that vessel, and there liberated its contents. The daughter- 
 bladders had reached the right chamber of the heart, and thence also 
 the pulmonary arteries, where they had induced an embolism which 
 rapidly caused death. When the obstruction of the pulmonary 
 arteries is incomplete, then, instead of sudden death, a more pro- 
 tracted disease ensues, that has essentially the same symptoms as 
 stenosis of the pulmonary artery, and, like it, is accompanied by 
 dilatation and hypertrophy of the right heart. 
 
 The situation is very different when the daughter-bladders pass 
 through the pulmonary vein into the current of the aorta, and thence 
 into the peripheral vessels ; the result being that the portions robbed 
 of their blood supply mortify. 
 
 The phenomena evoked by JHchinococcus in brain or eye are like 
 those occasioned by Cysticercus celluloses. Their intensity is, indeed, 
 greater, but that is sufficiently explained by the more prolonged and 
 more vigorous growth of the worm. In the interior of the eye it has 
 
650 OCCURRENCE AND MEDICAL IMPORTANCE. 
 
 been observed only a few times, and always associated with complete 
 loss of sight. The Echinococci in the brain are still more serious, and 
 have always, after a longer or shorter period, a fatal issue. 1 As a rule 
 the disease is first manifested by violent and continual pain in the 
 head and joints, not unfrequently as a decided neuralgia, accompanied 
 by giddiness, fainting, and vomiting. Sooner or later attacks of cramp 
 begin to occur with varying frequency, and sometimes of a decidedly 
 epileptic character. The sensory and cerebral functions are gradually 
 increasingly disturbed, voluntary movement is suspended, and death 
 supervenes sometimes after apoplectic ruptures and softening round 
 about the parasite. 
 
 Those in the muscles and peripheral organs (thorax, salivary glands, 
 oral cavity, &c.) are on the contrary almost harmless. They only act 
 as hindrances, impeding the functions, and are usually readily removed. 
 
 Since these superficial Echinococci are on the whole but rare, our 
 judgment as to the clinical importance of the worm can hardly be 
 thereby modified. We are forced to regard it as one of the most 
 dangerous parasites infesting man, dangerous because of the disease it 
 originates, dangerous also because we are in many cases, and these the 
 most serious, quite helpless against it. Since we can do so little to 
 dislodge this unwelcome guest, it is a weighty fact that Nature herself 
 sometimes sets a limit to the destructive work. As we have noted, it 
 by no means rarely happens that the Echinococcus dies either at an 
 earlier or later stage of development. The cause of this phenomenon 
 has usually been sought in certain conditions of the surrounding cyst. A 
 change is to be observed affecting the granular cellular layer over-lying 
 the bladder. This is at first not unlike a serous coating, but it begins 
 to become loose and turbid. It frequently changes into a creamy or 
 caseous mass, 2 accumulating ever more and more round the bladder- 
 worm. 3 The latter seems for a while hardly in any wise altered. But 
 on closer examination one is convinced that the parenchyma is softened 
 and has undergone fatty degeneration, that at some points it has been 
 separated from the cuticle, and that the heads swim about freely in 
 the fluid, and present a more or less altered appearance. At a later 
 stage this fluid is exuded. It collects round about the bladder-worm, 
 and forms a thick mass of a glue or honey-like character, being 
 more or less mixed with the granular substance of the cyst- wall. The 
 bladder collapses in consequence of the loss of the fluid. It shrivels 
 
 1 Westphal's case of an intracranial EcMnococcus, from which the patient recovered 
 (Berliner klin. Wochemchr. , No. 18, 1873), is quite unique. 
 
 2 See the above cited observations of Kuhn, " Rech. sur les acdphalocystes, " and 
 Cruveilhier, " Anat. path. ge"n., M t. iii., p. 550. 
 
 3 I have seen livers of cattle in which all the Echinococci were thus changed, so that 
 one was compelled to look for the cause in the state of the affected organ. 
 
DEATH AND DEGENERATION OF THE ECHINOCOCCUS. 651 
 
 more and more, loses its former pellucid appearance, and becomes an 
 indiarubber-like substance, which finally (though perhaps after a con- 
 siderable time) degenerates into an amorphous detritus. The tumour, 
 of course, decreases in size as the fluid is absorbed. This may take 
 place so thoroughly that only a small knot remains where there 
 formerly existed a conspicuous Echinococcus. 
 
 Sometimes during this change a large quantity of lime, especially 
 of the carbonate, is deposited in the former granular layer, so that the 
 latter can not only be removed from the substance of the surrounding 
 organ as a connected mass, but even presents considerable resistance 
 to the knife. Berthold examined the calcareous shell of such an 
 Echinococcus from the lung of an old dromedary, and distinguished 
 on section two layers, one over the other. Of these, the outer and 
 firmer was composed mostly of phosphate; the inner, on the other 
 hand, of carbonate of lime. In the latter there were here and there 
 massive deposits of lime of a distinctly crystalline character. 1 
 
 The changes here described have been in part already observed by 
 the older anatomists, though their true nature was not recognised. 2 
 Starting from the supposition that the Echinococci were of the nature 
 of tumours, it was thought that transitions might be traced from the 
 hydatids sometimes into tubercles (Morgagni), sometimes also into 
 atheromata, steatomata, melicerida (Ruysch). Even the demonstration 
 that the Echinococci were animals allied to the bladder-worms has 
 not quite dismissed the old idea, for even in 1819 the attempt was 
 made to deduce from them not only tubercular deposits, but also 
 scirrhus and other neoplastic formations. 3 
 
 It requires no special mention that the many and serious dis- 
 turbances induced by the Echinococcus suggested their association 
 with dangerous tumours ; and that all the more, since the life-history 
 and development of the parasite exhibits various phases, the zoological 
 nature of which is difficult to determine. I recall, for instance, the 
 existence of the so-called " secondary " hydatids, and further, that 
 the power of movement, which was usually regarded as one of the 
 most important attributes of animal life, seemed here wholly absent. 
 
 The medical public has but slowly and reluctantly acknowledged 
 the true nature of this parasite ; and even when no one doubted that 
 the Echinococcus, and particularly the hydatid Echinococcus, was in 
 
 1 GottingiscJie gelehrte Anzeigcn, p. 1975, 1837. 
 
 2 See Kiichenmeister's results, Deutsh. Archiv f. Gesch. d. Med., Bd. ii. u. iii. 
 
 3 Baron, " An Enquiry illustrating the Nature of Tuberculated Accretions and the 
 Origin of Tubercles:" London, 1819; and a subsequent paper, "Illustrations of the 
 Enquiry respecting Tuberculous Diseases : " London, 1822. One must note that Baron 
 used " hydatid " in the wide sense of the old physicians, and made it include more than 
 the Echinococci. 
 
652 
 
 ORDINARY TAPE-WORMS (CYSTOIDEl). 
 
 truth an animal, and the young stage of a tape-worm, yet the multi- 
 locular form was still regarded as a tumour. Now, however, this error 
 has been dissipated, and our knowledge of this important parasite has 
 attained a fairly satisfactory completeness and certainty. 
 
 DIVISION II. Ordinary Tape-Worms (Cystoidei). 
 
 As we have already noted (p. 360 and p. 400), this group includes 
 all those Tcenice which are not cystic tape-worms. They do not, how- 
 ever, form a single well-defined group, but rather include many diverse 
 types. They are distinguished from the cystic tape-worms by the 
 manner of their development, i.e., by the absence of a proper bladder- 
 worm stage. They possess, indeed, usually a larval stage somewhat 
 resembling the bladder-worm, but this is so small, and its bladder is 
 so little developed, that in spite of the resemblance the term " bladder- 
 worm " is hardly applicable. Strictly speaking, the embryonic body 
 of this young stage (Cysticercoid) cannot be regarded as the bladder, 
 since it is solid, and has not that accumulated fluid which suggested 
 the theory that the true bladder-worm was a dropsical degeneration. 
 
 The " bladder " is, however, usually distinctly marked off from the 
 
 Fio. 336. Cysticercus arionis, with (A) retracted 
 and (B) evaginated head. ( x 50.) 
 
 FIG. 337. Cysticercus gtomeridis, 
 after Villot. (x 50.) 
 
 rest of the tape-worm body, and is, even in the extended state, recog- 
 nisable as a distinct structure. It possesses a more or less firm, some- 
 
DEVELOPMENT OF THE HEAD IN THE CYSTICERCOIDS. 
 
 653 
 
 times finely streaked cuticle, on which in some cases the embryonic 
 hooks still lie, and under which there is a finely cellular parenchyma, 
 often penetrated by numerous fat globules. Since it is contractile, it 
 probably contains muscle-fibres. Calcareous corpuscles are, it seems, 
 found only in the appended head-process. Similarly, the ramifications 
 of the vessels appear to be exclusively confined to the latter, although 
 the longitudinal stems are seen to traverse the bladder, and to open 
 by a foramen at the lower end. 
 
 In contrast to these common forms of Cysticercoid, there are 
 others in which the sac-like outer body in appearance and structure 
 resembles a simple continuation of the head-bearing anterior body, to 
 which it stands almost in the same relation as the posterior portion of 
 the JHchinococcns-head. to the anterior end, which bears the attaching 
 apparatus. We have already (p. 364) noticed this formation, especially 
 in the Cysticercoids of Tcenia cucumerina, and have attempted to 
 show that this outer body was, in spite of its divergent structure, still 
 nothing but the caudal bladder, i.e., the first developmental product 
 of the six-hooked embryo. The morphological individuality (p. 386) 
 has indeed been lost ; head and caudal bladder appear as a unit, whose 
 development presents rather the appearance of a metamorphosis than 
 of an alternation of generations. 
 
 FIG. 338. Cysticercoid 
 of Tcenia cucumerina. 
 (x 60.) 
 
 FIG. 339. Young form of Tcenia torulosa(t) 
 in Cyclops serrulatus, after Gruber. ( x 25.) 
 
 This is perhaps yet more distinct in the Cysticercoids from the 
 Cyclops discovered by Gruber, where the head is always protruded, 
 instead of being retracted into the posterior body, the characteristic 
 form of the bladder-worm being thus disguised. 
 
 As in the development of the caudal bladder, so in the position of 
 the head there are manifold differences, and that even when we leave 
 those with free head out of account, and confine ourselves to those 
 species in which the head is retracted into the body. 
 
654 ORDINARY TAPE-WORMS (CYSTOIDEl). 
 
 Among these there are first of all some species in which the head 
 has exactly the same position that we have described in the cystic 
 tape-worms as primary and normal. The head is completely invagi- 
 nated, so that the subsequent external surface forms the inner lining 
 of a pouch hanging down as a process in the axis of the bladder. 
 The hook-apparatus is found at the deepest part of the pouch. This 
 is not only the case in the young stage of Tcenia cucumerina (Fig. 338), 
 which in the structure of its posterior body is especially connected 
 with the Cysticercoids of the Cyclops; but so it is also in the so-called 
 Gyporhynchus of the tench (p. 364), which possesses a distinct caudal 
 bladder, although its head-end is sometimes protruded therefrom, and 
 used for creeping about in the host, just as do the larvae of the Tcenia 
 found in Cyclops. This slight difference is noticeable, that in the 
 Cysticercoids there is never the development of a vermiform body 
 intercalated as a long neck between head and bladder, as is seen so 
 frequently, and often so strikingly, in the true Cysticerci, especially in 
 C. fasciolaris. 
 
 If our conception of the developmental history of the Cysticercoids 
 be correct (see p. 362), then the head has always at first the position 
 here described. The attaching apparatus is of course always formed 
 inside a bladder (the enlarged six-hooked embryo), the first rudiment 
 of the head appears as a hollow bud, which often at an early stage 
 exhibits an elevation at its base, which grows ever further outwards 
 until the head attains its final structure, and shows inside the dis- 
 tended sac-like neck exactly the subsequent position of the tape-worm 
 head. Since, so far as we know, it is especially the species with 
 extended rostellum, e.g., Cysticercus arionis (Fig. 336), which exhibit 
 this formation, we may suppose that the elevation of the head is 
 determined by the outgrowth of this structure, and that the position 
 of the head above noted has therefore only a secondary importance. 
 
 As to the development of the Cysticercoids, I must refer to what 
 I have already said (pp. 360-368). This may again be specially 
 mentioned, that there are among them some forms which appear as 
 many -headed and racemose bladder-worms analogous to Ccenurus and 
 Echinococcus. 
 
 As yet we know but few Cysticercoids, so few that one sometimes 
 still hears the doubt expressed whether all the hundreds of known 
 Tcenice have, indeed, passed through a Cysticercoid stage. We have 
 already referred to the difficulties attending the search for Cysticer- 
 coids (p. 379, Note), and can only further answer that until the 
 demonstration of a direct development our positive experimental results 
 must be held as decisive, and they all prove the existence of an inter- 
 mediate Cysticercoid stage. 
 
CHARACTERISTICS OF THE CYSTICERCOIDS. 655 
 
 If we leave out of account the Cysticerci (p. 343) found in the 
 parenchymatous tissue of birds (Piestocystis, Dies.), which in many 
 respects connect the ordinary bladder- worms with those now under 
 discussion, we may say that only cold-blooded animals harbour the 
 Cysticercoids. The majority occur in the Arthropoda, and especially 
 in insects, but also in fish, worms, and snails. In marine animals the 
 Cysticercoids are extremely rare ; we know as yet only a single form 
 (from a Pteropod), but this readily harmonises with the fact that 
 the adult Tseniadae occur very rarely in marine animals. The great 
 majority inhabit terrestrial and fresh water animals, especially birds 
 and mammals, and chiefly those which feed on insects arid vegetable 
 food. Both classes of animals get their parasites from their food, the 
 one by directly eating the intermediate hosts, the other by the 
 accidental swallowing of the same. Man, mostly in his youth, may 
 be infected in either of these ways. 
 
 We have already noted the numerous variations in the external 
 appearance and internal structure of the Cysticercoid tape-worms. 
 We find among them species with many, and species with few joints, 
 some small and short, others long and broad, some, indeed, the longest 
 tape- worms we know, 1 some armed, others hookless. In many of the 
 latter the head is as large as, or even larger than, that of Tcenia 
 saginata, while others, especially among the armed forms, are less 
 developed in this respect. Similarly the hooks show in number, size, 
 and arrangement the most manifold variations, much more striking 
 than in the cystic worms. Generally the development of the attaching 
 apparatus is less powerful. With, too, this agrees the formation 
 of the rostellum, whose muscular walls enclose a spacious cavity, 
 which is all the more striking since the early lenticular form has 
 been exchanged for an ovoid or cylindrical one. In the last instance 
 the apex often forms on the protrusion of the rostellum a more or less 
 long and lank proboscidiform projection. 
 
 The adult proglottides are usually short, much shorter, indeed, 
 than they are broad, and are more firmly connected with one 
 another than in the cystic tape-worms, so that in expulsion long 
 stretches rather than single joints are set free. The uterus has 
 usually the form of a wide cavity with more or less numerous boss- 
 like or pouch-like diverticula. Here and there we find the dendritic 
 ramifications of the larger cystic tape-worms, with this difference, 
 however, that the main stem has, in correspondence with the shape of 
 the joints, a transverse instead of a longitudinal course. In other 
 cases the diverticula become isolated as they are filled with eggs 
 
 1 The Tcenia expansa of the ruminants is sometimes, according to Goze and others, 
 over 100 feet long. It has generative pores on both sides like Dipylidium. 
 
656 ORDINARY TAPE- WORMS (CYSTOIDEl). 
 
 and form small independent brood-pouches, filling the middle layer 
 of the joint, varying in number and arrangement. The structure of 
 the germ -producing organs exhibits also numerous variations, which 
 are in part so fundamental and characteristic that various attempts 
 have been made to utilise them for systematic purposes. We have 
 already noted many of these peculiarities, but we may shortly revert 
 to them. Sometimes the female reproductive organs recall exactly 
 the structure of the cystic tape- worms, while the testes are but 
 sparsely developed, being, indeed, sometimes reduced to two or three. 
 On the other hand, the male and female spermatic reservoirs and the 
 cirrhus often attain a considerable size. The generative openings 
 usually lie all on the same margin, but are occasionally found on 
 both sides. The eggs have besides the thin light-brown shell, and 
 the very constantly persistent vitelline membrane, not unfrequently a 
 third middle envelope. Where the uterine cavity is broken up into 
 distinct brood-pouches, as is the case in the Cystoidei of man, then 
 all the contained eggs of the latter are during the formation of the 
 embryos united into a single mass, which is in some respects com- 
 parable with the cocoon of the leech or earth-worm. The embryonic 
 hooks are often of considerable size, and are in some cases larger than 
 the hooks of the adult worms. 
 
 We cannot yet determine with certainty how many human tape- 
 worms belong to this group. As yet we only know four, but these 
 have all been lately discovered, and the number will doubtless be yet 
 increased. This is the more probable, since, with one exception, these 
 worms belong to foreign countries, where helminthology has been little 
 prosecuted, and where the mode of life and nutrition of the inhabitants 
 is in many respects favourable to the importation of Cysticercoids. 
 
 To all appearance, then, the number of cysticercoid Teenies in man 
 is larger than that of the cystic tape-worms ; but none of the former 
 can be compared to the latter in distribution, frequency, or clinical 
 importance. It seems even doubtful whether any one of them is 
 peculiar to man. The species indigenous in our country, 1 Tcenia 
 cucumerina, is certainly not, for it is usually found in the dog and 
 cat, and only occasionally in children. 
 
 According to their natural relationship these worms belong to 
 various groups, the members of which are probably in every case con- 
 fined to the Mammalia. 
 
 1 We must leave it as undecided whether the smooth-shelled T&nia-eggs found by 
 Ransom in the faeces of a child belong to a second European species (Medical Times, 
 vol. x., p. 598, 1856). The same must be said of Heller's report, according to which the 
 Erlangen Pathological Institute contains a Tcenia as yet unidentified, which was voided 
 by a child (Zieinssen's " Handb. d. sp. Path. u. Ther.," Bd. vii., p. 560) ; Eng. transl., 
 vol. vii., p. 670. 
 
DEFINITION OF T^INIA NANA. 
 
 657 
 
 GROUP A. Head small, with a single circle of small hooks, seated on 
 an ovoid rostellum. Joints short and broad, even when mature. Genera- 
 tive openings on one side, testes few, a small recep- 
 taculum on the short vagina. Cirrhus-pouch 
 poorly developed. The uterus, a wide cavity ex- 
 tending across the whole joint, and with irregular 
 diverticula. The eggs have two smooth shells, and 
 contain an embryo with somewhat large hooks. 
 
 Subgenus Hymenolepis, Weinland. 
 
 The various species are usually short, and 
 are most commonly found in insectivorous 
 animals. 
 
 Other related forms, usually from herbi- 
 vorous animals, are specially distinguished by 
 the absence of hooks, and by the considerable 
 length of the jointed body. 
 
 Taenia nana, von Siebold. 
 
 Von Siebold und Bilharz, " Zur Helminthographia hu- 
 m&na,,'Zeitschr.f. wiss. Zool., Bd. iv., p. 64, Tab. v., Fig. 18. 
 
 A small tape-worm, from 12 to 20 mm. long, 
 and with a maximum breadth of 0'5 mm. In the 
 anterior third the body is thread-like, but pos- 
 teriorly it enlarges somewhat quickly, so that the 
 last third has an almost uniform breadth. The 
 spherical head has a diameter of about 0*3 mm., 
 and bears, besides the four round suckers (O'l mm.}, 
 a rostellum of O06 mm., whose anterior truncated 
 portion has a single circle of from twenty-two to 
 twenty-eight extremely small hooks. The member 
 of segments amounts to 150-170, of which the 
 last contain thirty or more ripe eggs. The length 
 of the joints is insignificant, and at the posterior 
 end of the worm hardly amounts to quarter of 
 the breadth. The uterus corresponds in form to 
 the joints, and contains numerous eggs of 0*04 mm. 
 in diameter, with embryos of 0'023 mm. 
 
 FIG. 340. Tcenia nana. 
 (x 18.) 
 
 The tape-worm which is here shortly described was discovered by 
 Bilharz in Egypt, and although hitherto observed only in a single 
 
 2 T 
 
658 
 
 DESCRIPTION OF TJEXIA NANA. 
 
 case of a boy who had died from meningitis, it was in this instance 
 found in countless numbers in the duodenum. 1 We owe our know- 
 ledge of it to v. Siebold, who has published the communications made 
 
 to him by Bilharz, along with a drawing 
 of the anterior end of the body, in the 
 above-quoted memoir. But as we have 
 already mentioned in another connec- 
 tion, the account is unfortunately very 
 insufficient, so that it would be difficult 
 to recognise the worm from it. All the 
 more do I rejoice that in the above 
 diagnosis, and the following statements, 
 I am able to offer the results of an inde- 
 pendent investigation. The specimens 
 which were placed at my disposal came 
 from Bilharz himself. I received them 
 FIG. 341. Head of Tanianana, through the kindness of Professor Glaus 
 with retracted rosteiium (x loo). from Dr Markusen, and partly also from 
 
 (A.) An isolated hook (x 600). TTM t 
 
 Professor Welcker in Halle, who most 
 
 willingly sent me a number of duplicates from the collection of Egyptian 
 Helminths presented by Bilharz to the Anatomical Museum in Halle. 
 In the largest of my specimens the length of the worm is 15 mm. 
 (Bilharz mentions one of six and the other of ten lines in length.) 
 The head is almost one-half larger than the adjacent neck, whose 
 separate joints can only be distinguished at some distance. I always 
 found the rosteiium in a retracted condition. The hooks consist, just 
 as in the cystic tape-worms, of a claw and two roots, of which the 
 anterior one is very thick, and the posterior more slender, as is also 
 often the case in other Cysticercoid Tcenice.* The claw is slender, 
 and has a sharp point, by which it is easily distinguished from the 
 equally long anterior root. 3 All the hooks are of exactly the same 
 
 1 Spooner indeed thinks that he has observed T. nana in America (A mer. Journ. Med. 
 Sci., Jan. 1873), and that in a young man, who, in consequence of the worm, exhibited 
 symptoms quite similar to those caused by the presence of a large-jointed tape-worm. 
 But the diagnosis appears somewhat uncertain and suspicious. Perhaps the parasite be- 
 longed to the following species, which, as we shall see, is indigenous to America. 
 [Hellich has recently obtained T. nana in numbers from a girl seven years of age in 
 Belgrade. I have had the opportunity of examining some of these specimens, and thus 
 not only of confirming the diagnosis, but also of correcting some of my former statements 
 regarding the species. R. L.] 
 
 2 Bilharz's expression " hamuli bifidi " (v. Siebold, loc. cit. ) is probably due to his er- 
 roneous interpretation of this anterior root-process as a second claw. 
 
 8 This is the case not only in the related tape-worms of our mice and shrews, but 
 also in Stem's Cysticercoid from Tenebrio, and in a number of Teenies from birds ; regard- 
 ing the latter see Krabbe, " Bidrag til Kundskab om Fuglenes Bandelorme," Tab. viii., 
 ix., Kjobeuhavn, 1869. 
 
DEVELOPMENT OF T^NIA NANA. 
 
 659 
 
 form and size. The latter is, however, very insignificant, and is even 
 less than in Tcenia echinococcus, for according to my measurements 
 the total length does not amount to more than O018 mm. The dis- 
 tance between the two roots is O015 mm., and that between the end 
 of the anterior root and the point of the claw 0*0076 mm. 1 
 
 Soon after the appearance of the segmentation one notices in the 
 centre of the individual segments a bilobed accumulation of dark 
 granules, which become more abundant and distinct posteriorly, and 
 
 FIG. 342. Proglottides of Tcenia nana ( x 100). (A.) With female 
 genital glands; (.) With formation of eggs commencing; (C.) In 
 mature condition. 
 
 gradually assume more definite forms. In addition to these there 
 appears after a time a sharply defined club-shaped organ, which, near 
 the anterior border, runs through the joint in a transverse direction, 
 and sometimes projects with its rounded and thickened end as far as 
 the middle of the latter. In the interior of this club there is a cylin- 
 drical passage, the end of which is enlarged into a spherical cavity. 
 
 There can be no doubt that this structure is part of the male 
 organs, and performs the functions of a cirrhus or cirrhus-pouch ; in- 
 deed, I have sometimes seen its point protruding for a short distance 
 beyond the sharp border of the joint. 
 
 [In the drawing (Fig. 341, A) the posterior root ia represented as too short ; it 
 should be twice as long. R. L.] 
 
C60 DESCRIPTION OF T^NIA NAN A. 
 
 Further, the nearer the joints approach the middle of the body, 
 the more does the above-mentioned granular mass assume the appear- 
 ance of a number of closely packed lobes. The latter are grouped 
 together into an irregular, two-lobed figure, the parts of which are 
 distributed over the two lateral portions of the joint. Close behind 
 the mass there is observed another structure of a more finely granular 
 nature which I have recognised as the yolk -gland, while the organ 
 lying above it represents the two ovaries. The testes are three in 
 number, and situated near the posterior border of the segment. 
 
 In the joints of the middle of the body a new structure appears 
 behind the cirrhus- pouch, which, on account of the increasing 
 breadth of the segments, has in the meantime drawn nearer and 
 nearer to the side. It is a body of a pear-like form, which has 
 an almost fatty and shining appearance, and at first sight might be 
 interpreted as a vesicula seminalis. And, indeed, the contents of this 
 body consist of seminal filaments, closely aggregated into an almost 
 homogeneous mass; nevertheless I am quite convinced by the ex- 
 amination, not only of Tcenia nana., but also of the related forms 1 
 that it is not a vesicula seminalis, but a receptaculum seminis. 
 It is filled by means of a short vagina, which opens beside rather 
 than under the cirrhus-pouch, and consequently can but rarely 
 be observed with perfect distinctness. As the filling proceeds, the 
 female genital organs become gradually more shrivelled and blanched, 
 while, on the other hand, the uterus becomes distended with numerous 
 corpuscles, which can soon after be recognised as eggs. The move 
 these develop, the more does the receptacle lose its former refractive 
 power. It becomes paler and smaller, and, along with the cirrhus- 
 pouch, gradually retires in an anterior direction before the pressure 
 of the uterus, until it comes to lie close to the anterior border, 
 where it is easily overlooked. 
 
 I must contradict the statement of Bilharz, that the eggs of Tcenia 
 nana possess a " thick and yellowish " shell. As I have remarked 
 above, I can clearly distinguish two thin and clear, but 
 somewhat firm egg-shells, which are widely separated 
 from each other. The six hooks could be but rarely 
 perceived in the coarsely granular embryonic substance, 
 but in several instances they were discovered in the 
 form of little rods, 0*0095 mm. in length, with bent, 
 
 FIG. 343. 
 
 Ripe egg of sickle-shaped points. 
 
 T&nia rwna, Only a few calcareous corpuscles of insignificant size 
 
 (x250.) ' were distributed through the parenchyma of the body. 
 
 1 If taken in connection with the foregoing observations by Stieda, Feuereisen, and 
 Steudener, iny communications supply a somewhat complete picture of the structure of the 
 
DEFINITION OF TCENIA FLAVO-PUNCTATA. 
 
 6G1 
 
 Eegarding the origin of the worm, we are at present unable to give 
 any authoritative decision, and we shall therefore content ourselves 
 with the supposition that, as in the most nearly related species, the 
 worm passes its youth as a Cysticercoid in some insect or snail. The 
 large numbers of the worms by no means contradict this supposition, 
 since, in order to account for them, there is no need of assuming a 
 repeated transmission ; on the contrary, they may be quite sufficiently 
 explained by the observations of Villot regarding the Cysticercoids of 
 Glomeris (p. 367), which, like the Cysticercoids of Stein, from Tenebrio, 
 belong to this group. 
 
 Klichenmeister's attempt to rank the worm along with Tcenia 
 echinococcus is altogether excluded by its organization. 
 
 Taenia flavo-punctata, Weinland. 
 
 Weinland, "Essay on the Tape-Worms of Man," Cambridge, U.S.A., 1858, p. 49. 
 Weinland, " Beschreibung zweier neuer Taenioiden aus dem Menschen," Nova Acta 
 Acad. Cces. Leop.-Carol., t. xxviii., pp. 8-12, tab. iv., 1861. 
 
 This tape-worm, which has hitherto been only once observed* and 
 described, attains the length of about a foot. The anterior half of the 
 body consists of unripe joints, 0*2 to 0*5 mm. long, 
 and from 1 to 1'25 mm. broad, each of which 
 exhibits posteriorly a central yellow spot of some- 
 what large size. This is the distended receptaculum 
 seminis (Weinland *s testis). In the second half 
 the joints attain a length of 1 mm., and a breadth 
 of 2 to 2'3 mm. They have lost the yellow spot, 
 and owing to the abundant development of eggs, 
 have assumed instead a brownish-grey colour. 
 The eggs are surrounded by a smooth double 
 envelope, and are about 0'06 mm. in size. The 
 uterus is a simple wide cavity, vjhich occupies 
 almost the whole segment. The form of the 
 hindermost joints is trapezoidal, with a more or 
 less narrow anterior border, or sometimes almost 
 triangular. The nature of the head is un- 
 known, (?) but it was probably armed with a 
 single row of small TiooTcs- 
 
 FIG. 344. Tcenia flavo- 
 fctlto). 
 
 sexual organs of Tcenia nana. In most points the reconstruction would closely correspond 
 with the drawing given by Feuereisen of the sexual apparatus of Tcenia setigera (see Fig. 160). 
 
 1 [Since the above was written, this worm has been observed in America by Leidy 
 (Proc. Acad. Nat. Sci. Philad., p. 137, 1884), and the same or a closely allied species in 
 North Italy by Parona (Giorn. R. Acad. Med. Torino, fasc. 2, 1884) ; on both occasions 
 the host was a child. E, L. ] 
 
 2 [The worm observed by Parona had a club-shaped head, without hooks or rostellum, 
 R. L.] 
 
662 DESCRIPTION OF MNIA FLAVO-PUXCTATA. 
 
 I borrow the foregoing diagnosis (with the exception of some 
 insignificant details) from the description given by Weinland (loc. 
 cit?) of some worms bequeathed by Dr. Ezra Palmer to the Museum 
 of the Society for Medical Improvement in Boston, Mass. The 
 specimens had been determined as BothriocepJialus, and preserved 
 in spirit. The six longer specimens, investigated by Weinland, 
 measured altogether about three feet, and were voided by an otherwise 
 healthy child, that had been weaned about six months before, without 
 any suspicion being entertained of the presence of the parasite. 
 
 At my request, Dr. Weinland was kind enough to send me for 
 investigation about an inch of this tape- worm. This portion was from 
 the middle of the worm, and exhibited hardly anything else than a 
 countless number of eggs, which filled the whole interior of the joints, 
 with the exception of the clear, thin, enveloping wall. The only 
 
 thing else that could be dis- 
 tinguished was a clear, club- 
 shaped organ, occupying a 
 transverse position upon the 
 anterior border of the joints, 
 and the rounded end of which 
 extended about as far as the 
 middle line of the worm, but 
 the other was continued into a 
 thin canal, which ran towards 
 the adjacent lateral border, 
 and there terminated in a dis- 
 FIG. 345. Ripe proglottides of Tania flavo- tinct opening. The analogy 
 
 punctata, one barren. ( x Qf ^^ ^^ ^ ^ ^^ 
 
 forms enabled me to recognise in this structure the vagina with the 
 large receptaculum seminis. The cirrhus-pouch eluded observation, 
 but whether on account of the opacity of the preparation, or because 
 of its complete disappearance, I cannot decide ; very probably it is of 
 small size. There are, moreover, so many resemblances between 
 Weinland's species and Tcenia nana, not only in regard to the 
 formation of the vagina, but in other respects, that I have not the 
 slightest doubt of their near relationship. The formation of the eggs 
 is also the same, with the exception, indeed, of the difference in size, 
 which is in favour of the North American species. Weinland 
 certainly describes three egg-membranes in his species, but, in spite of 
 careful investigation, I have been unable to distinguish more than two, 
 which are identical with the inner and outer ones of Weinland. The 
 thin, middle membrane, which is said to cling closely to the former, 
 and to be always wrinkled in the preserved specimens, I have never 
 
DEFINITION OF T^ENIA MADAGASCARIENSIS. 663 
 
 been able to find. Indeed, I am almost inclined to think that 
 Weinland has been misled by the coagulation of the not unfrequently 
 granular mass, lying between the widely separated inner and outer 
 shells. The embryo measures almost 0'03 mm., and after the applica- 
 tion of alkalis distinctly exhibits its six hooks (O'OIT mm. in length). 
 
 Among the segments which I examined there was one which, even 
 on cursory observation, attracted attention by its pale appearance 
 and small size, and especially by its narrowness. On microscopic 
 examination it proved to be without eggs, and had apparently, from 
 some unknown cause, never formed any. The receptaculum, with its 
 efferent canal, was more distinct than in the fertile proglottides, and 
 also of a larger size, unquestionably because the material had not 
 been expended otherwise. If I remember aright, the friendly donor 
 himself called my attention to this joint, with the remark that he 
 had repeatedly observed similar sterile proglottides in his Tcenia fiavo- 
 punctata.'*- 
 
 The calcareous corpuscles are in this species also small and scanty. 
 
 GROUP B. As in Hymenolepis, the sexual apertures are unilateral, 
 and the eggs provided with two smooth envelopes, and, instead of being 
 isolated, enclosed in a group within a firm enveloping substance, which is 
 continued exteriorly by a felt-like fibrous tissue. Head ? 
 
 Subgenus ? 
 
 Taenia Madagascariensis, Davaine. 
 
 Davaine, " Notesur une nouvelle espece de t&iia, recueillie a Mayotte," Archives de 
 m6dedne navale, t. xiii., 1870. 
 
 Davaine, "Traite des Entozoaires," second edition, p. 922 ; or Mem. Soc. biol., 1870. 
 
 A Tasnia of probably about 8 cm. in length, and with about 100 
 somewhat broad joints, which are at first short, but gradually assume an 
 almost square form, measuring in length and toeadth about 2*6 mm. 
 In the interior of these joints there are a large number of small bodies of 
 oval form (0*9 mm. long and 0'6 mm. broad), which are arranged in 
 transverse rows, alternating with each other, but without touching at any 
 point. Their number in each proglottis amounts to from 1 2 to 1 5 0. These 
 are not eggs, as might have been supposed, but balls of eggs, covered exter- 
 nally by a spongy substance of somewhat considerable thickness, in the 
 form of a clear sphere (of 0*5 or 0*3 mm.). The eggs themselves always 
 measure 0'04 mm. (the inner egg-shell 0'02, and the embryo 0'015 mm.), 
 and the number found in each ball is about 300 to 400. In favourable 
 
 In two communications which have appeared since these words were written (Nova 
 A eta A cad. Cas. Leop. -Carol., loc. cit.) Weinland has himself described this abnormality. 
 Similar sterile joints are occasionally found in other tape-worms. 
 
664 DESCRIPTION OF T^NIA MADAGASCARIENSIS. 
 
 objects the embryonic hooks appear in the form of fine rods. Regarding 
 the structure of the head and the anterior part ef the body unfortunately 
 nothing is known. The smallest joints hitherto observed had a breadth 
 of 2'2, and a length of 0*8 mm. 
 
 We owe the discovery of this worm to Dr. Grenet, head of the 
 French Medical Department in Mayotte, an island on the coast of 
 Madagascar, who expelled it by means of castor-oil from a boy of six- 
 teen months old, and also from a girl two years of age, who had settled 
 in the island only two months before. In both cases the children 
 were suddenly and without any assignable cause attacked with con- 
 vulsions, which ceased after the use of the anthelminthic. The first 
 patient voided, in consequence of the latter, no fewer than nine, and 
 the other two worms, which unfortunately have only reached Europe 
 in fragments. The largest of these, which was given to Davaine for 
 investigation, contained seventy-five segments. Two other shorter 
 ones exhibited seventeen and eighteen ; and there were further three 
 pieces with two joints each. All of these originated from the first 
 of the two young patients, while from the second there was only 
 received one chain with fifteen ripe proglottides. According to 
 Grenet, the latter possess, in their isolated state, great contractility, 
 and crawl about nimbly upon the faeces, with pronounced changes 
 of form. 
 
 What Davaine has communicated regarding the reproductive 
 organs of this species shows that, except as regards the egg-capsules, 
 they essentially correspond with the ordinary forms. The most 
 anterior segments exhibit no recognisable reproductive organs, being as 
 yet sexually undifferentiated (" neutre") ; and the succeeding ones have 
 at first their male organs chiefly developed. The vas deferens and 
 penis could be distinctly observed. The letter is described as a smooth, 
 short, and somewhat stout cylinder (with a diameter of 0*025 mm.) 
 protruding as much as 0'04 mm. out of an opening situated in the 
 centre of one of the lateral borders. The vagina, whose course can be 
 distinctly followed, also terminates as usual in this opening. As we 
 have already mentioned, in giving the characters of the group, the 
 pores are all found on the same lateral border. 
 
 The feature which is most characteristic of this worm, and which 
 obviates any doubt as to its specific nature, is, as we also previously 
 observed, the structure and nature of the egg-balls. To the naked 
 eye the latter appear in the form of small points, which become 
 visible as soon as the proglottides are 1 mm. in length. From the 
 structure which they exhibit when placed under the microscope, Grenet 
 has compared them to the cocoons of the leech. Since we have learned 
 
DEFINITION OF T7ENIA CUCUMEEINA. 665 
 
 from Davaine that these bodies are not separate eggs, as Grenet sup- 
 posed, but masses of eggs, which are embedded in and enveloped by 
 a common cementing substance of a firm (apparently chitinous) nature, 
 this comparison is all the more apt ; and, moreover, the cementing 
 substance, just as in the leech, is continued externally into a fibrous 
 tissue, the principal stems of which assume a radial direction, fre- 
 quently anastomosing and uniting to form a spongy coating. Between 
 the ramifications there are a few calcareous corpuscles, which are 
 indeed sparsely distributed over the whole parenchyma of the body. 
 
 In some respects this spongy coating recalls the border of rods in 
 the egg-shell of the cystic tape- worms. Like the latter, it increases 
 the vitality of the egg, and probably also serves to preserve it from 
 desiccation. 
 
 GEOUP C. The proglottides have two peripheral sexual openings 
 opposite to each other, leading to a male and female efferent apparatus, 
 the latter of which possesses, in addition to the receptaculum, a special 
 germ-gland. The proboscides are oval or spherical, and are provided 
 with a number of rows of small hooks, which, instead of roots, have a 
 discoidal base. After the development of the embryo, the eggs become 
 cemented together into rather large groups. 
 
 Subgenus Dipylidiiim, Leuckart. 
 
 w 
 
 FIG. 346. Head of Tcenia cucumerina, with rostellum and hooks, in different 
 stages of contraction. ( x 140.) 
 
 A small group of tape-worms, which, according to the definition 
 just given, includes only a single species parasitic in the cat and the 
 dog, but which would be considerably increased were we to regard 
 only the presence of two peripheral pori. 
 
 Taenia cucumerina, Eudolphi. 
 (Incl. Taenia elliptica, Batsch.) 
 
 In a ripe condition has usually a length of 18 to 25 cm., and in 
 the posterior joints a breadth ofl'5 to 2 mm. The anterior end of the 
 
600 
 
 DESCRIPTION OF T^ENIA CUCUMERIXA. 
 
 body is tliin (0'15 mm.) and thread-like, and provided with a head, in 
 diameter about twice as much. If the proboscis be extended, it forms 
 upon the apex of the head a club-shaped projection, usually short and 
 rounded, O'l mm. in diameter. The total number of the hooks, which 
 surround the extremity of the rostellum in four irregular rows, is 
 about 60, and of these half belong to the lowest row, which contains 
 the smallest hooks (only about 0*0057 mm. in height, and with a basal 
 disc of the same size). The largest hooks are 0*015 mm. in length, 
 and the diameter of their basal disc is about the same. 
 The posterior half of the rostellum varies in ap- 
 pearance according to the state of contraction, and 
 sometimes looks almost like a thin stalk on the 
 thickened club-shaped anterior end. The first forty 
 joints are of insignificant length and breadth. They 
 occupy the foremost 6/08 mm. of the worm. But 
 beyond that point the joints lengthen so much that 
 they ultimately become four or five times as long as 
 they are broad. In the meantime tJie breadth has 
 also considerably increased (to 2 mm.). As their 
 size increases, the joints are gradually more dis- 
 tinctly marked off from each other. The lines of con- 
 nection are constricted, and fie corners rounded off, 
 so that the posterior half of the worm assumes a more 
 and more decidedly moniliform appearance. The 
 ripe proglottides are of a red colour (on account of 
 the egg-masses shining through), and may be easily 
 detached from, tJie chain. Their number varies, according to circum- 
 stances, from ten to twenty-five, or even more. The male organs attain 
 maturity at about the forty-sixth joint. By the sixtieth joint, the 
 embryonic development is completed ; and at the seventy-fifth the first 
 distinct egg-masses may be seen (0'07 to 0*2 mm. in diameter). The latter 
 have a roundish discoidal form, and contain, according to tJieir size, a 
 variable number of eggs, on an average two to three dozen. They are formed 
 of a sharply defined firm cement of a brownish colour, and the number 
 in each joint amounts to perhaps from 350 to 400. The isolated egys 
 measure 0*05 mm., and the embryo (with hooks of 0*015 mm.) 0'033 mm. 
 
 The species which we have thus shortly described is by far the 
 most frequent tape- worm in dogs and cats, or at least in those which 
 are reared indoors. It generally lives socially, several hundred speci- 
 mens being sometimes found side by side, and in some cases as many 
 as 2000 (Krabbe). If cystic tape-worms be also present, they are 
 always situated farther forwards in the intestine. Hence the worm 
 
 FIG. 347. Tamia cucu. 
 merino, (nat. size). 
 
HISTORICAL ACCOUNT OF T^NIA CUCUMEPJNA. 667 
 
 is usually found in the hinder part of the small intestine. Since it 
 possesses a great elasticity, and can be drawn out almost like a thread 
 to three or four times its usual length, the end of the chain is often 
 found in the neighbourhood of the large intestine, in the interior of 
 which the free proglottides, which are readily recognisable from their 
 red colour and elliptical form, are usually accumulated in great 
 numbers. 
 
 Although this worm is quite as frequent in the cat as in the dog, 
 Linn4 has applied to it the name Tcenia canina, which has since been 
 changed more than once (by Pallas into T. moniliformis, and by Goze 
 into T. elliptica). Eudolphi and his followers, indeed, believed that 
 the worms found in the dog and in the cat should be distinguished as 
 two distinct species 1 (T. cucumerina and T. elliptica), and at the time 
 of the first edition of this work I was of the same opinion. But as 
 the result of renewed and careful investigation, I am now obliged to 
 agree with Goze, that it is impossible to discover any radical differ- 
 ences between them. 2 
 
 If now it be asked on what grounds this T. elliptica is included 
 among human Helminths, we may answer, in the following way : 
 
 Linne", who first recognised T. canina, as a specific form, and 
 rightly regarded the bilateral position of the sexual opening as its 
 most important character, also maintained that it was occasionally 
 found in man. 3 He even asserted that such cases were known to 
 him. But this assertion was gradually forgotten. Pallas contra- 
 dicted it, while Goze, Bloch, and Kudolphi did not deem it worthy of 
 mention. But, in spite of this, the worm deserves the place assigned 
 to it by Linne, 4 although it occurs in man only occasionally and ex- 
 ceptionally, and usually only during childhood. 
 
 In the Museum of Comparative Anatomy, in Halle, there is, among 
 other Helminths, a preparation which, according to the label written 
 by H. Meckel, contains a convoluted T. canina, Linn., which was 
 voided by a boy called Krebs during his stay in the surgical wards 
 of Blasius. Through the kindness of Professor Welcker, I have 
 
 1 Tcenia elliptica was also erroneously described as destitute of hooks. 
 
 2 The fact that in the dog Tcenia cucumerina often attains a larger size can hardly be 
 considered as a specific difference, since the same is true of Ascaris lumbricoides and of A. 
 mystax, when they occur in different hosts. Even the statement of Krabbe ("Rech. 
 helminthol. ," p. 40). that in Iceland the cat is exempt from this Tcenia, while dogs fre- 
 quently suffer from it, does not seem to me to decide the matter. 
 
 3 " Amoenit. acad.," ii., p.. 81. 
 
 4 I now perceive that my statements in the first edition of this work (p. 402) regarding 
 a Tcenia cucumerina, which Eschricht had received as voided by a Moorish slave in St. 
 Thomas, are based upon an error, since the parasite was not T. cucumerina but T. cucur- 
 bitina ( = T. solium, Auct.) (See Nova Acta Acad. Cces. Leop.-Carol., Suppl. ii., t. xix., p. 
 139. 
 
6G8 DESCRIPTION OF TVSNIA CUCUMERINA. 
 
 had an opportunity of examining these specimens, and have con- 
 vinced myself that they belong to T. citcumerina. There are, perhaps, 
 forty to fifty pieces, usually between 100 and 130 mm. in length, 
 and the majority of them still without egg-masses. Unfortunately, 
 I found it impossible to learn anything further regarding the boy 
 Krebs, so that I am unable to decide whether his illness had any 
 connection with the parasite. The supposition of an accidental mis- 
 take, or designed deception, is rendered highly improbable from the 
 circumstances under which the patient lived. 
 
 This case in Halle is, however, not the only one which I can 
 adduce. I owe a second to a communication from Dr. Weinland of 
 Frankfort, whose name I have already so often had occasion to 
 mention with gratitude. The case in question is that of a child 
 thirteen months old, who from time to time voided single proglottides 
 of small size and reddish colour, which were recognised by the attend- 
 ing physician, Dr. Salzmann, and by Weinland as proglottides of 
 Tcenia cucumerina.' 1 Through Dr. A. Schmidt of Frankfort I soon 
 afterwards became acquainted with a third case, and that, too, of a 
 child, only, however, thirteen weeks old. The mother observed a 
 portion, about six inches in length, protruding from the anus, tore it 
 off, and brought it to Dr. Kiister of Cronenberg, through whom it fell 
 into the hands of Schmidt. The head was wanting, but the nature of 
 the joints left no doubt regarding the nature of the worm. 
 
 Since the foregoing communications were published in the first 
 edition of this work, our experience of the occurrence of Tcenia cu- 
 cumerina in children has increased so much, that the cases in 
 question can no longer be regarded as specially rare. According to 
 Krabbe, the worm occurs in man in Denmark, and according to 
 Cobbold, in England, while no fewer than six cases have been brought 
 under my own notice by different physicians. 2 It was always children 
 between nine months and three years old who were infected with 
 this tape-worm. The joints generally issued singly, sometimes spon- 
 
 1 Salzmann has in the meantime himself described this case (Wurtemb. naturw. 
 Jahreshefte, p. 102, 1861 ; Froricp's Neue Notizen, iii., 9, 1861 ; Deutsche Klinik, p. 32, 
 1861). 
 
 2 I have not included among these the " proglottidcs neonati," mentioned in the first 
 edition of this work, which were observed by Kramer (Illustrirt. med. Zcitung, Bd. iii., p. 
 295), who first described them as having a strong resemblance to Tcenia cucumerina. Yet 
 I have convinced myself, by the investigation of the original specimens preserved in the 
 Pathological and Anatomical Collection at Gottingen, that they belong to this worm. 
 The statement that * ' the latter, to the amount of about a teaspoonful, were voided by a 
 newly born child about twelve hours after birth, and before it had received milk," is ex- 
 tremely incredible, and irreconcileable with our present knowledge of the life-history of 
 T. cucumerina. It is much more probable that it was voided by a dog or a cat than from 
 the child in question, which is described as perfectly healthy, and which never voided any 
 more proglottides. 
 
DISCOVERY OF THE LARVAL STAGE. 669 
 
 taneously (on one occasion through the nose), and sometimes with the 
 stools, and continued moving for a time after their expulsion. Ac- 
 cording to the communications made to me, they had a length of 5 to 
 8 mm., and a breadth of 1/5 to 2 mm., exhibited the well-known red 
 colour, and, if investigated in a fresh condition, contained the already 
 described clusters of eggs. Schoch-Bolley of Zurich, who in one case 
 succeeded in expelling entire worms by means of Kamala, while in all 
 the other cases only portions were obtained, estimates the length of 
 the worm at nearly a foot. As but two worms were voided in this 
 case, it appears that T. cucumerina does not occur usually in such 
 large numbers in man as in dogs and cats, and that in most cases 
 only a few are found living together. 
 
 So far as I know, no symptoms of disease were observed in any of 
 these cases. If a larger number of worms were present, it might per- 
 haps be otherwise. At least it has been observed that under such 
 circumstances dogs sometimes exhibit cramp and other symptoms of 
 nervous or gastric disease. I have already (p. 143, note) quoted a 
 case of this kind from Goze's famous " Naturgeschichte." A second 
 one is cited in another part of this work from the observations of 
 Wagler, 1 which, however, only differs from the former in the increased 
 gastric disturbances. 
 
 Now, however, we are not only acquainted with the fact that T. 
 cucumerina is by no means very rare in man during childhood, but 
 have also learned the way in which children are infected ; in other 
 words, an unexpected disclosure has been, made regarding the life- 
 history of the worm. 2 
 
 This discovery was made in the summer of 1868 by one of my 
 Russian students, now Professor Melnikoff, while 
 busied in my laboratory with investigations 
 regarding the embryology of the louse. He was 
 examining for the purpose the dog-louse (Tricho- 
 dectes canis), and one day discovered in the 
 body-cavity of this parasite (which, instead of 
 the piercing and sucking mouth of Pediculus, 
 is well known to possess a masticatory apparatus, 
 and to gnaw the epidermis of its host), some 
 small white bodies which he did not know how 
 to interpret. After close investigation, I recog- 
 nised them as the cysticercoid forms of Tcenia p IG . 343. Cysticer- 
 cucumerina. The rostellum and the formation c ? id of Tomia cucume- 
 
 /> , , , , i-iiiT i nna. ( x 60.) 
 
 or the hooks removed all doubt as to the 
 
 correctness of the diagnosis. Strange to say, the Cysticercoid was 
 
 1 Loc. cit., p. 324. 2 Archivf. Naturgcsch., Jahrg., xxxv., Bd. i., p. 62, 1869. 
 
670 DESCRIPTION OF TJEXIA. CUCUMERINA. 
 
 without a proper caudal bladder. It is true that the entire attaching 
 apparatus, including both suckers and rostellum, was retracted, but the 
 envelope of the latter did not differ either morphologically or histo- 
 logically from the rest of the body. The Cysticercoid appeared exactly 
 like an chinococcus-hQa,d with a retracted apex. 
 
 The intermediate host of Tcenia ciwumerina having been dis- 
 covered, 1 it occurred to us that it might be possible to rear its Cysti- 
 cercoids. A pulp, made of the ripe joints of the Tcenia, was by my 
 advice applied to a portion of skin upon which the Trichodedes were 
 plentiful, and afterwards the first stages of the worm were sought 
 for in these insects. These we succeeded in finding on several occa- 
 sions, and for the first time seven days after the commencement of 
 the experiment. They were in the form of club-shaped, six-hooked 
 embryos, which had attained a length of 0'2 mm. double their former 
 size, and lay free in the body-cavity. Eegarding their origin, there 
 could be no doubt from the six hooks still situated at the thinner end. 
 
 A comparison with the above-described Cysticercoids seems to 
 suggest that the distended end of the body in this case becomes pro- 
 vided with hooks, and is then retracted into the dependent thinner 
 part, but without the latter being formed into a special bladder-body, 
 or producing the tape-worm head by endogenous budding. I may 
 refer in this connection to the description which I have already given 
 of the mode of development of the Tcenice (p. 364). 
 
 These results reveal to us clearly and explicitly the life-history of 
 Tcenia cucumerina. The egg-capsules, which have probably been long 
 preserved from desiccation, and have retained their power of develop- 
 ment, make their way sooner or later (sometimes still enveloped by 
 the proglottides, and at other times alone) from the excreta to the 
 hairy skin of the dog, and thence to the Trichodectes living upon it, 
 in the interior of which the eggs change into Cysticercoids. It is easy 
 to see that dogs, which, like other animals, often lick themselves, and 
 also directly prey upon their vermin with their lips and teeth, often 
 find opportunities of devouring the hosts of these bladder-worms, and 
 of course the more frequently the more that their condition and mode 
 of life facilitates the transmission of the eggs, and the increase of the 
 ectoparasites. Uncleanly kept house-dogs thus exhibit a peculiarly 
 favourable combination of the conditions necessary for the develop- 
 ment of Tcenia cucumerina. 
 
 The infection of man takes place, as might be supposed, either 
 through the tongue of the dog, which returns caresses by licking, or 
 
 1 This demonstration, of course, showed that the former conjectures regarding the 
 intermediate host of Tcenia cucumeiina (see first German edition, Bd. i., p. 404) were 
 illusory. Even then, however, it seemed very likely that the latter would be an insect. 
 

 POSSIBILITY OF DIRECT DEVELOPMENT. 671 
 
 through the hands, which touch and stroke this animal. Thus in 
 both cases the transmission takes place indirectly, and this explains 
 why the tape-worm occurs in man only in small numbers, or even 
 singly. In all cases the hosts have in some way or other come into 
 close contact with the dog. Nor does it surprise us to learn that 
 these hosts are most frequently children, since they generally treat 
 dogs with the most unrestrained familiarity. 
 
 Hering, however, cannot reconcile himself to the significance 
 which the change of hosts possesses in the life-history and circulation 
 of the parasites, and is, moreover, of the opinion that the Cysticercoid 
 state is by no means necessary to the development of Tcenia cucumerina 
 (nor, indeed, to any of the other tape- worms), and that the worm may 
 be developed in the subsequent host, directly from the six-hooked 
 embryo. To test the accuracy of this supposition, he fed fourteen 
 dogs with the ripe terminal joints of T. cucumerina ,* and afterwards 
 found the tape- worm in twelve ; but the various results agree so little 
 with the stages of the experiment, and otherwise contradict each other 
 so much, thafr the only thing that can be concluded from them is the 
 great frequency of the parasite, and especially in young dogs, such as 
 Hering used (Krabbe found T. cucumerina in 87 out of 185 cases in 
 Copenhagen, or nearly half of the dogs which he examined in search 
 of Helminths). But even if these feeding experiments are not con- 
 clusive, they are by no means without interest, since they show that 
 the transformation of the Cysfcicercoid into the adult tape- worm only 
 occupies a short time. For example, a dog only thirtj^-one days old 
 was found to contain a T. cucumerina 15 inches long, and with 
 perfectly ripe proglottides. Another dog ten days old contained a 
 tape-worm 10 lines in length, with distinctly defined and already 
 oval joints. The supposition that the dog is infected more easily by 
 sucking its mother than by licking seems hardly probable from these 
 cases, for then the date of the infection must coincide with the first 
 day of life. We can therefore hardly be wrong in supposing that for 
 its development from the Cysticercoid to the ripe proglottides, T. 
 cucumerina requires about two to two and a half weeks. 
 
 In conclusion, a few remarks on the structure of the sexual organs 
 may be added. It has already been mentioned in regard to these 
 tape-worms that the genital pore, or rather the outlet of the sexual 
 organs (since the male and female ducts open near each other without 
 any special sexual cloaca) is double. One part lies on the right, and 
 the other on the left lateral margin, both being about the middle, or 
 but little behind it, as, indeed, may be observed with the naked eye, 
 
 " Beitrage zur Entwickelungsgesch. der EingeweidewUrmer," Wiirtemb. naturwiss. 
 Jahreshcftc, p. 356, 1873. 
 
672 
 
 DESCRIPTION OF 1VENIA CUCUMERINA. 
 
 even in the small joints, if they be compressed between two glass 
 plates. In the ripe joint this double outlet is connected with a coiled 
 vas deferens, and with a vagina. Before 
 reaching the middle line, the latter comes 
 downwards, and becomes united with two 
 wing-like ovaries, and with a single yolk-gland. 
 The former always consist of groups of 
 branched tubules, while the yolk - gland 
 exhibits a simple lobed structure. Between 
 the two 1 lies a bladder-like receptaculum 
 seminis, and farther down, where the sheath 
 is connected with the yolk-gland, there is a 
 shell-gland, which, as usual, is composed of a 
 group of simple stalked cells. 
 
 Occasionally one finds joints with four 
 genital openings and efferent canals. These 
 FIG. 349. Proglottides are situated in pairs opposite to each other, 
 
 of Tcenia cucumerina in a , . , , . , ,, 
 
 sexually mature state. ( x 20). and are separated by a wider space, so that 
 in spite of their but slight increase in size, it 
 
 seems most natural to regard them as double joints, which, as before, 
 in the case of Tcenia saginata (p. 450), may be ascribed to a suppression 
 of the line of demarcation. On the other hand, one sometimes finds 
 only a one-sided development of the sexual organs. 2 
 
 The first rudiments of the genital organs are observed about the 
 twentieth joint, in the form of a parenchymatous streak, which runs 
 transversely through the whole breadth of the body. The organs 
 first developed belong as usual to the male apparatus, which, in 
 addition to the cirrhus and cirrhus-pouch, consists of the much-coiled 
 vas deferens above mentioned, and of about 180 round testes, which 
 are distributed over the whole joint. 
 
 The uterus into which the eggs are transferred from the shell- 
 gland has at the time of sexual maturity the form of a network, 
 whose cords run between the testicular vesicles, and are continued 
 laterally into a number of ceecal tubes, which in many places protrude 
 beyond the longitudinal canals. As the eggs gradually accumulate in 
 the interior of the uterus, and as their size is gradually increased by 
 the development of the embryos, both these tubes and the nodes of 
 
 1 On this subject see Steudener's paper, " Untersuchungen tiber den feinern Bau der 
 Cestoden" (Abhandl. der naturf. Gesellsch. Halle y vol. xiii., 1877), which in many 
 particulars supplements my former communications. 
 
 a Salzmann has noted other abnormalities of this tape-worm. The male and female 
 openings are, he says, sometimes widely separated from each other, and the male opening 
 is occasionally wanting. Embryos with a larger number of hooks, such as those observed 
 by Salzmann, have also been found by Ramsay- Wright and myself, p. 330. 
 
STRUCTURE AND DEVELOPMENT OF THE EGG-MASSES. 673 
 
 the network are enlarged into roundish pouches. With increasing 
 size, these become more and more sharply marked off from each other, 
 and are distributed over the whole joint in place of the testes, which 
 have in the meantime gradually atrophied. When the embryos are 
 mature, the contents of these pouches are always enclosed in a com- 
 mon cementing substance, which is perhaps formed from the original 
 contents of the uterine branches, and, on becoming firm, assumes a 
 reddish-brown colour. The number of eggs adhering together is de- 
 termined by the size of the pouches. I found some clusters with only 
 eight or ten eggs (0'07 mm.), and others with seventy, or even more 
 (0'25 mm.). The flat form of the masses is explained by the fact that 
 the pouches are very closely packed, so that by mutual pressure they 
 become flattened out, usually in the direction of the transverse 
 diameter of the joint. 
 
 During the maturing of these egg-masses, not only the repro- 
 ductive organs but the layers of substance lying between the pouches 
 gradually disappear, as indeed Mehlis has remarked. In consequence 
 of this the pouches coalesce, at first in the centre, so that the joint 
 gradually becomes an almost saccular receptacle, in the interior of 
 which the eggs remain until a rupture takes place and they are 
 set free. 
 
 The calcareous corpuscles of Tcenia cucumerina are somewhat 
 numerous, although not so abundant as in the cystic tape-worms. 
 
 2U 
 
674 
 
 DEFINITION OF THE BOTHRIOCEPHALID^. 
 
 FAMILY II. BOTHRIOCEPHALID.E. 
 
 The head is egg-shaped and flattened, sometimes in the same direction 
 as the body, and then lut slightly marked off from the latter; at other 
 times in the opposite direction ; with two longitudinal, more or less deep 
 
 FIG. 350. 
 
 FIG 351. 
 
 
 FIG. 352. 
 
 
 FIG. 350. BotJiriocephalus cordatus of man (nat. size.) 
 
 FIG. 351. Free swimming embryo of Bothriocephalu8 latus. ( x 500.) 
 
 FIG. 352. Larva of a Botfiriocepkalas from the skink. ( x 20.) 
 
 suctorial grooves, which lie opposite to each other on the flat side of the 
 chain, lut are devoid of any special musculature. Similarly, the hooks, 
 
CHARACTERISTICS OF THE BOTHRIOCEPIIALIM. 675 
 
 if present at all (Trisenophorus), are without a rostellum* The segmen- 
 tation is indistinct, and sometimes altogether absent, in which case the 
 body has a very simple structure. The joints are always broader than 
 long, and in their mature state so firmly united, that they are not detached 
 singly, but in numbers. The uterus is a simple, more or less winding 
 canal, with a ventrally situated opening, through which the eggs issue after 
 the completion of the embryonic development. The reproductive organs 
 persist throughout life, and, constantly emit new products. The yolk-glands, 
 which are of considerable size, are symmetrically divided between the two 
 sides, and often distributed over the whole cuticular layer. The cirrhus 
 and vagina generally open externally, not far from the uterus, and more 
 rarely (as in Tsenia) on the border. The eggs contain a considerable 
 quantity of yolk, and possess from the first a firm shell, with an operculum 
 at one end, so that the embryo can readily find an exit. The embryo is 
 usually covered with a distinct ciliated mantle, by means of which it can 
 swim about for some time. 
 
 Except in the case of Archigetes, the development of the larva takes 
 place in an intermediate host, but in a somewhat direct way, for the 
 embryo merely elongates, and forms the subsequent suctorial grooves. 
 Sometimes it grows into a jointed tape-worm, even in its intermediate 
 host ; but as a rule this takes place only later, after the parasite has 
 migrated from its original abode into the intestine of the definitive host. 
 A true bladder-worm stage seems always wanting, but in some cases there 
 is an appendage on the posterior border of the larval body, which in 
 genetic significance corresponds to the caudal bladder of the Cysticerci. 
 
 If we are right in ascribing the highest place among the Cestodes 
 to the Tseniadse, and especially to the cystic tape-worms, the family 
 Bothriocephalidae (in the sense here defined) must be regarded, on the 
 contrary, as the lowest group. This is evident, however, not so much 
 from the anatomical structure of the several organs, as from the fact 
 that the individual! sation of the different parts composing the body 
 is upon the whole much less pronounced than in the other tape-worms, 
 and in many cases is even completely wanting. The head, which is 
 elsewhere a structure of great independence and characteristic structure, 
 is small and simple, and often hardly other than the anterior end of 
 the body provided with the attaching apparatus. Similarly, the 
 segments are usually imperfectly separated, and sometimes not marked 
 off in any way from each other, so that the segmentation is only 
 shovel by the regularly recurring sexual organs (Ligula, Triwnophorus). 
 But when, as in some cases (Caryophyllceus, Archigetes), the number of 
 these structures decreases to one, the appearance presented is entirely 
 different. In place of the polyzootic tape-worm there is a simple 
 
676 
 
 DESCRIPTION OF THE BOTHRIOCEPHALID^. 
 
 animal, in which the various organs and functions, formerly distributed 
 over different individuals, are united in one (p. 386). 
 
 The slighter individualisation of the different parts of the body 
 also finds expression in the processes of development. Instead of the 
 former features of an alternation of generations, we find in the 
 Bothriocephalidae modifications, which rather suggest a simple meta- 
 morphosis. The primary stages of development disappear, and there 
 is a corresponding diminution in the difference between the larva 
 and the adult worm. The larval form becomes like the sexually 
 mature animal, and sometimes to such a degree, that they can only be 
 distinguished by the imperfect development of the sexual organs in 
 the former. This is perhaps most striking in the Ligulidse (Schisto- 
 wphalus, Ligula), which in their intermediate hosts, the stickle-backs 
 and bleak (Leuciscus), not only grow to their full size, but form their 
 sexual organs, which develop so far that, after the transference into 
 the intestine of their definitive host (a 
 piscivorous bird), maturity is attained in 
 an exceedingly short time (p. 379). In 
 Archigdes the whole development takes 
 place in the intermediate host. So far as 
 we know (p. 378), it is the only tape-worm 
 that undergoes no change of host, and that 
 never loses the characteristics of its larval 
 life. 
 
 These are, however, mere exceptions. 
 Usually, the larval forms of the Bothrio- 
 cephalidae are easily distinguished from the 
 adult worms, not only because they are 
 destitute of reproductive organs, but also 
 because they are unsegmented (Fig. 354). 
 They possess, as a rule, a longer or shorter, 
 ribbon-like body, whose anterior end bears 
 the suctorial grooves, and is thereby re- 
 cognised as the head. 
 
 It is doubtful whether the ribbon-shaped 
 posterior part of the body is always cast off, as in the 
 Cysticerci, on the transition to the final state ; and that 
 the more, since the head of these worms hardly ever 
 attains its full development and size during the larval 
 life, but only after the transference to the alimentary 
 canal of the definitive host. 
 The Suctorial Grooves in the larval forms are often shallow and 
 indistinctly limited in comparison with the subsequent general pro- 
 
 FIG. 354. 
 Larva of .60- 
 thriocepkalus 
 ( x 55.) 
 
 FIG. 353. 
 
 Archigetes 
 
 Sieboldi. 
 
 ( x 60.) 
 
SUCTORIAL GROOVES AND MUSCULATURE. 677 
 
 minence which they afterwards attain. They exhibit also in the adult 
 many differences, both in form and size, which are for the most part 
 correlated with the structure of the head. When the latter is broad 
 the suctorial grooves are usually oval or patelliform, but when the 
 head is transversely compressed they appear as longitudinal clefts, 
 limited by projecting lips, and extending more or less deeply in- 
 wards ; often also widened internally, or even continued for some 
 distance backwards into a caecum. 
 
 During life the suctorial grooves are in constant movement, 
 sometimes drawn out, sometimes contracted, according to the changes 
 of form exhibited by the head. The lips, too, open or close according 
 to circumstances. Here and there the head may be seen retracted 
 in the body-mass. 
 
 The Musculature of the head and of the suckers is, however, much 
 simpler than that of the Tseniadas, so simple, in fact, that it can 
 without difficulty be derived from that of the body generally. 1 The 
 greater simplicity lies especially in this, that the cup-shaped muscula- 
 ture, which is so conspicuously characteristic of the suckers of the 
 Tseniadse (and also of the Tetrarhynchi, &c.), is not developed in the 
 forms now under discussion. The muscles which here supply the 
 suckers are integral parts of the general musculature of the body, 
 directly continuous with them, and only differing in their adaptation 
 to specific functions of the attaching apparatus. 
 
 The general musculature differs further from its typical disposition 
 of the Taaniadse in this, that the longitudinal fibres extend in a con- 
 tinuous strand through the whole chain, and do not of course exhibit 
 those metameric interruptions which we have described (p. 293) in 
 those Tcenice which liberate individual proglottides. 
 
 The first modification which these muscles exhibit within the head 
 consists in the loss of that distinction between the cortical and median 
 layers which is so characteristic in the other parts of the body, and 
 especially in the sexually mature joints. Longitudinal and transverse 
 fibres lose their former disposition, and are distributed, becoming at 
 the same time thinner, with some uniformity over the whole internal 
 parenchyma of the head. Even the cellular layer of the subcuticula is 
 abundantly penetrated with fine fibres. This is especially true of the 
 subcuticula of the suckers, which not only exhibits numerous sagittal 
 fibres, but is also penetrated by transverse strands. These continue 
 out to the structureless external cuticle, and pursue a course corre- 
 
 1 See in this connection Sograff's description of the structure of the head of the 
 Bothriocephalidse in the Trans. Friends of nat. hist., Moscow, voL xxiii., part 2, p. 21 
 (Russian), which is, however, incomplete after my investigations which relate especially 
 to B. latus. 
 
678 
 
 DESCRIPTION OF THE BOTHRIOCEPHALID^. 
 
 spending to the form of the head. They are not, however, stretched, 
 as in the jointed body, but are disposed in curves corresponding to 
 the concavity of the suckers. Towards the sides the fibres separate 
 in a fan-like manner, until they severally reach the external surface 
 of the head, and are there inserted. Their function is probably to 
 bring together the lateral portions of the head, which extend as sort 
 of lips beside the suctorial grooves, and thus to narrow the grooves 
 and assist fixation. 
 
 The effect of these muscles is increased by fibres, which are dis- 
 posed at right angles to the internal cavity of the grooves, and which 
 probably play the same rdle as the radial muscles in the suckers of 
 Taeniadae. In the median layer of the head, between the two grooves, 
 these fibres are stretched, as ordinary sagittal muscles, between the 
 dorsal and ventral surfaces, while they extend transversely in more or 
 less diagonal course, through the lip-like projecting lateral borders. 
 
 The longitudinal fibres exhibit a disposition which, like that of the 
 transverse strands, is conditioned by the form of the head. They are 
 not limited to the middle portion alone, but 
 traverse, in considerable numbers and in 
 closely packed groups, the lateral portions, 
 which project dorsally and ventrally, so that 
 they form in cross section an almost H -shaped 
 figure. Their contraction causes a shortening 
 of the head, and especially of the lips, in con- 
 sequence of which the latter are slackened 
 and lose their grip. The longitudinal fibres 
 are therefore to be regarded as the antagonists 
 of the other head muscles described above. 
 They are aided to some extent by fibres which 
 pertain to the convex external surface of the 
 head, and pass from one region to another 
 like tendons, with spans of varied length. 
 Although but weakly developed and few in 
 number, they are probably sufficient to approximate the margins of 
 the external surface, and thus to separate the lips of the suckers and 
 widen the grooves. 
 
 The Cutaneous Glands. In well-stained heads of Bothriocephalus 
 latus (and it is only in such that the fibrous strands here described 
 can be clearly followed) one can detect between 'the spindle-shaped 
 cells of the subcuticular layer, both in the suctorial grooves and else- 
 where, a number of intensely stained bodies of bottle-like shape (0'017 
 mm. long by O'OOS-0'01 mm. broad), which have their necks turned 
 outwards, and which sometimes allow their contents to pass out in the 
 
 FIG. 355. Transverse sec- 
 tion through the head of a 
 young Bothriocephalus latus. 
 (x 55.) 
 
NERVOUS AND EXCRETORY ORGANS. 679 
 
 form of a small drop. 1 One is at the first glance perhaps inclined to 
 regard these structures as forming an absorption-apparatus, but the im- 
 possibility of tracing their contents into the body-parenchyma leads to 
 the supposition that they are structures of a glandular nature, such as 
 occur with more or less frequency in other flat-worms. Their absence 
 in the segmented body, and the fact that they have not been as yet 
 detected among other Cestodes, can hardly be urged as an argument 
 against the above interpretation. They serve, perhaps, for the secre- 
 tion of a mucus or even viscid substance, which facilitates the 
 attachment of the worm. 
 
 The Two Nerve Cords are seen through the head with no less 
 distinctness than the muscle-fibres. They are found at that region 
 where the middle portion passes out into the side, in a position which 
 corresponds topographically to the lateral margins of the jointed body, 
 and which is especially marked in the head, since the sagittal and 
 diagonal muscle-fibres which are attached to the internal surface of 
 the grooves leave a free triangular space at this point (Fig. 355). 
 The nerve strands are seen as two roundish or kidney-shaped spots of 
 granular appearance, which gradually approach one another towards 
 the anterior end of the head, and are finally united in a loop by a 
 transverse connective. 
 
 Internally, the nerve strands are accompanied by a longitudinal 
 vessel, the cross section of which can be traced throughout the head, 
 even far forward. Besides this, there may be observed in Bothrio- 
 cephalus latus a number of fine vessels which extend below the 
 subcuticular layer of cells, and are sometimes united to each other 
 by a lateral branch. 
 
 The Excretory Apparatus of the Bothriocephalidse has, as has been 
 already noted (p. 301) by no means the well-known rope-ladder 
 disposition exhibited by the Tseniadse. Not only do the lateral stems 
 (except in the head) exhibit a reticulated disposition, the result of 
 repeated division and anastomosis, but these deeper canals are 
 associated with a superficial system of fine vessels, which also form a 
 connected network, and are distributed over the whole body. The 
 opinion was formerly held that this fine network represented the 
 proper secretory surface of the apparatus, and to this I myself 
 formerly inclined, but the researches of Pinter 2 and Fraipont 3 have 
 
 1 I describe these structures from a preparation given to me by Braun, which was 
 made from the head of a Bothriocephalus four days old, from the alimentary canal of a 
 cat. Braun also found these bodies "of doubtful import" in the B. latus of the dog 
 (" Zur Entwicklungsgesch. d. breiten Bandwurmes," Tab. ii., Fig. 16, p. 55). 
 
 2 "Unters. lib. d. Bau d. Band wurmkb'rpers, " Arb. zool. Inst. Wien, Bd. iv., 1880. 
 
 3 "Rech. s. 1'appareil excrdteur des Trematodes et des Cestodes," Archiv. d. JBiol., 
 t. i. and ii., 1880 and 1881. 
 
680 DESCRIPTION OF THE BOTHRIOCEPHALID^E. 
 
 lately led to another view of the nature of these structures. We now 
 know that in all tapeworms, and not only in the Bothriocephalidse, 
 numerous extremely fine tubules, hitherto unobserved, are attached 
 to the greater vessels, originating separately from the latter, extend- 
 ing undivided close under the surface of the body, and ending, after 
 a longer or shorter course, in a small goblet-shaped enlargement 
 (0-008 O'Ol mm. long, by 0'004 mm. broad). The opening serves 
 for the reception of large cell, rich in protoptasm, and on this is 
 seated a cilium which hangs freely into the funnel. These cells are 
 probably the proper secretory organs. They represent, according to 
 Pintner, a system of unicellular glands, whose secretion flows through 
 a more or less long, capillary, efferent duct to the tubular apparatus. 
 
 The ciliated lappets, which have been repeatedly described by 
 earlier observers (p. 302), are all to be referred to these ciliated 
 funnels. In the vessels themselves structures of this kind are never 
 present. The earlier opinion to the contrary originated in an 
 illusion, occasioned by the presence of ciliated funnels above or below 
 the vessels. 
 
 A terminal vesicle is present in the Bothriocephalidae only in the 
 young stage, before any segments have been separated off. Afterwards, 
 the longitudinal vessels seem to open independently, as is (according 
 to Pintner) the rule also in Taeniadae. There are, however, numerous 
 observations as to the presence of special marginal pores, by which 
 the longitudinal ducts open to the exterior through short transverse 
 vessels. Pintner describes such openings in Caryophyllceus and 
 Tricenophorus, and Fraipont in various Scoleces and in Bothriocephalus 
 punctatus. In the last, these "Foramina secundaria" exhibit a 
 certain degree of regularity, being usually situated in twos or at most 
 fours, at the base of the several segments. With this agrees Kiehm's 
 observation, according to which, in Schistocephcdus (as I have been 
 able also to convince myself), an excretory aperture lies on the right 
 and on the left side of every segment. 
 
 The Generative Organs exhibit peculiarities to which we have 
 already called attention (pp. 308, 317), distinguishing them clearly from 
 the Taeniadse. These peculiarities may be, for the most part, traced 
 to the fact that the uterus, instead of being closed, as in the Taeniadse, 
 opens externally by a special aperture. The presence of this uterine 
 aperture not only permits of an early liberation of the ova, but also 
 of a continued functional activity, which of course further pre- 
 supposes that the generative organs (and especially the yolk-gland) 
 possess a very considerable development, and persist throughout their 
 life in complete integrity, while in the Taeniadee they degenerate 
 after the passage of the ova into the uterus. 
 
THE GENERATIVE ORGANS. 
 
 681 
 
 With the persistence of the generative glands is further associated 
 the necessity of enveloping the ova, which are liberated very early 
 (even before the development of the embryo), in a resistant shell 
 (p. 321). The free mobility which is exhibited by the 
 great majority of embryos of Bothriocephalus may also 
 be so far associated with the early liberation of the ova, 
 since it replaces the movement of the proglottides, 
 increasing the chances of the developing brood reach- 
 ing its destination. 
 
 The separated segments do not for long retain the 
 free and independent mobility which characterises the 
 proglottides, especially of the large-jointed Taeniadse. 
 This is evidently the necessary consequence of their 
 mode of separation which does not take place in 
 single segments, but in longer or shorter pieces, which 
 remain united. 1 
 
 The adult Bothriocephalidse live either in cold- 
 blooded or warm-blooded hosts, but only in carnivorous 
 forms, and almost always in those which feed on water 
 animals, and especially on fishes. Besides predacious 
 fish, these parasites especially infest water birds and 
 seals. I say especially, for there are also several land 
 animals, mostly mammals, which under certain circum- 
 stances harbour Bothriocephalidse. ArcJiigetes is a 
 unique and conspicuous exception, both in its occur- 
 rence and in its whole life-history, since it attains 
 sexual maturity, as has been already more than once Archlgetes Sie- 
 mentioned, in the intermediate host, and that a worm. *>oUi. ( x 60.) 
 
 The Distribution of the sexually mature worms suggests an 
 inference as to the occurrence of the young forms. The embryos 
 attain development especially in fishes, and more frequently in those 
 inhabiting rivers, than in marine forms. The other vertebrate groups 
 are not, however, wholly spared ; young Bothriocephalidse have been 
 found in frogs and reptiles, in birds and mammals (species of Spar- 
 ganum, Dies., and Ligula, Dies.), and even in animals which are 
 only temporarily associated with water. Even man is in this con- 
 nection, as we shall see, no exception. 
 
 1 According to the observations of Eschricht and others, there are, indeed, in fishes 
 some Bothriocephali, which regularly throw off all their joints during summer, so that only 
 the heads remain, again producing during winter new segments, all attaining sexual 
 maturity. In such cases the liberation of ova is not continuous, but periodic. To these 
 belong, apparently, those species especially which produce naked embryos, developing 
 within the joints, from thin shelled ova, with but little included nutritive material (p. 327) ; 
 species, therefore, which in their mode of reproduction present considerable resemblance 
 to the Taeniada}. 
 
682 DEFINITION OF BOTHKIOCEPHALUS. 
 
 The larvae are sometimes found, as in Sparganum, between the 
 muscles, usually, however, encapsuled in the liver and other viscera, 
 in localities, therefore, which we have already noted as the favourite 
 haunts of bladder-worms. In many cases at a certain stage they 
 leave their original resting-place, and pass into the body-cavity. This 
 is especially true of those species which attain a considerable size 
 within the intermediate host, particularly of Schistocephalus and 
 Ligula, as we have already noted (p. 676). The latter is, found in 
 the body-cavity of bleak, and sometimes a foot long and corre- 
 spondingly broad, so that in a few days it may attain its complete 
 development in the alimentary canal of a duck or goosander (Mergus). 
 The unsegmented Tricenophorus, with its two pairs of forked hooks, 
 is also not unfrequeutly found of a finger's length within the body- 
 cavity of the salmon or pike, within which, like the strap-worm 
 (Ligula), it breaks through its cyst when the latter becomes -too thin 
 to envelope the growing worm any longer. 
 
 There are altogether but few genera included in the family 
 Bothriocephalidae, as above defined. Of these only one claims special 
 attention here Bothriocephalus, which, apart from the doubtful B. 
 cristatus, Dav., includes two species parasitic in man (1.) B. latus, 
 the "Fascia" or "Taenia" of Plater and Andry (p. 410), whose true 
 nature was first recognised by Bremser in 1812 ; and (2.) B. cordatus, 
 first described by myself. To these must be added an unsegmented 
 species, which, in spite of its considerable size, is shown by its 
 structure and immaturity to be only a young form of a Bothriocephalus. 
 This worm was sent to me long since from Japan by Dr. Scheube, 
 and is identical with the Chinese form, since described by Cobbold as 
 Liyula Mansoni. 
 
 Bothriocephalus, Eudolphi (sensu stricto). 
 
 Dibothrium, Diesing. 
 
 The head is without hooks, and is distinctly marked off from the long 
 segmented body. Cirrhus and vagina usually open on the ventral surface 
 of the joints before the uterus ; rarely at the margin. The uterus, filled 
 uith ova, lies in the middle of tlie segments in the form of a coiled, often 
 rosette-shaped canal. In the larval fmm tlie body is unsegmented, but 
 more or less long, and ribbon-shaped. 
 
 The genus Bothriocephalus was first established by Eudolphi in his 
 famous "Entozoorum historia naturalis" (1809). In its original 
 connotation it included all jointed tape- worms, which are provided, 
 
DEFINITION OF BOTHEIOCEPHALUS LATUS. 683 
 
 not with the suckers (oscula suctoria) characteristic of the genus 
 Tcenia, but with suctorial grooves (bothria). This included forms of 
 very varied structure, with two or with four grooves, and with or 
 without hooks on the head. These were afterwards classified, and 
 that almost contemporaneously, by my uncle, Fr. S. Leuckart, in his 
 well-known monograph of the genus Bothriocephalus* and by Eudolphi 
 himself (1819) in his " Entozoorum synopsis." The genus was, indeed, 
 conserved in its whole extent, and indeed enlarged by my uncle to 
 the extent of including the segmented Tetrarhynchi, previously 
 separated by Eudolphi; but within the genus both Eudolphi and 
 Leuckart distinguished, according to the structure and armature of 
 the head, a number of smaller groups, which are still, for the most 
 part, retained, except that they now represent genera or even families. 
 The species which remain after the separation of the Tetrarhynchi are 
 those which, in Eudolphi's system, formed the "Inermes (gymno- 
 bothrii) dibothrii" of the first group, which Diesing afterwards 
 collected under the generic name Dibothrium. Including several 
 doubtful forms, the latter enumerated in this genus thirty-two species, 
 all of which, with the exception of one doubtful case, infest the 
 alimentary canal of mammals, birds, or fishes. The suctorial grooves 
 are said to be sometimes marginal, sometimes placed on the flat 
 surface ; but recent investigations seem to have made it questionable 
 whether any forms with marginal grooves really exist. The descrip- 
 tion, formerly so generally accepted, has, in the case of Bothriocephalus 
 lotus at least, proved to be erroneous. 
 
 Bothriocephalus latus, Bremser. 
 Taenia lata, Linnd, incl. T. vnlgaris, Linn6, et T. tenella, Pallas. 
 
 Bremser, " Lebende Wiirmer im lebenden Menschen," 1819, pp. 88-96. 
 Botticher, " Studien uber den Bau des Bothriocephalus latus," Archivf. pathol. Anak, 
 Bd. xxx., pp. 97-148. 
 
 Short-jointed, broad and flat, of considerable length up to 8 to 9 m., 
 "but usually shorter. The number of segments amounts, in long speci- 
 mens, to at least 3000 to 3500. With the exception of the last few, the 
 joints rarely measure more than 4 to 5 mm. (usually 3 to 3'5 mm.) in 
 length, while their breadth increases gradually to 10 or 12 mm. and 
 more (occasionally to as much as 20 mm). Posteriorly, the proportions 
 are somewhat altered, inasmuch as the breadth of the segments decreases 
 and the length increases, until the previous form is replaced by a square, 
 or even slightly elongated rectangular form. The body is usually thin 
 
 1 "Zoologische Bruchstucke," i. : Helmstedt, 1819. 
 
684 
 
 DEFINITION OF BOTHRIOCEPHALUS LATUS. 
 
 and flat, like a ribbon, especially towards the sides, while the median 
 portion, which contains the uterus, projects as a sort of pad. The 
 
 FIG. 858. Head of Bothriocephalu* latus. 
 ( x 8.) A, From the flat side ; B, From the 
 margin. 
 
 FIG. 357. BotJiriocephalut latu* 
 (nat. size). 
 
 anterior end of the "body is sometimes much contracted, and is then 
 relatively broad ; sometimes, however, elongated and thin, or even drawn 
 out into a thread-like neck, so that the liead, measuring 2 to 5 mm. in 
 length and 1 mm. in breadth, is marked off as an elongated swelling. 
 Viewed from the side, the head usually has, during quiescence, the form 
 of a mw*e or less elongated oval, with rounded, or occasionally with some- 
 what pointed, anterior end. A shallow furrow, which extends along tlw 
 margin of the latter, is continued posteriorly directly into the suctorial 
 groove, ivhich can be traced to the hinder end of the head in the form of 
 
DESCRIPTION OF BOTH RIO CEPHALUS LATUS. 685 
 
 a deep longitudinal cleft between the usually curved or wavy lips. The 
 pi*oportion of the body occupied by the barren joints varies according to 
 the form of the worm. When the anterior portion of the body is much 
 thickened, one finds the first ripe ova 500 to 600 mm. behind the head, 
 in segments which are about 5 mm. broad and 2 mm. long, and which 
 are preceded by at least 600 immature proglottides. The number of eggs 
 is at first small, but it increases so greatly that the substance of the body 
 is not unfrequently raised up into a sort of vesicle. Pari passu with this 
 increase, the modification of the uterus progresses. It lies at first coiled 
 up in the middle of the joint, extending from behind forwards; but 
 afterwards, when a larger number of ova are collected, and when the 
 uterus has in consequence increased in length beyond the limits of the 
 joint, it is disposed in a loop-like fashion right and left. In this way 
 there is formed in the middle of the mature joints that peculiar stellate 
 or rosette-shaped figure, which has been compared to a flower (Linne) or 
 heraldic lily (Pallas), and has been from of old regarded as the most 
 striking characteristic of the species. The loops lie in close proximity to 
 one another, projecting towards the sides like the leaves of a rosette 
 (" horns "). There are generally four or five of these on each side, and 
 more rarely six. They are approximated to various degrees, according 
 to the state of contraction of the segments, but are always so grouped 
 that the anterior include the generative apertures between them. These 
 latter are surrounded by numerous papillce. The cirrhus- pouch opens 
 along with the closely adjacent vulva into a common transverse slit. The 
 opening of the uterus lies a short distance behind. The yolk-sacs are 
 embedded in the cortical layer of the lateral 
 regions, both ventrally and dorsally, are seen as 
 dark points through the otherwise almost trans- 
 parent parenchyma, and give the sides of the body 
 a yellowish grey appearance. The greatest de- 
 velopment of the uterus, which corresponds with the . FIG. 359. Eggs of Both- 
 
 , -. 7.7 / .7 7 7 riocephalus latus : one of 
 
 greatest breadth of the worm, does not, however, them after the liberation of 
 coincide with the limits of the middle portion, but the yolk contents, (x 300.) 
 is found at a considerable distance further lack. Stretches of joints 
 of some length, and not individual proglottides, are separated off, and 
 the line of division always passes through the anterior half of a joint. 
 The muscular layers are, on the whole, but slightly developed, and 
 calcareous corpuscles have only a scattered distribution throughout 
 the body. The eggs have an oval form, and average in diameter O'Oo 
 mm. and 0'035 mm. They are enveloped in a simple brown shell, pro- 
 vided with a lid with a distinctly defined margin. 
 
 The larval form lives encapsuled in the pike, in the burbot (Lota 
 vulgaris), and probably in other river fishes. It rests let ween the muscles, 
 
686 DESCRIPTION OF BOTHRIOCEPHALUS LATUS. 
 
 or in various viscera. It is of inconspicuous size (5 to 10 mm.), and 
 has a flat club-like shape. The head is furnished with two superficially 
 situated suctorial grooves, and is usually retracted. 
 
 Although this worm differs strikingly from the Tccnice in the form 
 of the head, in the structure of the uterus, and in many other details 
 of organization, it was, till the seventeenth century, associated with 
 the large-jointed human tape-worms, and especially with T. saginata. 
 Its occurrence in the alimentary canal of man, and the general resem- 
 blance in form and size, counterbalanced a number of differences, 
 which were neither understood nor adequately appreciated. 
 
 As we have already mentioned (p. 410), Felix Plater in Basel was 
 the first to emphasise the differences between these 
 B two parasites, and to demonstrate the occurrence in 
 
 t;l\ A man of two distinct species of tape-worm, which 
 were for long distinguished as Tcenia prima and T. 
 secunda Plateri. Towards the end of the seven- 
 teenth century, the once renowned helminthologist 
 of Paris, Andry, bestowed on the T. prima of Plater 
 (i.e., on our Bothriocephalus) the title "Taenia a 
 e'pine" (T. vertebrata) on account of the external 
 protruding middle region, and almost vertebra-like 
 FIG. 360. Larvae disposition of the uteri. Fifty years later Bonnet 
 *iatua fromtke pike, emphasised the " stigmata umbilicialia " of this worm 
 C with retracted j n contrast to the " stigmata lateralia " of what we 
 
 head. (A n at. size, ., _ . - . ., , ,. .. m . , 
 
 B and C x 2). now call Tccmcc, and in the designation " Taema a 
 articulations courtes" directed attention to the physio- 
 gnomic difference, at once obvious in contrast to the large-jointed 
 tape-worms, " Tsenia a anneaux longs." 
 
 Important as these results were in the progress of our knowledge, 
 it is to be deplored that Bonnet, in consequence of a confusion, 
 equipped his worm with the head of a Toenia saginata* Although 
 the renowned naturalist of Geneva himself recognised his mistake 
 thirty -four years later, and corrected it by a description of the head of 
 a true Bothriocephalus (p. 413), he had unfortunately done much in 
 the meantime to establish the opinion that two kinds of short-jointed 
 tape-worms occurred as parasites in man, viz., the T. vulgaris, L. ( = T. 
 grisea vel membranacea, Pallas) and the T. lata, L., which latter was 
 supposed to unite the structure of a Bothriocephalus with a hook- 
 less Tsenioid head. Pallas thought he was even warranted in estab- 
 lishing, under the title T. tenella, a third species, with joints like those 
 of Bothriocephalus. 
 
 math, et phys. aoad. roy., Paris, t. L, p. 473, 1850. 
 
HISTORICAL ACCOUNT OF THE SPECIES. 687 
 
 It was only after Bremser had, in his beautiful researches, con- 
 firmed Bonnet's correction as to the structure of the head in the short- 
 jointed tape-worm, and had, for the first time, given a thorough and 
 faithful description and figure of the worm, that the errors of earlier 
 naturalists were explained. Since then it has been seen that the 
 worm under discussion is no Taenia, as Kudolphi still maintained, but 
 belongs to the genus Bothriocephalus, thus representing a group of 
 tape-worms otherwise not widely distributed among Mammalia. It 
 is only lately that we have become acquainted with forms infesting 
 the seal, polar bear, cat and dog, in regions where fish are plentiful, 
 which closely approach in structure and size the Bothriocephalus of 
 man, much more closely than the species occurring in fish, which are 
 mostly considerably smaller than B. latus. 
 
 But even Bremser allowed an erroneous description to persist, 
 which was only corrected about two decades ago by the researches of 
 Botticher already referred to. The mistake related to the position of 
 the head, the compression of which was, according to previous repre- 
 sentations, parallel to that of the body, while it is in reality in a plane 
 at right angles to the latter, so that the suckers belong to the flat- 
 tened sides and not to the margins, as was supposed. It is not diffi- 
 cult, on examining well preserved specimens, to corroborate Botticher's 
 result. 1 On the first head of a Bothriocephalus which I saw, and 
 before the appearance of Botticher's memoir, I remarked the error of 
 the old description, and corrected my former representation. 
 
 In the position of its suckers, this Bothriocephalus does not, there- 
 fore, differ from the other species of the genus. It is in correspon- 
 dence with its occurrence and habitat that the suckers of the worm, 
 which lies with its surface adjacent to the wall of the gut, should be 
 turned towards the villi on which they are fastened. 
 
 The Anatomy of Bothriocephalus latus. 
 
 Eschricht, " Anatomisch-physiologische Untersuchungen tiber die Bothriocephalen," 
 Nova acta Acad. Cces. Leop.-CaroL, t. xix., Suppl. ii., pp. 1-152, 1841. 
 
 Leuckart, " Parasiten," first edition, Bd. i., pp. 423 et seq., 1863. 
 
 Botticher, " Studien Uber den Ban des Bothriocephalus latus," Archiv /. patkol. 
 Anat. u. Physiol, Bd. xxiii., p. 108, 1866. 
 
 Stieda, ' ' Ein Beitrag zur Anatomic das Bothriocephalus latus," Archiv f. Anat. u. 
 Physiol., Jahrg. 1866, pp. 174-212 (Nachtrag, 1867, p. 61). 
 
 Sominer und Landois, " Ueber den Bau der geschlechtsreifen Glieder des Bothrioce- 
 
 1 Yet Kiichenmeister, in 1879, describes the suckers of this Bothriocephalus (Parasiten, 
 second edition, p. 243) as suctorial grooves flat, lateral, in the same direction with the 
 margins of the body (" Fovese marginales "). 
 
688 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 
 
 phalus latus," Zeitachr. f. wisa. Zool., Bd. xxii., pp. 40-99, 1872 ; also as first part of 
 '* Beitrage zur Anatomie der Plattwiinner," Leipzig, 1872. 
 
 Moniez, "Mdmoire sur lea Cestodes," pp. 125-183, Paris, 1881; also in Traveaux 
 dc Vlnst. de Lille, t. iii., fasc. 2. 
 
 When, in the year 1860, I was working at the structure of this 
 worm in preparing the first edition of this book, only the first of the 
 above-named memoirs had been published, and although it still forms 
 the basis of our knowledge of the anatomy of Bothriocephalus , it is 
 markedly defective, in the absence of any discussion of the relations of 
 this species to the other Cestodes. This defect tended to produce the 
 impression that the peculiarities of Bothriocephalus were much more 
 fundamental than is really the case. What Eschricht omitted, I 
 have attempted to supply. Since then we have learnt that this worm 
 is, in its general structure, at least in the general disposition of its 
 organs and in the nature of its tissues, closely allied to the Tcenice, 
 although strikingly different from them in other respects, especially 
 in the structure of its generative organs. In my description of the 
 latter I unfortunately fell into a misconception in regard to the yolk- 
 gland, which had been rightly interpreted by Eschricht and subse- 
 quently by v. Siebold, but which I mistakenly regarded as a deposit 
 of excreted matter. To Stieda is due the credit of discovering this 
 error, as also of elucidating our conception of the structure of the 
 genital apparatus by his discovery of the vaginal sheath, which had 
 been overlooked. What subsequent investigators have done has been 
 essentially little more than an extension and correction in matters of 
 detail. We shall find occasion to allude to these contributions in the 
 description which follows. 
 
 As we have already noted, Bothriocephalus agrees in its general 
 structure with the Tcenice. In both can be seen (best in thin trans- 
 verse sections) the same cuticle, with the subjacent, crossed fibrous 
 layers, the same cortical and central layers, and the same disposition of 
 the generative organs. The latter lie, as in Tcenice, for the most part 
 within the central layer, the male generative glands and the vas 
 deferens turned to the dorsal surface, the uterus and ovary towards 
 the ventral, where the generative openings are also situated. The 
 only thing which seems unusual in Bothriocephalus is the presence 
 of numerous large heaps of granules, lying in a layer between the 
 subcuticular layer and the longitudinal cortical muscles, which they 
 push out to a considerable extent, especially in the lateral regions of 
 the segments. These are the structures which I formerly erroneously 
 regarded as deposits of excreted substance, although they had been 
 already shown by Eschricht to be connected with the female organs, 
 and had been described as organs which, though not ovaries, played a 
 
THE MUSCULATURE AND CONNECTIVE TISSUE. G89 
 
 rdle in the equipment of the eggs, and were, in other words, as v. 
 Siebold first precisely defined them, yolk-glands. 
 
 FIG. 361. Transverse sections through the body of Bothriocephalus lotus. 
 A , At the level of the cirrhus-pouch ; J5, In the posterior half, through the 
 female generative organs. The testes, uterine horns, yolk-sacs, and nerve 
 cords are also seen. ( x 10.) 
 
 The Muscle Layers, like the reproductive organs, are disposed as in 
 the Tcenice. It is not of much importance that the longitudinal 
 fibres of the cortex are more thickly packed towards the yolk-glands, 
 and therefore towards the outside, than in the neighbourhood of the 
 central layer, which in the Tcenice, on the contrary, exhibits the 
 greater number of fibres. Nor is it very remarkable that the muscu- 
 lature of this Bothriocephalus is inferior in strength and degree of de- 
 velopment to that of the large-jointed tape-worms, and especially to 
 that of T. saginata. There is further a difference between the two 
 forms, in that the sagittal fibres of Bothriocephalus, instead of being 
 uniformly distributed, are in the middle layer for the most part 
 grouped in strands, forming a sort of framework in which the 
 testicular vesicles and the uterine coils are embedded. In the 
 younger joints this disposition is not yet perceptible ; it only arises in 
 consequence of the increase in the size of the generative organs, by 
 which the adjacent fibres are pressed to the side. 
 
 The Connective Tissue consists of cells of unusual size, and more 
 sharply defined than in the case of most Cestodes. This is in 
 part due to the nature of the protoplasm, which is marked off as an 
 almost gelatinous clear mass from the duller intermediate substance, 
 and in part also to the development of a fibrillar network, which 
 envelops the cells in its meshes. The vesicular tissue in the median 
 region is most distinct and beautiful, especially in the neighbour- 
 hood of the cirrhus-pouch, where the cells not unfrequently grow 
 to the size of O026 mm. and more. The fibrous network is here most 
 strongly developed, and may be frequently observed to be of distinctly 
 muscular character, since the fibrils are seen to come into connection 
 with the processes and terminal branches of the true muscle -fibres. 
 
 , 2 X 
 
690 THE ANATOMY OF BOTIIRIOCEPHALUS LATUS. 
 
 Towards the sides the cells become smaller and less distinctly 
 limited, sometimes so slightly that the ground substance presents in 
 some parts the same appearance as in the Tcenice. The layer of 
 subcuticular spindle-cells is especially well-defined from the vesi- 
 cular tissue. 
 
 The Calcareous Corpuscles (Kernkornchen, Eschr.) of Bothrioccphalus, 
 as we have already noted, occur separately, and on the whole but 
 sparsely. 1 They are at once most abundant and largest (up to 0*015 
 mm.) in the immature joints. They are especially met with between 
 the longitudinal fibres of the cortex, but they are not wholly absent 
 in the central layer. It appears, indeed, as if the individual speci- 
 mens exhibited great variations in the number of calcareous corpuscles 
 present. In the ripe old joints they seem not unfrequently altogether 
 absent. 
 
 The Longitudinal Vessels and nerves, which have been already (p. 
 679) described within the head, may be traced in transverse sections 
 nearly to the sexually mature joints. They differ only in so far as 
 they increase with the growth of the body, though not in the same 
 proportion. With this increase in thickness a larger space is left 
 between them. They are not to be looked for, as in the Tcenice, 
 in the outer angles of the middle layer, but, as Eschricht ob- 
 served, further inwards, near the middle of the two lateral regions 
 (Fig. 361). 
 
 In the ripe segments the relations are changed, since the vessels, 
 which elsewhere hardly ever measure more than 0*07 mm., and are 
 also considerably less in widtli than the longitudinal vessels of the 
 Tcenice, gradually become narrower till at last they are no longer 
 recognisable. They share the fate of the vessels which extend 
 beneath the subcuticula, traces of which I was able to follow on my 
 sections only as far as the neck. It cannot, however, be concluded that 
 the vessels cease here, but only that in hardened specimens they are 
 no longer to be detected, owing to their thinness, and the insufficient 
 resistance of their walls. For the elucidation of the course of the 
 vessels in Bothrioccphalus, fresh specimens are necessary, and these 
 are not always procurable. This being so, it is readily intelligible 
 that the whole structure and disposition of the vascular system in 
 this worm have not yet been elucidated. "VVe do not know whether 
 the longitudinal vessels, in their course backwards, remain undivided, 
 
 1 Lamlois and Sommer, and Moniez are mistaken in asserting that, in the first edition 
 of this work, I wholly denied the presence of calcareous corpuscles in Bothiioccphalus. 
 I have always spoken only of a relative absence, and on page 425 have, in noting 
 their size, expressly stated that they agree in appearance and nature with those of the 
 larger Tcenice. 
 
THE NERVOUS AND REPRODUCTIVE SYSTEMS. 691 
 
 or, if connected, how this takes place. Only so much has been found out, 
 that, besides the longitudinal vessels extending internally, a fine super- 
 ficial vascular network is present here, as in other species. This has 
 not only been established by the facts which we have already com- 
 municated, but has also been corroborated definitely and in detail by 
 the results of Knoch 1 and Botticher, 2 who have observed in the head 
 of Bothriocephalus a close network of fine vessels, which becomes 
 posteriorly coarser and more widely meshed, and finally (according to 
 Botticher) passes on each side into several wider longitudinal vessels, 
 which are mutually connected by an irregular anastomosis. Moniez 
 estimates the number of these superficial longitudinal vessels at about 
 twenty. As to the connection with the more deeply situated longi- 
 tudinal vessels, nothing is known, nor has any ciliation been yet 
 observed in JBothriocephalus latus. 3 
 
 The Nerve Cords, which can be traced along the whole length of 
 the body, and which with increasing size of the joint become 
 gradually thicker (from O25 mm. up to O'l mm.), change their 
 position after the disappearance of the deeply seated longitudinal 
 vessels, inasmuch as they are pressed not only farther inward in 
 consequence of the stronger growth of the lateral borders, but also 
 towards the ventral transverse muscles by the testicular sacs on the 
 dorsal surface. They exhibit the same apparently spongy structure 
 as the nerve tracts of the Tcenice, and, like the latter, have been 
 designated by Sommer "plasmatic" longitudinal vessels. Other 
 observers have compared them to the longitudinal canals of the 
 Tcenice, except Eschricht, who thought he had discovered in them the 
 limbs of a bifurcated divided alimentary canal. Cerebral ganglia, 
 if present at all as distinct structures, are at any rate very small 
 and insignificant, as the absence of specialised suckers would indeed 
 lead us to suppose. It seems probable that the two lateral cords 
 are united at the anterior end of the head by a simple transverse 
 connective. 
 
 The peculiarities of Bothriocephalus, as above noted, may scarcely 
 appear very- striking or characteristic ; but it is very different when 
 we turn our attention to the next group of organs. 
 
 The Reproductive Organs. In the nature and disposition of the 
 genital apertures, in the structure of the uterus, in the arrangement 
 
 1 " Naturgeschichte d. breiten Bandwurmes," 1862, p. 118. 
 
 2 Archivf. pathol. Anat. u. PkysioL, Bd. xlvii., p. 370, 1869. 
 
 8 The statement of Moniez (loc. cit., p. 143) that the vascular network of the head 
 opens externally on the lips of the suckers by a large number of small oscula, requires 
 corroboration. The "ampoules pyriformes," as the oscula are designated, recall the 
 " doubtful bodies," perhaps unicellular glands, previously described (p. 678). 
 
692 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 
 
 and development of the yolk-glands, peculiarities are to be observed 
 which never occur in the Tcenice, and which prove this tape-worm to 
 belong to a markedly divergent group of Cestodes. The same charac- 
 teristic distinctions obtain, with more or less uniformity, in the 
 related species of Bothriocephalus, and especially in the larger forms 
 which are found in mammals. 1 
 
 We have already outlined the steps in the historic growth of our 
 knowledge of these peculiarities, nor shall we do more than recall 
 that it was not the nearly related parasites which supplied the basis 
 for the distinction and definition of the species under discussion, but 
 the large-jointed Tcenice of man. 
 
 The Genital Apertures and their surroundings will first occupy us 
 in describing the reproductive system in detail 
 
 A first glance at a ripe adult joint seems only to reveal two 
 genital apertures. Situated one behind the other, separated by a 
 short distance (0'3-0*4 mm.), varying slightly with the state of 
 contraction, these apertures lie in the middle region of the ventral 
 surface, somewhat approximated to the anterior margin of the joints. 
 They are usually found, as Eschricht reports, on the posterior limit 
 of the first quarter of the joint, yet cases may be observed where 
 they have been displaced by the state of contraction, either further 
 forwards or backwards. Even Linnd observed these two openings, 
 but thought erroneously that they occurred only in certain specimens 
 (his Tcenia vulgaris), and that in others (T. lata) only a single 
 aperture was present. 
 
 The anterior opening is seen on closer examination to be the male. 
 It is larger than the one behind, and forms usually a gaping trans- 
 verse cleft, from 0'25 to 0*34 mm. broad, the upper lip of which is 
 protruded outwards by the cirrhus-pouch which lies above it. The 
 penis is sometimes seen projecting as a small filamentous appendage. 
 The second, also transverse, aperture, which serves for the exit of the 
 ova, is scarcely half as broad as the upper, but is also somewhat 
 raised, so that the whole area surrounding the genital apertures 
 almost always protrudes in the form of a slight elevation. In fresh 
 specimens this protruding area is readily recognisable through its 
 whitish colour, which is due, not wholly and exclusively to the 
 subjacent tissue, but also to numerous small papillse, which occupy 
 
 1 See on these forms Krabbe, " Recherches helminthologiques en Danemark et en 
 Islande," Copenhagen, 1866, pp. 27-39. The various species are somewhat difficult to 
 distinguish, but I think T am warranted, on the strength of repeated investigations, in 
 affirming that in the organization of the reproductive system, and especially in the 
 structure of the uterus, in the character of the papillary area, and in the disposition of 
 the yolk-glands, differences obtain among them not less than those which distinguish the 
 large -jointed Tcemce. 
 
THE GENITAL OPENINGS. 
 
 693 
 
 the area, and are specially closely grouped between the openings. 
 On microscopic examination they are seen to be conical elevations 
 
 w 
 
 
 c. 
 
 FIG. 362. Mature joint of Bothriocephalus lotus, g., genital apertures ; p., 
 papillary organs ; y.g., yolk-glands; y.d., " yellow ducts "j c., cirrhus protruded 
 (after Eschricht). (x 8.) 
 
 of the cuticle (O02 mm. high, 0'03-0'04 mm. broad), which enclose 
 in their basal portion a single or double (rarely triple) clear, nuclear, 
 or knob-like body. Although Eschricht, who described these 
 structures quite correctly, and indeed better than his successors (till 
 Stieda), x believed they were cutaneous glands, we shall probably not 
 be far astray in regarding them as tactile papillae. 
 
 If the anterior genital opening be more closely examined, and that 
 preferably and most satisfactorily in longitudinal sections through 
 the papillary region, it does not require long to be convinced that 
 the former does not by any means solely belong to the male 
 apparatus. At the base of the opening one can see, close behind the 
 aperture of the cirrhus-pouch, a second smaller opening, which was 
 discovered even by Eschricht, although he was unable to determine 
 its true nature. He suggests the possibility that it leads into the 
 anterior loops of the uterus, yet he had not any doubt that the opening 
 further back was to be regarded as the os uteri. 
 
 Through the observations of Stieda, we have attained to a clear 
 conception of the nature of this second aperture, adjacent to that of 
 the cirrhus. We know now that it (Fig. 363) is the aperture of the 
 vagina, of a duct which was already seen by Eschricht, and sub- 
 sequently by Botticher, who denned it as the vagina, though both 
 made the mistake of maintaining its connection with the opening of 
 the uterus. 
 
 1 Braun has overlooked former descriptions of this papillary area, and regarded him- 
 self as its discoverer, loc. cit. , p. 42. 
 
694 . THE ANATOMY OF BOTHEIOCEPHALUS LATUS. 
 
 We have already seen the importance of this discovery of the vagina 
 and its aperture for the right understanding both of the morphology 
 and physiology of the reproductive organs of Bothriocephalus. 
 
 Since the vaginal aperture, as above noted, 
 lies at the bottom of the anterior genital 
 opening, which also includes the opening of 
 c the cirrhus-pouch, and was till Stieda's dis- 
 covery described as simply the male aperture, 
 there is a certain justification for speaking of 
 a sexual cloaca in Bothriocephalus. It must, 
 however, be kept in mind that this cloaca is 
 in nowise to be associated with the structure 
 of the same name in the Tcenice. While the 
 latter, in virtue of its depth and narrow 
 aperture, appears as a morphologically inde- 
 pendent structure, which does not alter its 
 form or character even when the penis is 
 protruded, the cloaca-like cavity in the form 
 under discussion is different, inasmuch as, on 
 protrusion of the penis, it is more or less com- 
 pletely smoothed out by the retraction of the 
 lips ; and that so far that the vaginal aperture 
 comes to lie exposed on the surface of the 
 joint, below that of the cirrhus, in a situa- 
 tion which in other species is the persistent 
 one, e.g., in B. maculatus of the leopard and 
 lion, where there is almost no genital cloaca. 
 This being so, it is perhaps more correct to 
 regard the genital pore of this worm as the 
 result of simple invagination, as Eschricht 
 had indeed done in designating the lip-like 
 marginal swelling the " prseputium." 
 
 The Cirrhus, when protruded, is seen as a slender cone (Fig. 362), 
 not unfrequently protruding half a millimetre, or even more, out of 
 the genital aperture. It has accordingly a much more considerable 
 size than in the cystic tape-worms, in which (T. saginata) it is hardly 
 ever larger than 0'18 mm. At its base it measures in the present 
 species fully 01 mm., which is more than double its measurement at the 
 end. The canal which penetrates it, and opens at its apex, collapses 
 in the empty state, but is not unfrequently filled with spermatozoa, 
 and then occasionally measures as much as 0*02 mm. or more. 
 
 In spite of its considerable size, the cirrhus of Bothriocephalus is 
 nothing more than the externally evaginated anterior portion of the 
 
 FIG. 363. Longitudinal 
 diagrammatic representation 
 of the three generative ducts 
 in their connection with the 
 the genital apertures and 
 with one another, v.d., vas 
 deferens; c.p., cirrhus-pouch; 
 r., vagina ; u., uterus. 
 
THE CIRRHUS-POUCH. 695 
 
 cirrhus-pouch. As such it consists mainly of connective tissue, and 
 that of the very vesicular kind which we have already found in the 
 matrix of the worm. 
 
 The Cirrfius-PoucJi can only be adequately studied by the method 
 of sections. From superficial preparations merely, only an imperfect 
 survey of the arrangement can be obtained. In such the cirrhus- 
 pouch simply appears as a roundish disc of considerable size (Q'4-0'44 
 mm.), which lies superiorly behind the porus genitalis, and extends 
 to the anterior margin of the joint. This disc is seen on close exami- 
 nation to be the optical section of a hollow muscle, which has when 
 quiescent a somewhat regular oval form, and is inserted on the ventral 
 surface of the joint, i.e., on the porus genitalis, usually with an anterior 
 angle of from 75 to 80. The posterior pole of the pouch usually 
 lies higher than the porus genitalis, but is, in consequence of the 
 considerable length of the pouch (O5-0 - 55 mm. in the ripe joints), 
 so nearly approximated to the dorsal wall, that it is only separated 
 by a small interval (O'Ol mm.) from the dorsal transverse muscle- 
 bands. The opposite ventral pole is different, since it penetrates 
 the transverse muscle-sheath and the whole cortical layer as far as 
 the subcuticula ; and the latter has also but a slight thickness where 
 it lies above the pouch. 
 
 FIG. 364. Transverse section through the body of Boihriocephalus 
 latus at the level of the cirrhus-pouch. ( x 10.) 
 
 The canal which penetrates the cirrhus-pouch is a direct continua- 
 tion of the seminal duct, and is morphologically nothing but its 
 terminal portion. Its peculiarities are secondary adaptations to 
 copulatory functions. Apart from the musculature which surrounds 
 it like a bulb, its peculiarities consist especially in this, that instead of 
 pursuing a straight course, it is rolled up in close spiral coils. This 
 is especially true of that portion of the duct which penetrates the 
 (dorsal) half of the bulb, and which, being always filled with semen, 
 serves as a sort of seminal vesicle. The portion further forward is 
 simpler ; the spiral coils are disposed in a less extensive zigzag (Fig. 
 361). Only the outermost portion opening freely at the end of the 
 cirrhus-pouch exhibits an almost straight course. It is this anterior, 
 partly stretched, partly zigzag, twisted portion of the seminal duct 
 which is evaginated by the muscular pressure of the cirrhus-pouch to 
 form the cirrhus. It differs histologically from the posterior portion 
 
696 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 
 
 only in so far as it is internally clad by a somewhat firm, doubly 
 contoured cuticle, which is continued at the outer openings directly 
 into the cuticle of the cloaca, and like it rests on a distinct subcuti- 
 cular layer of cells. This can hardly, of course, be compared with the 
 subcuticular layer covering the body. It has but an insignificant 
 thickness, and gradually vanishes posteriorly towards the seminal 
 vesicle. Like the latter, this zigzag coiled posterior portion of the 
 canal is usually filled with semen, and much widened, while the 
 extended terminal portion remains always empty and closed. 
 
 The cirrhus-pouch, which surrounds the above-described canal like 
 a bulb, protrudes the anterior portion of the cirrhus, and thus brings 
 about copulation. The muscles admit of simpler and sharper analysis 
 than in Tcenice, and are evidently disposed for the discharge of this 
 function. 
 
 The external wall (Eschricht's "capsule") is formed of a thick 
 sheath of muscles, whose fibres, as Landois and Sommer rightly 
 observed, generally run in the longitudinal direction of the bulb, 
 extending from the rounded dorsal pole to the genital pore. Near 
 the latter they bend for the most part from their former direction, 
 mingling with the adjacent longitudinal fibrous bands, and ramifying 
 in the cortical layer. By the contraction of these fibres the cirrhus- 
 pouch is pressed diagonally downwards against the yielding floor of 
 the cloaca, so that the latter is arched outwards, and the inferior seg- 
 ment of -the bulb protruded like a plug. The canal is not, however, 
 evaginated without the pressure of the circular fibres, which lie partly 
 isolated among the longitudinal and partly united in plexiform fashion, 
 penetrating (iri the anterior half of the cirrhus-pouch as far as the 
 evagination occurs) even into the deeper connective-tissue masses, and 
 being thus eminently capable of affecting these. Under the pressure 
 of the circular fibres the inferior pole of the pouch assumes first of all 
 a mammiform shape, until, through the evagination of the enclosed 
 canal, whose lips represent the pars minoris resistentice, the cirrhus 
 proper is subsequently protruded. It need not be specially men- 
 tioned how during this operation the coils of the canal are unwound 
 and the spiral turns of the posterior portion straightened. 
 
 Not only the protrusion of the cirrhus, however, but also its retrac- 
 tion, is fitly secured by radial fibres, which spring on every side from 
 the muscular envelope of the cirrhus-pouch, penetrating the cortical 
 substance at varying intervals, finally uniting with the external wall 
 of the pouch, that is, with its subcuticular layer. The cirrhus-pouch 
 has its own special retractor muscles, in the form of sagittal fibres, 
 which pass from the dorsal surface of the joint, and are inserted on 
 the adjacent segment of the muscular capsule. 
 
THE VAS DEFERENS. 697 
 
 The thick layer of annular fibrils, which surrounds the coils of the 
 seminal duct, effects probably only the forward movement of the 
 internal seminal mass, forcing it into the cirrhus. 
 
 That the cirrhus is really a copulatory organ is, in spite of Lan- 
 dois and Sommer's contradiction, all the more certain since the sensory 
 papilla? on the genital area point clearly to a sexual association of the 
 joints ; but this is still far from having been verified by observation. 
 
 The Vas Defer ens is directly continuous with the canal within the 
 cirrhus-pouch, as has been described above, and the cirrhus-pouch 
 itself is a muscular apparatus developed round about it. One might 
 therefore readily suppose that the entrance of the vas deferens into 
 the pouch coincided with its distal pole, as its aperture does with the 
 proximal. Such is not, however, the case. The entrance of the vas 
 deferens occurs rather at the portion turned backwards, towards the 
 hinder border of the joint, and at a considerable distance from the end 
 of the cirrhus-pouch, so that the latter arches above it in the form of 
 a hemispherical protuberance, while the spirally coiled canal within 
 forms in its windings an arch open posteriorly. It is of course only 
 the quiescent state of the cirrhus-pouch which exhibits this appear- 
 ance, for with the protrusion of the cirrhus the caeca! ly projecting 
 portion of the pouch undergoes a reduction, in consequence of which 
 the insertion of the vas deferens becomes apparently altered. 
 
 Just at its point of entrance into the cirrhus-pouch the vas 
 deferens is further surrounded by an ovoid bulb, which, though of 
 course much inferior in size, rarely measuring mor6 than 0*2 mm. 
 long by 0*4 mm. thick, undeniably recalls the structure of the cirrhus- 
 pouch by its muscular character, and by the coiled course of. the canal 
 within it. There are indeed many differences in detail. Not only is 
 the connective tissue much less developed in proportion to the mus- 
 cular tissue, but the latter seems to be somewhat differently disposed, 
 since the radial muscles are absent, and the others are united in a 
 close web, whose fibres extend for the most part annularly, partly, 
 however, crossing one another diagonally. Longitudinal fibres are 
 only present in small numbers. 1 It can hardly be doubted that this 
 muscular bulb serves to force into the cirrhus-pouch the semen which 
 frequently collects in considerable quantity within the canal. 2 Ac- 
 cording to Botticher, it simply represents a seminal vesicle. 
 
 The vas deferens is seen as a highly coiled canal, extending on 
 
 1 I could not seethe strong cilia which Moniez (loc. cit., p. 144) found within the 
 bulb, and which had a distinctly cellular character ("les cils sont volumineux, leur 
 nature cellulaire ne peut (Hre mise en doute "). Nor could I perceive the cilia in the 
 vagina which he has described (ibid., p. 148). 
 
 2 Eschricht overlooked this apparatus, for the citation by Stieda and others to the 
 
698 
 
 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 
 
 the dorsal surface of the uterus, the loops of which it accompanies 
 in more or less close apposition (Fig. 365), but on the whole the 
 bendings which it exhibits are smaller and less ample. There is an 
 obvious difference here between the present species and the Tcenice, 
 and this is further emphasised by the fact that the vas deferens in 
 
 this worm is not only considerably 
 wider, but also bears a sheath of 
 circular muscle fibrils, which, like 
 the bulbar swelling at the upper 
 end, serve to force forward the en- 
 closed spermatozoa. According as 
 the number of the latter is large or 
 small, the width of the canal varies, 
 &c increasing sometimes from 0'035 
 mm. to double that and more, be- 
 ov sides exhibiting, at certain places, 
 considerable varicose swellings. 
 This is seen most strikingly and 
 . most frequently at the lower end, 
 
 FIG. 365. Male generative organs of . * * 
 
 Eothrioccphalus latus, seen from the dor- which, being tilled With Semen, not 
 
 sal surface ; c.j)., cirrhus-pouch i ; *., swell- un f requ ently forms a Conspicuous 
 ing adjacent to it; v.d., vas deferens ; .c., ? \ 
 
 seminal cistern; <., testes; <., uterus; "Seminal Cistern (LandoiS and 
 
 .g. t shell-gland ; ov., ovary, (x 20.) Sommer), shining through the first 
 coils of the uterus, just in front of the ovary, in the form 
 of a darkish, saccular, irregular body, sometimes measuring 0'2 
 mm. in thickness. The sperm mass is brought into this re- 
 ceptacle by the afferent canals, which in a variable, but always 
 limited, number lead into the "cistern" from right and left, and 
 connect it through their much ramified lateral branches with 
 the testicular vesicles. The irregularity in the number of afferent 
 ducts is due for the most part to a very early bifurcation. I have 
 seen joints in which the lower end of the vas deferens divided into 
 two limbs, which extended almost at right angles into the lateral 
 areas, there to ramify further, and also others in which, on either 
 side, three or four collecting ducts led into the " cistern." The branches 
 of the collecting ducts, or the ducts themselves when several occur, 
 are directed both backwards and forwards. Nor are they by any 
 means confined to the area of the joint to which they really belong, 
 but extend beyond the boundaries, coming into connection with the 
 superior testicular vesicles of the following joint. 
 
 contrary refers to a second small vesicle within the cirrhus-pouch (loc. cit., p. 50), and can- 
 not apply to the appended bulb. The latter was first discovered, described, and explained 
 by myself. 
 
THE STRUCTURE OF THE TESTES. 699 
 
 The more the ramification progresses, the thinner and more deli- 
 cate do the twigs become, until they finally escape detection. Only 
 in isolated cases can they be seen uniting with the testes (which then 
 appear stalked), and especially with those which lie nearest the median 
 area. They have, as a rule, a comparatively straight course, and 
 frequently seem, especially near the seminal cistern, to result from a 
 dichotomous branching. 
 
 The Testes themselves exhibit exactly the same structure and dis- 
 position as in the large-jointed Tcenice. The vesicles have a similar 
 irregularly oval or spherical form, and have when full-grown an 
 average diameter of 0'1-0'13 mm. They extend in a thick layer over 
 the lateral portions of the middle layer (Fig. 361), and are here and 
 there insinuated between the loops of the uterus. Towards the lateral 
 borders they are more closely grouped, and the transverse diameter 
 becomes diminished in consequence. Stieda has estimated their 
 number at about 320-400 in each joint, while Landois and Sommer 
 compute it at 1000-1200. According to my estimate, the former 
 is below, the latter above the mark. In each lateral area I count 
 twenty-three in a transverse line, and sixteen in a longitudinal, and 
 thus compute a total of between 600 and 700, which agrees well with 
 Eschricht's estimate of 700. 
 
 Both Landois and Sommer and Moniez describe the testes as simple 
 lacunae in the tissue of the middle layer, but with reagents I can dis- 
 tinguish the coagulated contents from a distinct, delicate, enveloping, 
 cuticular membrane. The striated substance within the mature 
 vesicles consists of extremely fine long spermatozoa, which are grouped 
 in numerous bundles, or rolled up, and which (according to Stieda 
 and Sommer and Landois) bear at one end a strongly refringent head. 
 Between these can be seen separate aggregates of small (0*005 mm.) 
 nuclear cells (Kernzellen 1 ), which occur in much greater abundance in 
 the unripe vesicles, where they may, indeed, form the whole contents. 
 Tt is hardly necessary to remark that these cells in course of time 
 develop into spermatozoa. Their occurrence in the ripe testes also 
 shows that the formation of spermatic elements in Uothriocephalus 
 is not, any more than that of the ova, restricted to a definite period, 
 as in the Tcenice, but continues as long as the vegetative life of 
 the joints. 2 
 
 The dark balls which not unfrequently occur in the ripe joints 
 between the coils of the uterus and of the vas deferens, are, in spite of 
 
 1 Deceived by these cells, Botticher (loc. cit., p. 121) thought that each sperm-filled 
 testis was a coil of fine canals, with an internal cellular lining. 
 
 2 According to Moniez, the spermatozoa are formed freely in the tissue of the tape- 
 worm, roll themselves up in spherical masses, and make their way independently to the 
 ramifications of the vas deferens (loc. cit., p. 147). 
 
700 
 
 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 
 
 their considerable size (up to 0'25 mm.), to be regarded as degenerated 
 testicular vesicles. This supposition is at least more probable that the 
 interpretation of Landois and Sommer, according to which they are 
 " portions of the vas deferens or of the large seminal ducts " which 
 have been constricted off, and whose contents have undergone fatty 
 metamorphosis. 
 
 The Female Reproductive fogans. The Vagina, as above noted 
 (Fig. 363), opens just below the cirrhus-pouch into the bottom of the 
 genital cloaca. In spite of the approximation of their apertures, 
 their mutual position is such that the possibility of self -fertilisation 
 
 
 ; ut. 
 
 seems all but excluded. For such 
 a purpose the cirrhus would have 
 to bend at an acute angle backwards 
 and downwards, for which it is the 
 less capable, since the cloaca is 
 flattened out when extruded, and 
 external pressure cannot therefore 
 act upon it, as in the Tcenice (p. 309). 
 The vulva is a somewhat wide 
 (0-06 to 0-085 mm.) and funnel- 
 shaped, but yet short, invagination 
 of the external envelope of the 
 body, which is directly continued 
 into the much narrowed vaginal 
 
 The 
 
 latter extends, as can be seen in 
 longitudinal sections, for some dis- 
 tance below the cirrhus-pouch to- 
 wards the dorsal surface (Fig. 367). It bends, however, before it 
 reaches the opening of the vas deferens, at an acute angle towards the 
 ventral aspect, and finally extends almost straight backwards, in the 
 middle line, upon the transverse muscle layer of the joint. Beaching 
 the anterior border of the ovary, it leaves the ventral muscle-layer, 
 passing on to its dorsal surface, on which it continues its course for 
 some distance further. The posterior end of the vagina usually forms 
 a more or less large (012 to 0'2 mm.) saccular dilatation, filled with 
 semen. This is to be regarded as a receptaculum seminis, although it 
 is not in any way histologically different from the rest of the canal, 
 and is further so slightly separated anatomically, that when quite 
 filled it is for some distance quite continuous with the adjacent 
 portion of the canal. This caecal vaginal receptacle communicates by 
 a narrow duct, as we shall -presently see, with the hinder end of 
 the uterus and with the other portions of the female apparatus. 
 
 FIG. 366. Female generative organs of , /n no , N 
 
 Sothriocephalus latui, from the ventral Canal (0'024 to 0'04 mm.), 
 surface, or., ovary; r.a., receptaculum 
 seininis ; t.g., shell-gland ; ut., uterus ; 
 ut.o., uterine opening; v., vagina; v.o. t 
 vaginal opening. ( x 20. ) 
 
THE VAGINA AND (JTERUS AND THEIR OPENINGS. 
 
 701 
 
 The most important histological character of the vagina is the 
 presence of a muscular layer consisting, for the most part, of circular 
 fibres, which begins at the base of the vaginal 
 entrance, and acquires a specially strong de- 
 velopment in the dilated sac. The internal 
 lining of the canal is formed of a thin, but 
 sharply defined cuticle, which is continued at 
 the vaginal opening into the cuticular cover- 
 ing of the body. 
 
 It was only after the discovery of this 
 vagina that it became possible to homologise 
 the structural relations of the reproductive 
 organs in Bothriocephalus with those of the 
 Tcenice. "We know now that in the former as 
 well as in the latter the uterus serves only 
 for the reception of the ova, and the differ- 
 ence between it and the Tcenice is thus 
 essentially reduced to this, that the uterus is 
 not closed, but has an opening through which 
 the ova pass outwards. 
 
 The Uterine Aperture, as has been already 
 described, is seen a short distance (Fig. 367) 
 behind the genital cloaca, at an interval of 
 between 0'25 and 04 mm., according to the 
 state of contraction of the segment. It is sur- FIG. 367. Diagrammatic 
 
 ... . i-i i , Viii representation of the course 
 
 rounded by margins Which are but little and connections of the vagina, 
 
 Swollen, has a width of 015 mm., and, a . 8 seen in longitudinal sec- 
 
 , , . , i f n r. A tion. v.d., vas deferens ; 
 
 rapidly narrowing, leads into a canal (of (r04 C-J)M dn-hus - pouch 
 mm. in diameter) which is inserted at right 
 angles to the ventral surface, penetrates 
 the cortical layer, and then somewhat sud- 
 denly widens into the upwardly directed first coil of the uterus 
 which lies right or left of the cirrhus-pouch. 
 
 The Uterus, whose true structure was first recognised by Eschricht, 
 consists of a simple coiled canal, which extends from behind forwards 
 in the internal layer of the joints, and at the height of its develop- 
 ment occupies the greater part of the whole median portion. The 
 windings extend alternately right and left across the middle line, and 
 the adjacent bands of their loops at first suggest the lateral processes, 
 whjch we have already seen in the large jointed Tcenice. On closer 
 examination, however, this resemblance is seen to be an illusion, 1 and 
 
 vagina; ., uterus; ut.o., 
 uterine opening ; f.c., fertil- 
 ising canal ; o.d, oviduct ; 
 s.g., shell-gland. 
 
 1 Botticher's statement that a direct connection exists in the middle line between the 
 loops which here cross each other is based on a misinterpretation. 
 
702 
 
 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 
 
 that most distinctly in undeveloped or only half-developed joints, in 
 which the course of the uterus can often be followed throughout its 
 whole extent. It is only when the ever - increasing mass of ova 
 gradually distends the canal, when the limbs of the loops become not 
 only longer but broader, partly overlapping one another, that the 
 uterus assumes the form of a " rosette," or of a " heraldic lily," which 
 was regarded by the older helminthologists as the most important 
 distinctive character of the species. 
 
 The number of loops, or of " horns " as they are usually, but in- 
 aptly, designated, is in JBothriocephalus usually five (four to seven) on 
 either side. When fully developed they possess a width of about 
 0*5 to 1 mm., and a length of about 2 to 2'5 mm., so that the total 
 length of the uterus is usually between 25 to 30 mm. The anterior 
 
 FIG. 368. Ripe joint of BothrioccpJialus latus with the uterine rosette. ( x 6.) 
 
 horns, though not always the longest, are pretty generally the 
 thickest, and in the older joints are usually distinguished from the 
 others by a dark colouring. They are situated at the sides of the 
 uterine opening and of the cirrhus-pouch, on either side of which they 
 diverge upwards, while the middle horns usually exhibit a more trans- 
 verse course, and the posterior generally diverge backwards. So it is 
 at least when the joints are somewhat strongly contracted. With the 
 increase in length, the various loops shorten and separate somewhat 
 from one another. In assuming a more parallel disposition, the above 
 noted resemblance to the joint of a Tcenia becomes more marked and 
 deceptive, but the absence of a marginal pore prevents the possibility 
 of confusion. The other structures are also affected by the extension, 
 as is shown by the fact that the marginal space free from ova, and 
 especially in front, is in such cases disproportionately large. 
 
 One might be inclined to attribute the looped arrangement of the 
 uterus primarily to the accumulation of ova in the uterus. Such is 
 not, however, the case. The loops may be observed even in imper- 
 fect development, at a time when no ova are present in the uterus. 
 They are rather the expression and result of a growth in length, 
 
THE STRUCTURE OF THE UTERUS. 703 
 
 which is disproportionate to the length of the joint. It is different 
 with the width of the uterus, which increases in proportion as the 
 eggs accumulate within it. At first so narrow that the ova can only 
 lie singly, it continues to grow, till eight, twelve, fifteen, or even more 
 can find room beside one another. It is thus easily explained how 
 the lumen of the uterus is so narrow as it is in young joints, and in 
 the lower loops, even when the joints are mature. 
 
 The wall of the uterus is formed of an apparently very extensile 
 and structureless membrane, the independence of which may be 
 clearly seen in the narrower loops, but which with, increasing width 
 becomes continually more delicate and less readily separable from the 
 surrounding connective-tissue. An epithelium, such as Stieda and 
 Moniez report, is not present, but after hardening, one can not 
 unfrequently detect on the inner surface of the cuticle the finely 
 granular residual traces of the ova. This finely granular substance 
 occurs also between the eggs, and is probably an unused remnant of 
 the yolk. 
 
 The cuticular coat of the uterus is externally surrounded by a 
 cellular layer, whose constituent elements are distinguished from the 
 ordinary connective-tissue cells by their abundant protoplasmic 
 contents, by their smaller size, and by their close grouping. In their 
 appearance and form they sometimes recall the subcuticular cells. 
 In the only moderately distended portions of the canal, they are less 
 sharply defined than in the wider parts, and are so abundantly 
 developed that Eschricht actually regarded the sheath formed by 
 them as a special organ (the capsule of the uterus). Special 
 musculature is only recognisable on the narrowed tubular portion of 
 the uterus, which connects the last loop, lying to the right or left of 
 of the cirrhus -pouch, with the female genital aperture. It consists 
 of a layer of circular muscles, which embrace the canal, and have the 
 effect of forcing the contained ova outwards. One not unfrequently 
 finds single ova still lying within the funnel-shaped opening. Their 
 transmission into this expelling apparatus, like the forward move- 
 ment through the uterus, is, apart from the vis a tergo, effected by 
 the pressure of the body-muscles, and especially by the sagittal fibres 
 which extend between the coils of the uterus, and approximate the 
 two surfaces of the joint. 
 
 Special attention must be devoted to the posterior end of the 
 uterus, which extends behind the rosette, and is formed of a coiled 
 canal, becoming ever narrower and more delicate the further it 
 extends. The upper coils appear as comparatively regularly alter- 
 nating loops (Fig. 368), but shorter and thinner than those of the 
 rosette ; inferiorly, however, the windings become more irregular in 
 
704 THE ANATOMY OF BOTIIRTOCEPHALUS LATUS. 
 
 their course, so that Eschricht described them as a special structure, 
 the so-called " knot." The canal of this coil usually contains only a 
 single row of ova, including, however, also numerous free-yolk 
 granules, which indeed are so abundant that the coil acquires thereby 
 a more or less dark appearance. This is especially true of the outer 
 end of this coil-tube, which has usually the form of a spindle-shaped 
 sac (0'06 mm.), lying sometimes to the right, sometimes to the left 
 of the middle line, and which is the portion of the uterus where the 
 eggs acquire their hard shell. This is due to the fact that the 
 terminal portion not only receives the above-mentioned (p. 701) 
 fertilising canal, but also communicates with the efferent ducts not 
 only of the ovary and of the yolk-gland, but also of the shell -gland 
 (Fig. 366). 
 
 The observation of this terminal portion is exceedingly difficult, 
 and the reports of investigators differ considerably as to its relations. 
 My enquiries have led me to conclusions which agree most closely 
 with those of Sommer and Landois ; the differences of opinion being 
 chiefly on subordinate points. They concern only the mode of con- 
 nection between the different portions, that such a connection does 
 exist, and that it is effected by the terminal portion of the uterus, has 
 been allowed by all observers since Eschricht. 
 
 The Fertilising Canal will first be considered ; as we know it 
 extends from the dilated lower end of the vagina (the receptaculum 
 seminis), and which has the function of supplying the uterus with 
 the semen necessary for the fertilisation of the ova. For this pur- 
 pose this canal affords direct communication between the receptaculum 
 and the terminal portion of the uterus. It is a comparatively short 
 duct, which describes in the median plane of the joint a curve open 
 anteriorly. The longer limb, which descends on the ventral side, and 
 first receives the semen, has only an inconsiderable thickness (0*015 
 mm.), so that it is sharply and definately separated off from the 
 receptacle. Sommer and Landois have described it it seems to me 
 erroneously as extremely delicate, since a muscular sheath is 
 distinctly recognisable. It is internally lined by a relatively compact 
 cuticular membrane. Before this descending limb reaches the point 
 where it bends round, it receives the common oviduct, just as we 
 have seen (p. 445) in the fertilising canal of Tcenia. At the same 
 time it widens, so that Sommer and Landois regard it thenceforward 
 as a direct continuation of the oviduct. Shortly after receiving the 
 latter, the fertilising canal describes the above-mentioned loop-like 
 bend, and becomes again narrower, until after a short course 
 it passes into the terminal portion of the uterus, which is dilated 
 again here. 
 
STRUCTURE OF THE SHELL-GLAND. 
 
 705 
 
 The Shell- Gland communicates with the uterus at the bend above 
 referred to. It has the form of an ovoid or spheroidal body of consider- 
 able size (0'4 mm.), and is seated 
 on the convex margin of the bend. 
 In transparent preparations it can 
 be seen even with the unaided 
 eye. It lies in the middle line, 
 below the uterine coil, just before 
 the posterior margin of the joint, 
 at a position, therefore, where the 
 yolk -gland is situated in the 
 Tcenice. This fact contributed not 
 a little to the mistake I made in 
 the first edition of this work, in 
 identifying the two structures, and 
 in regarding the shell-gland of ^ 3 69. -Female reproductive organs 
 BotllTWCephoduS as the OVary, Under f Jiothriocephalus latus, seen from the 
 ,-, ., . ,T ,-, ventral surface. Between the two ovaries 
 
 the erroneous supposition that the is geen the shell-gland. ( x 20.) 
 yolk-gland of the Tcenice produced 
 
 the eggs. Nor did the histological structure of the body seem so 
 decidedly against my opinion, for Botticher, and at first Stieda 
 also, supported the same interpretation, although they both had 
 already recognised the true ovaries in Eschricht's "lateral glands." 
 They believed that the shell-gland, which had been also described by 
 Eschricht as the " knotted gland," and regarded by him as probably 
 serving for the secretion of albumen, was the median portion of the 
 ovary. In the appendix to his first contribution, Stieda> however, 
 recognised the true nature of the body. 1 
 
 The parenchyma of the gland consists of a large number of pear- 
 shaped cells of 0*02 to 0'025 mm., enclosing clear or slightly turbid 
 contents, and each drawn out into a thin duct of considerable length. 
 The ducts are all directed inwards, and after a more or less straight 
 course, are all separately united with the loop of the fertilising canal. 
 
 It is not strictly correct to speak of this complex mass of 
 unicellular glands as a spherical body, for not only is the centre of 
 the mass which is penetrated by the efferent ducts formed of 
 ordinary connective tissue, but there are no glandular cells on the 
 
 1 Moniez has lately reproduced the old mistake, He regards the shell -gland as a 
 special median portion of the ovary ( " ovaire central "), in which, however, the ova never 
 attain maturity, but become abortive. Only the lateral ovaries produce eggs. After 
 liberation, they pass into a cavity in the parenchyma between the ovaries, are received in 
 the adjacent funnel or trumpet-like muscular end of the oviduct (" pavilion de 1'oviducte "), 
 and passed onwards. The fertilising canal and oviducts are not united with the uterus 
 till some distance from the Uterine receptacle. 
 
 2 Y 
 
706 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 
 
 anterior portion, nor where the fertilising canal joins, so that the true 
 shape is rather that of a very bulging goblet, open superiorly. 
 
 The Ovaries are, as in reality even Eschricht knew, and as is now 
 indubitably demonstrated, the so-called "lateral organs," two wing- 
 shaped structures of considerable size, which (Figs. 368 and 369) include 
 the shell-gland and the knotted-gland between them, and ascend on 
 the outside of the lower loops of the uterus. The lateral portions 
 extend to some distance beyond the median area, and the posterior 
 extremities can usually be traced close to the margin of the joint. 1 
 Like the ovaries of the Taeniadae, which they resemble in form, these 
 organs form a flat, glandular body, closely apposed to the musculature 
 of the ventral surface, and composed of numerous long, ramifying 
 caeca, spread out one beside another. This is best seen in injected 
 preparations, where the caeca are distinctly evident, in spite of 
 Moniez's denial. 2 The tubes have a thickness of about 0*03 to 
 0'04 mm., and extend in thick and short serpentine twists, so that they 
 appear as if sinuate. Especially in the upper half, where they lie 
 more closely and frequently overlap, the appearance of a composite 
 network is suggested. In such cases the course of the tubules can 
 rarely be followed for any distance, nor can their disposition be 
 definitely determined. We may, however, generally describe them as 
 radiating out in a fan-like fashion from above and from within, as is 
 especially corroborated by the fact that the lateral organs are con- 
 nected by a transverse bridge, extending in front of the lower end 
 of the receptaculum seminis. The structureless membrane which 
 bounds the tubules and this bridge externally is continued in 
 the middle line of the joint into the proper oviduct, which extends 
 backwards in a straight or slightly curved course, between the 
 receptaculum and the ventral musculature, increasing gradually in 
 width from O'Ol mm. to more than twice that, and finally opening, as 
 above mentioned, into the fertilising canal (Fig. 367). 
 
 The ripe ova, which are met with especially in the bridge-like 
 connecting portion, appear as pale, membraneless balls, measuring 
 0*018 mm. in diameter, enclosing a vesicular nucleus of 0*009 mm., 
 within which a nucleolus of 0'003 mm. can be seen. They are 
 considerably smaller in the ovarian tubules, especially towards the 
 
 1 I have never observed that, as stated by Sornmer and Landois (loc. tit., p. 20), 
 they extend beyond the posterior margin, as a flat ribbon-like appendage, reaching into the 
 next joint. Such an appearance was, indeed, occasionally seen, but a closer examination 
 showed that it was due to the overlapping of the margin of the joint. 
 
 3 Moniez denies the existence of special ovarian tubules, interpreting the appearance as 
 strands of ova, embedded without envelope between the connective-tissue cells. The eggs 
 are said to be like those of the Cestodes generally, simply modified cells of the surrounding 
 tissue (loc. cit. t p. 156). 
 
STRUCTURE OF THE OVARIES. 707 
 
 end, where they sometimes measure only O006 mm. (nucleus = 
 0-0045 mm.). 
 
 The ova pass from the oviduct into the commencement of the 
 uterus through the fertilising canal, in which they acquire their final 
 form by being equipped with yolk and shell. The fertilisation probably 
 takes place previously, during the passage through the fertilising 
 canal, as I conclude from the fact that I was but rarely able to 
 discover spermatozoa within the uterns. 
 
 The yolk-spheres, which surround the ovarian ova in large 
 numbers (from 25 to 30), are seen to be also membraneless nucleated 
 cells, having, however, a decidedly smaller size (at most O'Ol mm.), a 
 smaller nucleus (0'004 mm.), and a plasma containing numerous 
 fine and coarse granules. Eschricht correctly recognised the seat of 
 formation of these spheres in the so-called " granular heaps," which, 
 with their efferent apparatus from the yolk-gland of Bothriocephalus, 
 may be most fitly termed " yolk- vesicles." 
 
 As already noted, these structures belong to the cortical layer, in 
 which they extend in a simple close-packed layer beneath the sub- 
 cuticula (Fig. 361). They are found both on the dorsal and ventral 
 surface, but only in the lateral areas, the median region remaining for 
 the most part free. The yolk- vesicles in the middle area, especially 
 on the ventral surface, are, however, considerably larger than 
 those more peripherally situated, some of which do not measure 
 more than 0'04 mm., while the former are sometimes six or eight 
 times as large, so that they become recognisable by the unaided eye, 
 especially since their contents render them non-transparent. The other 
 yolk-vesicles are, of course, also non-transparent, but in consequence 
 of their small size, this is only expressed by the darker shade of the 
 lateral areas in which they are situated. In their form they some- 
 what recall the testicular vesicles, with which Kuchenmeister long 
 regarded them as identical. The contents and situation are, however, 
 quite different, as also the closer disposition, so close in some places 
 that the spheres coalesce. In longitudinal sections I count, like 
 Stieda, about thirty of these in transverse section, about forty-five to 
 fifty on each side on the dorsal and ventral aspect, so that the total 
 number in each joint must be near 6000, as Eschricht also estimated. 
 No special membranous boundary is recognisable. They are simply 
 collections of cells and granules, but the former have not from the 
 first, especially in young joints, their subsequent size. 
 
 Since the yolk-vesicles are destitute of distinctly independent 
 boundary, their contents can only be expelled by the contraction of 
 the body-muscles. Especially the sagittal fibres are concerned in 
 this action, for they extend between the vesicles which owe to them 
 
708 
 
 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 
 
 their form, usually ovoid, and somewhat produced inwards. The 
 external portion protruding between the subcuticular cells is thus 
 often drawn out into a conical point, which at the first glance 
 suggests the presence of an opening, which has been maintained by 
 some observers. Contrary to appearance, however, the expulsion of 
 the contents takes place at the end turned inwards, and that by 
 means of a duct, which is indeed only recognisable when it contains 
 yolk, which is by no means always the case. At first narrow and 
 inconspicuous, perhaps even without a distinct wall, these ducts 
 gradually unite to form canals, which extend between the yolk- 
 vesicles and the longitudinal muscular sheath, and finally develop 
 into a system of tubes, often conspicuous (even under a low power) 
 on the ventral surface, because of their contained yolk and wide 
 
 K 
 
 FIG. 370. Segment of BotJiriocepkalus with yolk chambers and "yellow ducts," 
 after Eschricht. ( x about 8.) 
 
 extent. Eschricht even recognised this efferent apparatus, and 
 connected it with the "granular heaps," although he, under the 
 influence of Ehrenberg's polygastric view of the Infusoria then in 
 vogue, was at first inclined to regard the latter as stomachic sacs. The 
 " yellow ducts," whose discovery so excited Eschricht that he could 
 hardly wait for the daylight in his anxiety to see them again, are 
 nothing more than the branches of this efferent apparatus, which 
 radiate outwards from the region of the so-called " knot," through the 
 median area, to the lateral portions of the ventral surface. They 
 exhibit sometimes a straighter, sometimes a more coiled course, are 
 at intervals often sinuously enlarged, and exhibit, besides, consider- 
 able variety in their degree of repletion. The walls are thin without 
 any histological differentiation, except that in the larger branches a 
 distinct membrane can be recognised. 
 
 It is a striking fact, as Eschricht rightly pointed out, that the dis- 
 
DISPOSITION OF THE GENITAL PASSAGES. 
 
 709 
 
 tribution of these yellow ducts is not exclusively confined to the 
 joint to which they properly belong, but they extend beyond it into 
 the anterior portion of the joint behind. What we have already 
 emphasised in regard to the vasa efferentia is thus true also of these 
 yolk-ducts a new proof of the correctness of the assertion that in 
 Bothriocephalus the individualism of the joints is much less perfect 
 than in Tcenia. 
 
 The disposition of the efferent ducts on the dorsal surface is much 
 more difficult to follow than on the ventral, yet it seems probable 
 that they are everywhere confined to the cortical layer, and that the 
 ramifications of the yellow ducts never traverse the central layer, but 
 extend along the sides, and in this way pass from ventral to dorsal 
 surface. The only portion of the apparatus which seems to sink 
 into the layer is the unpaired collecting tube, 
 which arises from the union of the yellow 
 ducts at the point whence they radiate out- 
 wards, and then extends inwards, penetrating 
 the muscle-layers and opening close in front 
 of the coiled gland (Fig. 371) into the fertilis- 
 ing canal. 
 
 It is in this way possible that, along with 
 the (fertilised) ova, yolk-cells also pass into 
 the terminal portion of the uterus, and that 
 both kinds of elements become enclosed in a 
 common shell. The material composing the 
 latter is a strongly refringent yellow substance, 
 which is found more or less abundantly in drops 
 between the ova and the yolk-cells. At first 
 these elements all lie near one another, with- t c _ ._ 
 out distinct order or regularity. Soon, how- 
 ever, each ovum becomes surrounded by a 
 number of yolk-cells. They thus become balls 
 of more or less considerable size, which are 
 then pressed against the adjacent drops of 
 shell-substance, so that these become here and 
 there attached to the surface as flattened or FIG. 371. Diagrammatic 
 
 4. i i , , , ml , representation of the course 
 
 Watch-glaSS Shaped drops. The Subsequent and connections of the vagina, 
 
 shell arises by the thinning and consequent as seen in longitudinal sec- 
 
 -,. P ,i in .1 tion. v.d.. vas deferens ; 
 
 spreading of the shell-substance over the c .p., cirrfms - pouch ; v. y 
 surface of the balls. While this is going on, va e ina J w '- ute 8 > ut --> 
 
 .> , -I/.1 . . -i-i I* uterine opening; /.c., fertil- 
 
 the egg has, by further inception of yolk-cells, king canal ; o.d. t oviduct ; 
 
 attained its final size, and the original, often s -9>> shell-gland. 
 
 very irregular, form becomes ovoid. Where the lid is afterwards 
 
 ut.o. 
 
710 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 
 
 situated, the shell exhibits for a while a fissure, which is closed at a 
 later stage by the application of a new portion of shell - substance, 
 which always remains isolated. The young shell is brighter and 
 thinner than it subsequently becomes, so that a staining fluid rapidly 
 affects the contents, which no longer happens in the deep - brown 
 older eggs. 
 
 Clear and distinct as the processes of oogenesis are in suitable 
 preparations, the actual mechanism eludes observation. It seema 
 plausible, however, that it is the pressure of the surrounding canal 
 which forms the eggs, though the absence of a special musculature 
 in the uterus does not seem to agree with this supposition, nor the 
 fact that the eggs in process of formation do not occur singly, one 
 behind the other, but usually in considerable numbers on the same 
 transverse section. It is possible that special protoplasmic activities 
 (amoeboid movements) play some part in the process. 
 
 The mature ova exhibit, in form and size, several more or less 
 striking peculiarities, and that quite apart from the not unfrequent 
 occurrence of malformed or stunted specimens. These variations 
 are especially noticeable in the eggs within the lower uterine 
 coils, so that it seems as if they become more uniform the longer 
 they remain within the uterus. In the rosette they have usually 
 a longer diameter of 0*05 mm., and a shorter of 0*035 mm. ; but 
 diameters of 0'056 and 0'04 respectively are also not unfrequently 
 present, so that in shape they appear sometimes more elongated, some- 
 times rounder. The lid is seldom recognisable without pressure to 
 cause it to spring up. It lies at the anterior pole, which is occa- 
 sionally somewhat flattened, and possesses a diameter of 0'013 mm. 
 (Fig. 359). 
 
 What I have noted above in regard to the reproductive organs 
 relates primarily only to the state of the ripe joints, which form, as 
 we know, the great majority in Bothriocephalus latus. In a fresh 
 specimen, measuring 720 cm. in length, the number of joints was 
 about 2400. The unripe joints are, indeed, present in considerable 
 numbers (at least 500 to 600). They are characterised by the absence 
 of hard-shelled ova, and afford in their adolescent stages a complete 
 survey of the various stages in the formation of the generative organs. 
 
 The Development of the Reproductive Organs commences with an 
 extremely simple structure. It consists, as in the Tseniadae, of an 
 aggregation of small nucleated cells, occupying the centre of the 
 joint, and but slightly separated from the surrounding parenchymal 
 cells. It is recognisable at a very short distance behind the head, so 
 that it seems probable that the differentiation of these cells has already 
 occurred in the very earliest joints. At first of inconspicuous size, 
 
DEVELOPMENT OF THE GENERATIVE ORGANS. 711 
 
 this heap of cells soon grows into the form of a longitudinal band, 
 while in the cystic tape-worms it extends transversely in correlation 
 with its subsequent structure. 
 
 This growth continues for some time without any other modifica- 
 tion. In stained preparations of the larger tape-worms (both Tcenia 
 saginata and Bothriocephalus latus) this structure is seen some centi- 
 metres behind the head, shining through the cortical layer of the 
 body. In this state the rudiment in Bothriocephalus was formerly 
 detected and examined by Eschricht. It seemed at first, however 
 and with this my account of the rudimentary reproductive organs in 
 T. saginata (p. 446) should be compared as though the rudiment 
 directly formed the efferent apparatus alone, and as though the germ- 
 producing organs originated independently, and became afterwards 
 associated with the former. 
 
 Subsequent investigations have, however, convinced me that this 
 opinion is not correct, but that the germ-producing organs also owe 
 their origin to the cells of the primitive rudiment. I can, it is true, 
 affirm this with perfect certainty only of the ovary and yolk-gland of 
 Tcenia, but the fact that the vasa efferentia, or at least their larger 
 branches, owe their origin to radiations from the vas deferens, suggests 
 that the above statement holds true also of the testes. That the genetic 
 connection between the germ-producing organs and the primitive 
 rudiment is less distinct than that between the latter and the efferent 
 ducts, as is certainly the case, is due to the fact that the latter appear 
 as more massive structures, and exhibit at an early stage a definite 
 boundary. 1 
 
 What I have to communicate with regard to Bothriocephalus in 
 this connection is unfortunately very incomplete, and indeed little 
 more than a repetition of the results of Eschricht. 
 
 I would first note that the primitive state of the reproductive 
 rudiment persists for some time without marked change. At a distance 
 of about 10 cm. behind the head, the rudiment is still seen as a dark, 
 indistinctly defined, longitudinal streak, extending in the median line of 
 the joints. Three or four centimetres farther back the contours become 
 sharper, and one can detect at the anterior end of the streak, close 
 behind the margin of the joint, a roundish aggregation of cells seated 
 on the others like a sort of head. This structure mainly represents the 
 hitherto incompletely separated rudiment of the genital ducts and the 
 associated efferent apparatus, organs whose differentiation and forma- 
 tion occupy a length of 15 cm. Fifty centimetres behind the head, 
 
 1 From this one can see how inconsistent it is for Moniez to deny the morphological 
 independence of the germ-producing organs in the Cestodes, and to refer both ova and 
 spermatozoa to the direct modification of ordinary parenchymal cells. 
 
712 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 
 
 the external genital apertures and the cirrhus-pouch can be distinctly 
 seen. All the efferent ducts extend at first in a straight direction back- 
 wards to near the posterior margin of the joint, where the rudiment of 
 the shell-gland and ovary can be distinguished between them. Both 
 originate as appendages and processes of the streak-like rudiment, 
 the shell-gland at the posterior end, the ovary at a short distance in 
 front of it, extending on either side like a pair of wings. At the same 
 time the testicular vesicles become visible in the median region of the 
 joint. They occupy for the most part the anterior clear portion of 
 the joints, while the yolk-glands, at first small and clear, are to be 
 detected somewhat farther back in the lateral areas. 
 
 FIG. 372. Development of the reproductive organs in Botkrio- 
 ccphalus latus. ( x 25.) 
 
 When the various organs have thus been mapped out, they rapidly 
 acquire their full development. Even at a distance of 60 cm. from 
 the head, the uterus, formerly but slightly looped, has, though still 
 empty, acquired essentially its final shape, except that the limbs of 
 the loops are shorter and more distinct than subsequently. Shortly 
 afterwards copulation seems to occur, for a few centimetres farther 
 back a grumous mass, penetrated by spermatozoa and balls of shell- 
 substance, is found in the posterior end of the uterus, and beside this 
 appear the first hard-shelled ova, clear and few in number. For a 
 time the ova lie in a single discontinuous row, but become by further 
 pressure more and more closely aggregated. The width of the uterine 
 canal increases, the limbs of the several loops become approximated, 
 and the appearance previously described is soon exhibited. The more 
 the eggs accumulate the darker becomes the colour of the uterus, and 
 the more distinct its definition. In older joints it appears through 
 the cortical layer as an almost blue, leaf-like lobed mass. 
 
VARIOUS ABNORMALITIES. 
 
 713 
 
 Joints not unfrequently occur in which the external coverings of 
 the uterus have been burst and the eggs liberated ; long chains of 
 open or split joints are also occasionally seen. In contrast to the 
 somewhat similar phenomenon seen in the Tcenice (p. 457), this burst- 
 ing seems here to be due in most cases to a superabundant accumula- 
 tion of ova within the uterus. The ripe joints of Bothriocephcdus 
 indeed usually liberate their contents in the normal way the ova 
 are generally found in large numbers in the faeces of the host but 
 cases are readily conceivable in which the liberation has not kept pace 
 with the production. 
 
 The Abnormalities exhibited by Bothriocephalus 
 latus include others than this bursting, which, in 
 consequence of the shortness of the joints, not un- 
 frequently appears as a distinct cleft through a 
 whole series. The doubling of the genital aper- 
 tures even is quite a common occurrence. I have 
 scarcely examined a single specimen without ob- 
 serving a greater or smaller number of adjacent 
 joints with this malformation. These segments 
 are usually further marked by their form. The 
 limiting margins are not straight, but divided in 
 the middle by a sort of step-like interruption into a 
 right and a left half, which are on different levels. 
 Portions are sometimes even separated by a furrow, 
 which extends from the middle corner of the an- FIG. 373. Series of 
 terior margin diagonally to the superior corner of J| nts with double g eni - 
 
 . 6 .-it i ,.1 T tal apertures. 
 
 the posterior margin. But even where the division 
 is not externally manifest, its presence can be readily detected by the 
 use of a compressorium. A clear line of demarcation in the direction 
 above mentioned is then observable, plainly showing that each half of 
 the joint has its special genital aperture. And more than that, one 
 can see that each of the halves is furnished with a more or less perfect 
 set of genital organs. Most distinct are the uteri, both of rosette-like 
 form as usual, except that the horns directed inwards are distinctly 
 shorter than usual. It may also happen that the two uteri are of 
 unequal size, one having grown at the expense of the other. As with 
 the internal uterine horns, so also the other portions directed towards 
 the middle line are atrophied. One cannot, however, deny that a true 
 duplication has taken place, that there is really a double chain, whose 
 joints have united by their adjacent margins, with concomitant degene- 
 ration of the approximated lateral areas. That the joints are wedged 
 alternately into one another is of subordinate morphological impor- 
 tance. This condition is genetically explained, and indeed the whole 
 
714 OCCURRENCE AND DEVELOPMENT OF BOTIIRIOCEPHALUS LATUS. 
 
 malformation, so far as my researches go, by the interpolation of a 
 half (sometimes only imperfectly separated) joint. This is again re- 
 peated, as the adjoining figure shows. The second half joint, of course, 
 belongs to the opposite side. 
 
 Occurrence, and Development of Bothriocephalus latus. 
 
 Knoch, " Die Naturgeschichte d. breiten Bandwurmes mit besond. Beriicksichtigung 
 seiner EntwickelungPgeschichte. " M6m. Acad. Sci. St. Petersb., t. v., 1862. 
 
 Knoch, "Neue Beitrage zur Embryologie dea Bothriocephalus latus." Bull. Acad. 
 imptr. St. Petersb., t. xiv., p. 178, 1869. 
 
 Leuckart, " Die menschlichen Parasiten," 1 eA, Bd. i. f p. 757, Bd. ii., p. 867, 1863. 
 
 Bertolus, "Sur le developpement du Bothrioce'phale de rhomme." Comptes rendus, 
 t. Ivii., p. 569, 1863. 
 
 Braun, " Zur Entwickelungeschichte des breiten Bandwurmes : " Wiirzburg, 1883. 
 
 Schauinsland, " Die embryonale Entwicklung der Bothriocephalen.' Jenaische 
 Zeitschr.f. Natunoiu., Bd. xix., 1885. 
 
 The problem of the occurrence and development of Bothriocephalus 
 latus has only received satisfactory solution during the last few years. 
 Since this tape-worm is found especially in districts where water is 
 very abundant, and since the nearest relations of this worm are found 
 mostly in aquatic animals, the opinion has been for long expressed 
 that the intermediate host of this parasite was some aquatic animal, 
 which transmitted it in its young stage to man. Fishes were first 
 thought of, and it was sometimes supposed that the delicate trout and 
 salmon were the hidden homes of the Bothriocephalus embryos. 
 
 The probability was increased, when Schubart of Utrecht, accord- 
 ing to a communication of Kolliker's, 1 developed the ova of this tape- 
 worm in water, and observed the liberated embryo with its mantle of 
 cilia. Schubart's observations were unfortunately not published in 
 detail. 2 They would perhaps have been forgotten, had not similar 
 investigations, twelve years later, pursued contemporaneously in 
 Eussia, France, and Germany, by Knoch, Bertolus, and myself, led 
 essentially to the same results. All agreed that the development of 
 the embryo occupied usually several months, varying with external 
 conditions, and especially with the temperature. The liberation only 
 occurs during the warm season, so that ova formed in September are 
 not liberated till April of the next year. Except in the ciliated 
 envelope, which surrounds them at some distance, the embryos essen- 
 tially resemble the long-known embryos of Tcenice, especially in 
 bearing the characteristic hook-apparatus. 
 
 1 Zeitschr. f. wiss. Zool., Bd. iil, p. 86, 1851. 
 
 2 The reports which Verloren gave at the Assembly of Naturalists at Bonn (Tage- 
 blatt, p. 19, 1855) as to the observations of his deceased friend, do not really extend the 
 communications of Kolliker except in expressly tracing the ciliated embryos to Bothrio- 
 cephalus latus. 
 
HISTOKICAL SKETCH OF OUR KNOWLEDGE. 
 
 715 
 
 FIG. 374. Free-swimming embryo 
 
 It was then established by Bertolus and myself that the ciliated 
 embryos of Bothrioceplialus latus, like those of other forms since dis- 
 covered, serve just as do the similarly 
 ciliated embryos of Distomum for 
 enabling the free embryo to migrate 
 into a temporary host, in which the 
 further development to a cysticercoid 
 intermediate form occurs. This, of 
 course, suggested aquatic animals, 
 having the same habitat as the free- 
 swimming embryo. That fishes were 
 thought the most likely subjects is not 
 surprising, since these are not only the 
 most frequent prey of all aquatic 
 animals, but also because in the flesh 
 and viscera of fishes Cestode larvae had 
 
 r* ,1 , p , of Bothriocephalus lotus. ( x 600.) 
 
 not unirequently been round encap- 
 suled, which, from the structure of their heads and other organs, might 
 be young stages of Bothriocephali. In fact, Bertolus did not hesitate to 
 claim as the intermediate form of B. latus one of these larvae described 
 by Eudolphi as Ligula nodosa, and parasitic in various Salmonidae. 
 
 The reasons which Bertolus gave for his opinion were, indeed, 
 scarcely sufficient to establish the connection of the two forms ; and that 
 the less since Ligula nodosa is a parasite of a very debateable character. * 
 We were, however, led to attempt a solution of the problem experi- 
 mentally. For this purpose, with the consent of the owner, I put a 
 large quantity of ova and free-swimming 
 embryos, enough to infect hundreds of fish, 
 into a trout-stream 2 near my home, then in 
 Giessen. The result was unfortunately nega- 
 tive, all the trout which I examined in all 
 more than two dozen at various intervals up to 
 two months after the introduction of the em- 
 bryos, were free from the expected parasites. 
 Similar experiments on certain species of 
 Cyprinus also failed. The fact, which I then from the smelt 
 learned, that Botticher had, in a post mortem 
 
 examination of a woman who had died in poor circumstances at 
 Dorpat, and who had for weeks before her death eaten neither fish 
 nor flesh, found almost a hundred Bothriocephali, which, except one 
 about a yard long, only measured a few inches, and must therefore 
 
 1 Diesing regards it (" Revision der Cephalocotyleen, Abtheilung Paramecotyleen," 
 Sitzungsb. d. Tc. Wiener Acad., Bd. xlviii., p. 232) as a separate portion of Tricenophorus. 
 
 2 First German edition of this work, Bd. ii., p. 867. 
 
 FIG. 375. Encapsuled 
 larva of a Boihriocephalus 
 (x about 
 
716 OCCURRENCE AND DEVELOPMENT OF BOTHRIOCEPHALUS LATUS. 
 
 have found their way thither not long before, 1 led me to think that not 
 fishes, but perhaps smaller aquatic animals, such as Naiadse, which 
 harbour the related tape-worm Archigetes, might be the intermediate 
 hosts of Bothriocephalm. 
 
 In opposition to Bertolus and myself, Knoch lays but little stress 
 in the process of infection on the ciliated embryos. He attributes to 
 them only the rdle of increasing the range of distribution, and 
 facilitating the transmission of the embryo. From his feeding 
 experiments, he concludes that this ciliated stage is not necessary in 
 the life-history of the parasite. Infection is effected equally well, and 
 indeed more frequently, by eggs, and it is indifferent whether these 
 contain an embryo or not. It occurs, as in the Tcenice, even when 
 proglottides with ova are conveyed to the alimentary canal of the 
 future host. There is no change of host, the transmission of the ova 
 is directly followed by the development of the sexually mature form, 
 so that man acquires the Bothriocephcdus, not from fishes or lower 
 animals, but directly from eggs or embryos which he has swallowed, 
 usually in drinking water. 
 
 In support of these assertions, Knoch cites, as we have said, the 
 results of the experiments made by him on dogs and other mammals. 
 In seven different cases these were fed partly with ova, and the 
 associated proglottides, partly with the ciliated embryos. Investiga- 
 tion of the victim, sometimes after several weeks, sometimes only after 
 months had elapsed, gave in three cases (in a dog, 
 a cat, and a rabbit) entirely negative results. 
 In the other instances, which were all dogs, 
 Botkriocephali were found in the gut, but only 
 a few (at most seven, and in one experiment, 
 made by Pelican, only one), and these at very 
 different stages. Although the number of parasites 
 contrasted strikingly with the hundreds and 
 thousands of ova used for feeding, and although 
 the degree of development did not seem to agree 
 with the period which had elapsed, Knoch was 
 ture ova. After Knoch so convinced of the cogency of his experiments, 
 that he forthwith declared the result as requir- 
 ing no further confirmation. And this opinion persisted even till a 
 time when I had for long emphasised the insufficiency and the 
 inadmissibility both of the proof and of the method of experiment, 
 noting that the dog under ordinary circumstances can by no means 
 be regarded as free from Bothriocephali, as was asserted by Knoch, 
 but is, on the contrary, according to both older and more modern 
 
 Sitzsb. Dorpater Gcs. f. Naturw., Feb. 1871. 
 
THE EXPERIMENTS OF KNOCK. 
 
 717 
 
 helminthologists (Linne, Pallas, and Krabbe) infected by them in all 
 localities where the parasite abundantly occurs. 
 
 It is now unnecessary to criticise in detail 1 these statements 
 maintained by Knoch with so much confidence, yet it is perhaps not 
 superfluous to remember that the long period of incubation, and the 
 character of the embryos, are facts which Knoch had opportunity 
 enough to observe, and are of themselves enough to cast doubt upon 
 his results, nor have I, though sufficiently convinced, omitted to 
 repeat Knoch's experiments. In Giessen, where there are no Bothrio- 
 cephali, I have not only experimented on dogs, both young and old, 
 with fresh ova and with ciliated embryos, but have, along with 
 several of my pupils (more than eight persons), swallowed each a 
 dozen embryos, without ever obtaining anything but a negative 
 result. 2 
 
 Eecent progress has thoroughly justified my opposition to Knoch, 
 
 fl 
 
 and it has meantime been experimentally proved 
 
 by Braun that Bothriocephalus latus has an inter- c 
 
 mediate host, in which alone its development is 
 
 perfected. This intermediate host is a fish, and 
 
 especially the pike, an animal which, according to 
 
 Braun's researches in Dorpat (long known as a home 
 
 of Bothriocephalus), so frequently contains larval 
 
 forms of this parasite, that among the specimens 
 
 from the Peipus, the Wirzjaw, and the Eubach, it 
 
 is very rarely that one is found without parasites. FlG - 377. Larvw 
 
 rri A> i 11 i ,1 of Bothnocephalus 
 
 The worms are found encapsuled, not only in the latus from the 
 most varied positions in the viscera, but also in the P\ k - A a , nd # 
 
 i j n -j T_i 1. Wlth extended, O 
 
 muscles, and usually in considerable numbers, so with contracted 
 
 that pikes of little more than a span long some- 
 times contain in the flesh alone thirty or more. 
 
 The pike, though the favourite, is not the only host of this worm. 
 It occurs also, according to Braun, in the burbot (Lota vulgaris), in the 
 same organs as in the pike, but less constantly and less abundantly. 
 It is possible, further, that in course of time we shall become 
 acquainted with other fish which are intermediate hosts of this 
 Bothriocephalus. 3 
 
 1 See also my remarks published at the time (loc. cit.), and also the criticism of 
 Braun (loc. cit., pp. 6-12). 
 
 2 Loc. cit., Th. i., p. 764 ; Th. ii,, p. 867. 
 
 3 Thus Dr. J. Ijima, Tokio, informs me that in Japan, where Bothriocephalus is fre- 
 quent, the pike hardly ever occurs. He conjectures that the cystic form is harboured in the 
 species of salmon (Onchorhynchus Huberi and 0. Pcrryi), which are eaten not only salted 
 and fried, but in certain districts raw in sauce, like bonettas, mackerel, plaice, carp, &c. 
 Fish form an important constituent of food throughout Japan, 
 
718 OCCURRENCE AND DEVELOPMENT OF BOTHRIOCEPUALUS LATUS. 
 
 As found in the pike, the worm is long and narrow, not flat, 
 however, but somewhat round and distended. 1 It varies in length 
 from 1 to 2*5 cm., and in breadth from 2 to 3 mm. When much 
 contracted, the body assumes, of course, a more compact form, the 
 longitudinal diameter becoming reduced by more than half, and 
 the thickness increasing in proportion. This is especially seen in 
 front, where the head, as seems always the case in the pike, 
 is invaginated, so that the subsequent external surface is wholly 
 turned inwards, bounding a narrow irregular cavity, which begins 
 with a distinct depression in the middle of the anterior end, 
 and is about 0*5 mm. deep. If the parasites be put into luke-warm 
 water, salt solution, albumen, or gastric juice, and kept at the 
 temperature of an incubating apparatus, the head is usually evaginated. 
 It appears as a more or less club-shaped or glandiform top, hardly 
 1 mm. in length, bearing on each of the sides which correspond to the 
 greater transverse diameter of the body a rather shallow suctorial 
 groove, thus agreeing essentially with the head of the 
 future Bothriocephalm. Like the head end, so also the 
 rounded thin posterior extremity is not unfrequently 
 retracted, though only of course to the extent of a small 
 inconspicuous depression. There is, as we should expect, 
 d priori, no trace of a proper caudal bladder (see p. 377). 
 The body throughout its whole extent is solid, and in 
 structure essentially similar to the adult, but without 
 reproductive organs, and without segmentation, although 
 transverse wrinkles produce at first sight a similar 
 impression. In comparison with the adult Bothrio- 
 cephalus, the multitude of calcareous corpuscles is very 
 striking ; they are almost uniformly distributed through 
 the body, and in such numbers that the larvae when fresh 
 appear almost white. In moist warmth the worm makes 
 very energetic movements. Not only is the head 
 repeatedly protruded and retracted, while one wave of 
 FIG. 378. contraction after another passes over the body, but the 
 Larva of worm bends and straightens alternately like a whip, and 
 
 Bothrioceph- ,, , -. - 
 
 alus latus, tne head presents many changes in form and general 
 with protm- appearance. 
 
 ded head. ( x mi , , , 
 
 6.) -Ihe capsule round the worm is not at all firm, 
 
 so that not unfrequently, especially on the intestinal 
 
 wall, the worms are seen with one end projecting into the body- 
 
 1 Through the kindness of Prof. Braun, I have been enabled to examine a large 
 number of bladder-worms from the pike, and resulting Bothriocephali of different sizes, 
 for which I feel constrained to express my gratitude here. 
 
 Bafl 
 
 m 
 
THE EXPERIMENTS OF BEAUN. 719 
 
 cavity, or quite free within the latter. Under favourable circum- 
 stances they may be kept alive as long as eight days outside their host. 
 Such were the forms which Braun experimentally demonstrated 
 to be the young stages of B. latus. He experimented first with cats 
 and dogs, in which the absence of Bothriocephalus was carefully proved 
 beforehand by examination of the faeces and the administration of 
 anthelminthics. The animals (seven cats and nine dogs) were each 
 infected with a definite number of larvae, which were mixed with the 
 carefully inspected food. The examination of the host took place at 
 various periods, after some days or some weeks. Only in two cases, 
 in a cat and in a dog, was the result thoroughly negative. In a third 
 case of a cat, which in consequence of repeated treatment with 
 kamala and castor oil, was affected with enteritis, there was found in 
 the thick intestinal mucus a single Bothriocephalus, little modified, but 
 still living, though with the posterior end somewhat lacerated. In all 
 the other cases, however, tape- worms were found, in numbers varying 
 
 FIG. 379. Young Bothriocephali FIG. 380. Head of a Bothrio- 
 
 from the intestine of the cat, after cephalus reared in the cat from 
 
 feeding with bladder-worms from bladder-worms from the pike, after 
 
 the pike (nat. size). Braun. (x36.) 
 
 with the abundance of the feeding, and at degrees of development 
 corresponding to the periods which had elapsed since infection. A 
 dog which was still sucking, and which had been fed with seventeen 
 bladder-worms, exhibited, ten days later, fifteen tape-worms, which, 
 in spite of the absence of reproductive organs and their small size 
 (from 9 to 14 cm. in length), were undeniably specimens of B. latus. 
 In another case, in which the animal (a cat), after an interval of six 
 or seven weeks, was again fed with flesh of the pike and burbot 
 till the examination ten days afterwards, three Bothriocephali were 
 found in the gut, half a metre long and six or seven weeks old, with 
 at least 400 joints, of which the last exhibited almost mature repro- 
 ductive organs and eggs within the uterus ; but besides these were 
 
720 OCCURRENCE AND DEVELOPMENT OF BOTIIRIOCEPHALUS LATUS. 
 
 found a large number of smaller worms at various stages of development 
 (one to ten days old). The smallest differed from the Bothriocephali 
 of the pike used for feeding, only in the constant evagination of the 
 head, while the largest, measuring 15 cm. in length, already exhibited 
 a distinct segmentation, though no reproductive organs were recognis- 
 able to the naked eye. The size of the others varied from 2 to 8 cm. 
 
 Not only in the dog and cat, however, but also in man, successful 
 experiments led to positive results. 
 
 The experiments were made on three of Braun's students in 
 Dorpat, who volunteered for the purpose. None of them had ever 
 suffered from Bothriocephalus, nor did any one expel ova of Bothrio- 
 cephalus at the commencement of the experiment. In the end of 
 October, two of them (A and B) swallowed three, and one of them (C) 
 four, freshly removed Bothriocephalus larvae in milk, sausage, or bread, 
 After the lapse of a month, 30 to 40 ova of Bothriocephalus were 
 found in the first preparation made from the faeces of each, while 
 eight days previously slight intestinal pains had been felt, which 
 were due to the growing worm. The expulsion, which was brought 
 about a few days after, resulted in the case of A in two Bothrio- 
 cephali, in the case of C in three, and in the case of B in a number of 
 fragments, which probably originated from several specimens. The 
 average length of the worms was estimated at about 335 cm., the 
 average number of joints at 1209, so that the growth of the worm day 
 by day must, on an average, have resulted in a length of about 
 8 - 8 cm., representing thirty-one or thirty-two proglottides of average 
 size. Since, however, the growth takes place at the anterior end, 
 where the joints are mostly very small, the number produced daily 
 must be much greater than Braun computes. Thus it is also 
 explained how the worm, with increasing age, attains an ever greater 
 length. During their four weeks' growth the worms had liberated no 
 proglottides, as was also evident from the character of the terminal 
 joint, which had an elongated tongue-like form, instead of the more or 
 less degenerate semicircular form, which is exhibited in other cases 
 as the result of a separation of the joints which does not anatomically 
 coincide with the boundary of the segment. 
 
 In comparing this tape-worm reared in man with that from the 
 cat, one is struck by the fact that the former has, in a shorter time, 
 grown much larger, and formed far more joints than the latter. Nor 
 is this true only of the general structure, but also of the individual 
 parts. The head of the worm from the cat is markedly smaller, the 
 anterior portion of the body extended and thin, the rest of the chain 
 narrow and lean, and composed of joints which are for the most part 
 much elongated. There cannot, however, be any doubt as to the rela- 
 
INITIAL STAGES OF DEVELOPMENT. 721 
 
 tionship of the worms. The differences evidently result from differ- 
 ences in the hosts, and similar instances are found in the case of 
 other parasites. The BotJiriocepJiali found normally in the dog are also 
 (according to Braun) far inferior to those of man, both in length and 
 thickness. The head only measures a third of the usual size, the 
 joints are smaller and flat, and in some cases thinner than in the 
 above-mentioned Bothriocephali from the cat. 
 
 Satisfactory as are the conclusions to be drawn from such experi- 
 ments, our knowledge as to the actual progress of development is still 
 very incomplete. 
 
 Only the processes of formation of the embryo are really known, 
 which have been recently elucidated by the work of Schauinsland 
 above referred to. 
 
 We have already (p. 321) noted that the mature eggs of Bothrio- 
 cephalus latus include within the ovum proper a large quantity of 
 granular yolk-cells, and are surrounded by a hard shell 
 with an operculum. The germinal vesicle, hidden amid 
 the yolk mass, is rarely visible without special treat- 
 ment, at least after the shell has become quite brown. 
 When the eggs are laid they have generally already 
 passed through the first stages of development. Under 
 favourable circumstances, a clear spot can be seen FIG. 381. Ovum 
 through the shell amid the yolk spheres, which gradu- ^^h^yoik' 
 ally increases to form the rudiment of the embryo. cells and shell. ( x 
 The yolk-cells, as is well known, take no direct share 
 in the formation of the latter. They persist for a while unmodified, 
 and then, breaking up, are absorbed as nutritive material by the cells 
 of the embryo. 
 
 The first changes in the ovum have not been observed. From 
 subsequent processes, however, they seem to consist in a segmentation 
 which after the first cleavage into two becomes unequal, resulting in 
 products which differ in position and appearance. The one set are 
 the true embryonic cells. At first, four in number, they occupy as 
 before the middle of the ovum, while the others, also few in number, 
 become separated off, pass through the surrounding yolk-cells to the 
 surface, and there form by flattening and peripheral coalescence a thin, 
 clear, enveloping membrane, which persists for a time, and is some- 
 times recognisable, along with the remnants of the yolk, even till the 
 liberation of the embryo. There can be little doubt that these en- 
 veloping cells represent the covering cells which have been already 
 mentioned in connection with the cystic tape-worms, and which van 
 Beneden 1 has since described in the development of the Tcenice as 
 
 1 Archives de Bid., t. ii., p. 185, 1881. 
 2 Z 
 
722 OCCURRENCE AND DEVELOPMENT OF BOTHRIOCEPHALUS LATUS. 
 
 " cellules albuminogenes." But the four embryonic cells lying inside 
 the yolk are not all of the same nature. There is one among them 
 which is seated as a cap upon the others, and which pursues a separate 
 
 FIG. 382. Ovum of Bothriocephalus 
 latus, after Schauinsland, with four 
 embryonic cells and enveloping cells 
 on the granular yolk ( x 600). 
 
 Fio. 383. Another ovum, with 
 covering cells apposed to the em- 
 bryonic body. ( x 600. ) 
 
 course, inasmuch as, instead of dividing further along with the others 
 and helping to form the embryo, it grows round them, and, along with 
 its descendants, is gradually modified in the 
 course of time into the ciliated mantle. As van 
 Beneden has observed and I can now confirm 
 the statement the chitinous shell surrounding 
 the embryo of Tcenia originates in exactly the 
 same way. It is the result not of a simple 
 secretion, but of a number of cells (" cellules 
 chitinogenes "), which at an early stage 
 separate from the rest and grow round them 
 in the form of a pellucid membrane, which 
 gradually thickens, and is modified into 
 the subsequent shell. The ciliated membrane 
 of the Bothriocephali is thus morphologically 
 equivalent to the firm egg-shell of the cystic 
 tape- worms and the associated egg-membrane, 
 but not, as I formerly (p. 326) believed, to the 
 peripheral border cells. There is, indeed, 
 both anatomically and physiologically, a con- 
 siderable difference between the two organs. 
 From the originally thin and transparent 
 envelope there arises no thick and firm 
 
 FIG. 384. Egg of Both- 
 riocephalus, with imperfectly 
 developed embryo, being ex- 
 pelled by compression. In 
 the interior of the egg-shell 
 are seen the remains of the 
 yolk-cells, and the enveloping 
 membrane with its nuclei. 
 (AfterSohauinsland.) 
 
 chitinous shell, but a soft membrane, which, by the separation of 
 the primarily closely apposed cell- walls, is divided, at a somewhat 
 
ORIGIN OF THE CILIATED MANTLE. 
 
 723 
 
 early stage, into two concentric lamellae, between which lie a 
 number of coarse-grained protoplasmic masses, with numerous, some- 
 what large nuclei, which owe their origin to the multiplication of the 
 few originally present. Thus the ciliated mantle does not consist, 
 as formerly supposed, of a simple membrane, but of a double one, 
 as has since been independently discovered by Schauinsland and my- 
 self. Even at a very early stage may be detected short and delicate 
 ciliated hairs on the external membrane, but these do not become 
 very distinctly visible till after some time, when they have considerably 
 increased in size. 
 
 But while the mantle has originated in the manner which we have 
 thus shortly described, the nucleated mass of embryonal cells in its 
 interior has been transformed by continuous en- 
 largement and cell division into a clear solid body 
 of round form, which is somewhat sharply defined, 
 and which may be recognised as the true embryo 
 by the rapid increase of the primary cilia. 
 And this is still more evident from the fact that 
 in the meantime the yolk-cells surrounding the 
 mantle have, for the most part, entirely broken up, 
 and, except numerous granules, have only left 
 some larger or smaller irregular drops. One may 
 occasionally still recognise some altered yolk-cells, with fluid contents, 
 and with few granules. 
 
 When the development has progressed further, the previously 
 visible motions of the embryo become more marked. The body 
 
 FIG. 385. Embryo 
 otBothriocephalus latus 
 in the egg. 
 
 FIG. 386. Free ciliated embryos of BothriocepTialus latus. ( x 500. ) 
 
 shortens and lengthens alternately, and the hooks are moved, until 
 the lid opens and affords an exit. In slipping out, the body and its 
 
724 OCCURRENCE AND DEVELOPMENT OF BOTHRIOCEPHALUS LATUS. 
 
 mantle are squeezed through the narrow opening, and the play of the 
 ciliated hairs begins, if it have not previously begun in the interior of 
 the egg. The liberated embryo immediately resumes its round form, 
 and swims about in the water by means of its cilia, rotating continu- 
 ally on its axis, with the hooks directed backwards. The cilia are 
 extremely thin and delicate, and can only be recognised to their full 
 extent in a good light. They are disposed very close to each other, 
 and in contradistinction to the other species (Fig. 386), and also to 
 Knoch's description, are of so considerable a length that they exceed 
 the diameter of the embryonal body. In the interior of the egg-shell 
 one usually sees, besides the remains of the yolk-cells, the nucleated 
 enveloping membrane. 
 
 The period of incubation is extremely variable, being determined 
 by the surrounding temperature and the depth of the water. In 
 the middle of summer, when the eggs had been kept in flat saucers, I 
 have often seen the embryos escape before the end of a month, and 
 in the incubator, with a temperature of 37'5 C., after fourteen days. 
 Under other circumstances, several months, or if the winter intervene, 
 many months (eight or more), may elapse before the embryos are 
 hatched, even when the extent of their development suggests that they 
 should have come out some time previously. 
 
 In the free state the embryos continue to live and move for some 
 days, sometimes more than a week. By means of their cilia they 
 swim constantly, but somewhat slowly and heavily, through the water. 
 The form of the body is but little altered, though sometimes rather 
 elongated and sometimes shortened, so that the poles become flat- 
 tened, or there may even be formed a slight pit or depression. This 
 is especially true of the anterior bookless pole, which during strong 
 contraction is broader than the posterior. After a short time the 
 two lamellae of the mantle separate considerably from each other owing 
 to the inception of water. The mass enclosed between them becomes 
 consequently clearer and more transparent, and the nuclei, formerly 
 so numerous, disappear. In place of these, however, it now appears 
 (Fig. 386, B) as though the space between the lamellae were occupied 
 by clear vesicular spaces, closely arranged in a single layer, so that they 
 flatten out almost prismatically at the points of contact, and squeeze 
 between them the granules which were originally more equally dis- 
 tributed throughout the whole mass. I have previously (p. 329) inter- 
 preted these vesicles without hesitation as cells, as Bertolus had also 
 done, but now I find myself compelled to modify my opinion, and to 
 regard them as vacuoles, which have probably arisen simply in conse- 
 quence of the absorption of water. In this interpretation I differ on 
 the whole but little from Schauinsland, who refers this appearance of 
 
STRUCTURE OF THE FREE-SWIMMING EMBRYO. 
 
 725 
 
 FIG. 387. Free-swimming embryo of 
 BothriocepJialus latus with the protoplas- 
 mic threads between the body and the 
 ciliated mantle. (After Schauinsland.) 
 
 the embryos to the presence of protoplasmic threads, which extend in 
 
 regular order between the two lamellae, and thereby simulate cells. 
 
 Just as the two lamellae of the mantle 
 
 are connected with one another by 
 
 threads, so, too, do threads connect 
 
 the embryo with the mantle, but the 
 
 latter are considerably fewer in 
 
 number and less strongly developed 
 
 (Schauinsland). They are best seen 
 
 in embryos which have lived for 
 
 some length of time in the water, 
 
 and in which the space below the 
 
 mantle has been enlarged by the 
 
 absorption of water. In the in- 
 terior of the embryonic body, which 
 
 has a diameter of 0'045 mm., and is 
 
 thus considerably larger than that of 
 
 the human bladder- worm, one recog- 
 nises in successful preparations not 
 
 merely the fibrous strands which are inserted on the roots of the hooks 
 and move the latter, but also a tissue of very vesicular cells, which is 
 surrounded on all sides by smaller cells, and occupies especially the 
 hookless half. This does not consist, however, of a simple connected 
 mass, but is divided into four adjacent balls by the fibres and cortical 
 cells which insinuate themselves into it. The hooks themselves are 
 strongly developed (O015 mm. in length), and provided at the ends 
 with a sharply defined sickle-like claw, 0*006 mm. 
 
 The longer the embryo lives freely, and the more the mantle 
 becomes inflated, the more do the em- 
 bedded granules disappear. In the same 
 way, the activity of the cilia decreases 
 and the motion becomes slower. At last 
 the embryo sinks to the ground. The 
 ciliary activity ceases, but the move- 
 ments of the hooks and the contractions 
 of the body may still be observed for 
 some time. In many cases, however, the 
 mantle has already been stripped off, so 
 that the embryo is now completely free, 
 and moves about with lively movements 
 of the hooks and of the body. It not un- 
 frequently happens that while the embryo 
 is escaping, only the external lamella of the mantle is rent, and in 
 
 FIG. 388. Embryo of Bothrio- 
 cepJialus latus escaping from its 
 ciliated envelope. 
 
726 OCCURRENCE AND DEVELOPMENT OF BOTHRIOCEPIIALUS IATUS. 
 
 such cases the inner one remains for a time in connection with the 
 embryo in the form of a distinct delicate skin, presenting the appear- 
 ance of a clear albuminous layer (Fig. 388). It is difficult to deter- 
 mine how long the worm can continue in this free condition without 
 the mantle. Its appearance is for some time so thoroughly normal, 
 and its mobility so great and constant, that I cannot agree with Knoch, 
 who is inclined to regard the bursting of the mantle and the issue of 
 the embryo as signs of a miscarriage. On the contrary, I should con- 
 sider it probable that, as in the ciliated embryos of the Trematodes, 
 this event takes place when the animals enter their intermediate host. 
 If my opinion be correct, the ciliated coat is of use only in the search 
 for the latter. For the embryos do not enter the tissue of their host 
 from the intestine, but make their way directly into it from without, 
 and in so doing they are much aided by the powerful movements 
 of the hooks and of the whole body. 
 
 This process has unfortunately hitherto quite escaped observa- 
 tion. All attempts to bring about an immigration of the embryos of 
 Bothriocephalus have failed. I have several times kept young pike 
 for a week in the same aquarium with ciliated embryos without 
 infection taking place. Just as unsuccessful were the experiments of 
 Schauinsland, who several times, by means of a pipette, introduced a 
 large number of ciliated embryos into the stomachs of young burbots, 
 but could not find that they had bored into the walls of the intestine, 
 or even pierced them. Twenty-four hours later they were found 
 usually still living, and for the most part still surrounded by their 
 cilia, chiefly among the pyloric caeca. 1 
 
 These negative results are the more striking because it has been 
 certainly demonstrated that pike and burbot are the intermediate 
 hosts of Bothriocephalus. Whether the animals experimented upon 
 were already too old for infection, or whether the embryos migrate, 
 in the first place, into other aquatic animals, perhaps invertebrates, 
 which are subsequently eaten by the fish when their inmates have 
 attained a certain stage of development, are in the meantime open 
 questions, which can only be answered by further investigations. 
 The conditions of development in Trematodes, to which we have 
 already referred, seem to favour the latter supposition; and that 
 all the more since the larvae of Bothriocephalus in the pike 
 and burbot were never observed by Braun in the first stages of 
 development, and were always of a definite size (8 to 10 mm.). 
 Braun, who inclines to the same opinion, advances a number of 
 further observations in its favour. He finds that the larvae are 
 specially numerous in the wall of the intestine, and has observed 
 
 1 Loc. cit., p. 26. 
 
METAMORPHOSIS OF THE EMBRYO. 
 
 727 
 
 some partly projecting out of it, and others free in the body-cavity, 
 from which he concludes that it is possible that they reach the in- 
 testinal canal along with the first intermediate host, and that, after 
 being liberated by the digestive process, bore through the intestinal 
 wall and wander further. 1 
 
 This being so, we are left to mere conjectures in regard to the 
 changes which the six-hooked embryo undergoes in assuming its 
 subsequent larval form. It seems probable, as we have already noted 
 (p. 377), that the embryo, after migrating into its host, increases in 
 size, loses its hooks, draws in one of the poles in order to form the 
 head, and by continuous longitudinal extension grows into the sub- 
 sequent larva. If the larval life of the worm be really divided between 
 two intermediate hosts, these modifications will probably take place 
 in the first, so that the second will only affect the parasite in so far 
 as it affords the possibility of further growth. 
 
 If our views regarding the metamorphosis of the embryo of 
 Bothriocephalus be correct, the larva which is formed from the latter 
 represents a stage which we are quite justified in describing as 
 " cystic." It is true that the bladder and head-rudiment exhibit 
 very striking differences in form and structure when compared with 
 those of others, say of the bladder-worm of the pig ; but this need not 
 at all affect our conclusion, since the nearest relatives of the true 
 bladder-worms often present similar variations. We need only com- 
 pare with these worms the above described Piestocystis, to see in their 
 proper light the relations which exist between them. In both we 
 find a solid, somewhat elongated, worm-like body, whose develop- 
 ment from the six-hooked embryo can hardly be doubted, and in both 
 
 FIG. 389. Young 
 bladder-worm from the 
 pike, with invaginated 
 head. ( x 6.) 
 
 FIG. 390. Head of bladder-worm from the 
 pike. A, In longitudinal section; -B, In cross 
 section. ( x 40.) 
 
 a retracted head without any sharp demarcation from the rest of the 
 body. The fact that this head is still less individualised than in 
 
 1 Loc. cit., p. 50. 
 
728 OCCURRENCE AND DEVELOPMENT OF BOTIIRIOCEPHALUS LATUS. 
 
 Piestocystis, is explained by the absence of the muscular suckers, which 
 are so specifically characteristic of the head of Tcenia. And the fact 
 that in place of the four transversely placed suctorial grooves only 
 two occur in Bothrioccphalus, is also explicable ; for it can be easily 
 proved by means of sections that the invaginated head of the bladder- 
 worm from the pike at first appears 
 only as a flattened cavity, which is 
 lined by a continuation of the cuticle, 
 and which, extending in the direction 
 of the shortest diameter (i.e. at right 
 angles to the broad surface), sinks in 
 for some distance from the anterior 
 end of the body. Only after more 
 minute observation does one perceive 
 around the cavity (especially in 
 
 FIG. 391. Transverse section through 
 the body of a larva of Bothriocephalus. 
 
 transverse section) the parenchyma of the invaginated head with its 
 muscular fibres, which form externally a sort of receptaculum, dis- 
 tinctly separating the head from the rest of the body. On the right 
 and left, close to the receptaculum, one can now 
 distinguish the lateral nerve cords. 
 
 How this larva changes into the jointed tape- 
 worm after its transference to the final host has not 
 yet been investigated. Braun's observations, which 
 alone are available on this point, only show that, 
 soon after entering the digestive apparatus of the 
 final host, the larva stretches out the hitherto 
 retracted head, and fastens itself by its aid to the 
 intestinal wall ; and that, after losing the calcareous 
 corpuscles, which were previously very numerous, 
 it grows with considerable rapidity, so that in a few 
 days it may measure 6 cm. in size, and exhibit a 
 somewhat indistinct segmentation. The increase in 
 size affects not only the body, but also, and perhaps 
 FIG. 392. Sa- sooner, the head, whose form at the same time is 
 
 tTe more definite, and like that of the adult worm, 
 protruded head of a Whether the larval body is entirely or partially 
 
 bladder-worm from ,.-,. . i . mi i 
 
 the pike, (x 40.) l s t during this modincation is uncertain. Ine cle- 
 This section is taken scription given by Braun almost leads us to infer the 
 
 to one side of the G ,^, J . . , . , ,. . , 
 
 middle line, so that contrary, although in his observations no special 
 the lips of the sue- attention seems to have been directed to the history 
 
 tonal pits limit the , , , ., . . . . , 
 
 latter externally. of the larval body. The histological structure in no 
 
 way contradicts such a supposition, for, as we have 
 
 already seen (Fig. 391), the larval body in all essential points 
 
DISTRIBUTION AND MEDICINAL SIGNIFICANCE. 729 
 
 resembles that of the adult form. It can at the most be said that its 
 musculature is inferior in development and strength. But this is 
 only true when the developed joints are included in the comparison, 
 for the neck of the Bothriacephalua and, as may be readily conceived, 
 only this ought to be compared with the larval body presents hardly 
 any characteristics beyond those exhibited by the bladder-worm from 
 the pike. Even the musculature of the head of the larva, when 
 protruded, exhibits exactly the same relations as subsequently, and 
 consists of direct prolongations of the longitudinal fibres of the body. 
 
 Distribution and Medicinal Significance. 
 
 While the large-jointed Tcenice of man, and especially T. saginata, 
 may almost be regarded as cosmopolitan parasites, the distribution of 
 Bothriocephalus latus is much narrower, and its occurrence more 
 restricted. It has hitherto been observed with certainty in but few 
 places outside Europe. According to Yerrill, it is found, though but 
 rarely, in North America, and, according to Baelz and Ijima, it is 
 frequent in Japan. In Europe, moreover, it only occurs in certain 
 countries and districts. The most noteworthy localities are the coasts 
 of the Baltic, especially the more easterly, and Switzerland, particu- 
 larly the west. As is well known, the latter country furnished the 
 first instance of Bothriocephalus. According to Zaeslein, 1 to whom 
 we owe very thorough information regarding the occurrence of Bothrio- 
 cephalus in Switzerland, the worm was formerly principally confined 
 to the shores of the Lakes of Biel, Murten, Neuenburg, and Geneva. 
 These localities may still be described as the principal seats of the 
 parasite, although in some places for example, in Geneva, where, 
 according to Odier, a fourth of the population suffered from it it has 
 in the course of time become much less frequent. On the other hand^ 
 there are still places on the shores of these lakes (for example, Nidau, 
 on the Lake of Biel) in which one adult out of every five suffers from 
 this tape-worm. Children under ten are usually exempt. Some 
 leagues (not more than four) from the water, Bothriocephalus is found 
 much less frequently, especially among an agricultural population. 
 The same is true in a greater degree of the more distant parts of the 
 surrounding country, for there the worm appears only in the towns, 
 usually in consequence of transference, and is only in a few places 
 (Burgdorf and Thun) autochthonic. In the rest of Switzerland Bothrio- 
 cephalus only occurs sporadically, although there may be no want of 
 lakes abundant in fish. Huss 2 reports that among the sea-coast popu- 
 
 1 CorrespondenzUatt fur schiveizcr Aerzte, Jahrg. xi., p. 673, 1881. 
 
 2 " Ueber die endemischen Krankheiten SchwedeDS : " Bremen, 1854. 
 
730 DISTRIBUTION AND MEDICINAL SIGNIFICANCE. 
 
 lation of the Swedish province of Nordbotten no one, whether rich or 
 poor, old or young, is exempt, not even unweaned children. Further 
 inland in this case also the worm becomes gradually less frequent, and 
 at the distance of some miles hardly an instance is found. We are 
 also informed by Schauinsland that on the Kurische Nehrung hardly 
 one of the fisher-folk is free from the worm. In St. Petersburg the 
 number of the Bothriocephalus patients is estimated at 15 per cent., 
 and at Dorpat Szydlowski 1 found the eggs of the parasite in 10 per 
 cent, of the faeces examined. 
 
 It seems that the worm is also very widely distributed in the 
 interior of Eussia. We know of its occurrence in Poland, as well as 
 in the southern provinces, where Pallas had already observed it, 
 The dwellers on the shore of a lake near Kasan are said to be 
 afflicted by it with special severity (Knoch). In Moscow, on the 
 other hand, the parasite occurs but rarely. Of 200 tape-worm 
 patients chronicled by Krabbe, 2 noted in Denmark, twenty were 
 infected with Bothriocephalus. Most of them came from Zealand, in 
 which island, and especially in Soro, the worm is anything but rare. 
 In France and Italy 3 Bothriocephalus is found principally in the 
 regions near Switzerland. It was observed in Holland by van 
 Doeveren, and in Belgium by Spiegel, but apparently * has not since 
 been noted in either of these countries. The occurrence of Bothrio- 
 cephalus in Germany is mainly limited to the coast regions of eastern 
 Prussia and Pomerania, but some cases, which are to all appearance 
 autochthonic, have been noted in Hamburg, Berlin, Mainz, and 
 Munich. A very interesting communication on this subject is 
 made by Bellinger, 5 according to whom Bothriocephalus lotus has, 
 during the last four or five years, been observed no fewer than eight 
 times in Munich (among twenty-seven cases of tape-worm), and 
 exclusively in persons who, for some time before the appearance of 
 the parasite, had not left Munich, and who, in the majority of 
 instances (in five), were known to have resided on the banks of Lake 
 Starenberg. As no similar cases were observed at an earlier period, 
 
 1 "Beitrage zur Mikroskopie der Faeces," Inaugural-Dissert., Dorpat, 1879, p. 51. 
 
 a "Om Forkomsten af Bandelonne hos Mennesket i Damnark," Nord. med. Archiv, 
 Bd. xii., No. 23, 1880. 
 
 a Of fifty-seven cases of tape-worm which E. Parona observed in Varese, thirteen 
 were due to Bothriocephalus, twelve to Tcenia solium, and twenty-six to T. saginata 
 (Giornale Reed Accad. di med. di Torino, Marzo 1882). Regarding the occurrence of 
 Bothriocephalus in the north of Italy, see also Perroncito, " Parassiti dell'uomo et degli 
 animali utili," 1882, p. 250. 
 
 * My esteemed friend Ed. van Beneden has just written to me of a young girl in 
 Verviers who voided a Bothriocephalus, although (with the exception of a day spent in 
 Aix-la-Chapelle) she had never left the place of her birth. 
 
 6 Deutsches Archiv f. klin. Med., Bd. xxxvi., p. 277, 1885. 
 
SOURCES AND MODES OF INFECTION. 731 
 
 it seems very probable that in consequence of the increased commerce 
 on the shores of Lake Starenberg, the fish from which is carried as 
 far as Munich, there has arisen during the last decade a new centre 
 of infection of Bothriocephalus. It is likely that the infection was 
 carried to this district, which has recently been much visited, either 
 from Eussia or Switzerland, and that now it is itself a breeding- 
 place of the parasite. 1 It is uncertain whether the sporadic cases 
 which have been noted in London, St. Malo, Montpellier, Eome, and 
 other places on the Continent, are imported or autochthonic. 
 
 According to the experiments of Braun, to which we have already 
 referred, it can no longer be doubted that the BotJiriocephalus is intro- 
 duced into man by eating fish, and particularly pike. It is true that 
 the danger of infection is not everywhere equally great. As may be 
 readily understood, its degree is determined by the occurrence and 
 frequency, not only of the fish, but of the host, which in its turn 
 infects the fish. The infection may also be furthered in a very high 
 degree by certain local arrangements, and particularly by those which 
 afford to the faecal masses an unhindered and speedy entrance into 
 the water, so that, as we have already seen, regular breeding-places of 
 the parasite arise, from which, in proportion to the means of com- 
 munication, it will be carried further and further by the intermediate 
 hosts. If the fish be properly prepared and sufficiently boiled or 
 fried, it may, of course, be eaten without injurious consequences, even 
 if it contain larvse of Bothriocephalus. But it is otherwise if the 
 culinary process be not sufficient to kill the latter. Smoked pike, 
 which in some places e.g., in Dorpat and its surroundings forms 
 a common article of food, is according to Braun especially dangerous, 
 being often so carelessly prepared that he has several times found in 
 the fish living larvae. The degree of temperature required to kill 
 them has not been thermometrically determined, but the fact that the 
 worms remain alive even in hard frozen pike suggests a great 
 power of resistance. We have already seen that only the pike and 
 burbot have been proved to transfer the Bothriocephalus. This, how- 
 ever, by no means excludes the possibility that other species, perhaps 
 even some of the most favourite edible fish, may yet be proved 
 equally dangerous (see p. 717). 
 
 The oftener such fish are eaten, the greater is the danger of infec- 
 tion, and especially if little care be expended in cooking. Thus we 
 find, for example, in Dorpat, that the poorer classes, who live mainly 
 on the previously mentioned smoked pike, are the chief sufferers from 
 
 1 Huber has recently reported an instance of the occurrence of Hothriocephalus in a 
 coachman who had never left Swabia and Lower Bavaria (Acrztliches Intelligenzblatt, No. 
 8, 1885). 
 
732 DISTRIBUTION AND MEDICINAL SIGNIFICANCE. 
 
 Bothriocephalus, and that, as Schauinsland has reported, not one of the 
 fisher-folk in the Kurische Nehrung is exempt. In such cases it is 
 also not at all uncommon for several members of the same family to 
 be infected with the worm at the same time, or for several specimens 
 to live together in the same intestine, as is, for example, expressly 
 stated by Huss to be the case among the coast population of Nord- 
 botten. We have already seen (p. 720) that the students to whom 
 Braun administered several larvaB of Bothriocephalus produced almost 
 the same relative number of young worms ; and C. Vogt relates of him- 
 self that, after having lived eighteen months in the neighbourhood of 
 Geneva, he once voided 1 eight of these worms at one time. Mention 
 has already been made of Bb'tticher's case (p. 715), in which over a 
 hundred young Bothriocephali were found. We may also consider it 
 due to the mode of life that children, on the whole, but rarely suffer 
 from Bothriocephalus, and that women, who are busied in the kitchen, 
 are more liable than mer. Of the eight tape- worm patients observed 
 by Bellinger in Munich, only three were males, and among his twenty 
 cases Krabbe only mentions one. In Varese, on the other hand, 
 Parona found among thirteen patients only five women. 
 
 Our increased knowledge of the habits of intestinal worms has 
 dissipated an idea which has been several times expressed, namely, 
 that Bothriocephalus and Tcenia mutually exclude each other. Cases 
 of such a simultaneous parasitism are not wanting in recent literature, 
 although the necessary conditions do not perhaps frequently occur. 
 
 It has, however, been proved by the above-mentioned feeding 
 experiments of Braun that man is not the only host of Bothriocephalus 
 latus. The occurrence of the worm in the dog has already been noted 
 by Linne* and Pallas, and more recent investigations in very various 
 localities have confirmed these statements (von Siebold, Krabbe, Per- 
 roncito, and Braun). Whether the cat is infected spontaneously is 
 less certain. It is true that Creplin found some specimens of Bothrio- 
 cephalus in a domestic cat in Greifswald, but they were too young to 
 be certainly determined. 2 So, too, the Bothriocephali which Krabbe 
 observed in Copenhagen in a cat, and which he describes as 15 to 20 
 cm. in length, with large lancet-shaped head, and numerous calcareous 
 corpuscles in the joints, are certainly different from B. latus. 3 Further, 
 the Bothriocephali of the dog are by no means all of the same kind ; 
 for in Iceland alone Krabbe noted no fewer than three different 
 species, 4 and probably the B. cordatus of Greenland ought to be re- 
 garded as a fourth. 
 
 1 " Die Herkunft der Eingeweidewiirmer des Menschen," p. 16, 1878. 
 
 a " Observationes de Entozois :" Gryphiswaldiae, 1825, p. 67. 
 
 3 " Recherches helminthologiques en Denmark et en Islande: " Copenhagen, 1860, p 19. 
 
 * Ibid., p. 27. 
 
SPECIFIC AND INDIVIDUAL DIFFERENCES. 733 
 
 We must, however, remember that the specimens of Bothriocephalus 
 latus occurring in the dog and cat not only develop much more slowly 
 than in man, but differ more or less strikingly in size. It is true that 
 the worms in man have not always the same appearance. This is 
 sufficiently evident from the fact that, besides the real and typical 
 Bothriocephalus latus, or in place of the latter, both the earlier and 
 more recent Helminthologists have thought themselves justified in 
 distinguishing several different species. Thus Linne* spoke of Tcenia 
 vulgaris and of T. lata ; Pallas of T. grisea, T. lata, and T. tenella ; 
 Goze of T. memlranacea and T. lata all of which, although regarded 
 as Tcenice, belong to Bothriocephalus latus. 
 
 These species were distinguished, not only on account of the false 
 ideas which then prevailed regarding the structure of the head in 
 Tcenia lata, but especially on account of the different physiognomy of 
 the worms, and the structure of their joints and uteri. Although 
 Grassi * has lately tried to identify with Linnets Tcenia lata the Both- 
 riocephalus cordatus discovered by me, which we shall afterwards more 
 specially consider, I must continue to regard it as a distinct species. 
 On the other hand, I think that, notwithstanding its inconsiderable 
 length (1-8 metre), and the smallness of its joints, the form described 
 by the latter (without name), and also the Bothriocephalus cristatus of 
 Davaine, ought to be regarded as belonging to B. latus. 
 
 The differences which can be observed in the worm are to be re- 
 ferred partly to an unequal state of contraction, and partly and more 
 especially to differences in age, growth, and food. As Botticher has 
 already noted, there are " well-fed " worms, and others which are 
 extremely emaciated and appear as thin as paper. The former are 
 more or less coloured, yellowish or yellowish-brown, according to the 
 distention of the yolk-glands, while the latter are colourless, and have 
 but slightly developed sexual organs with few eggs. In the same 
 way there are large and small Bothriocephali ; some, with a size of 2 
 metres or even less, attain their full development, as is evident from 
 the fact that in them the greatest breadth and greatest distention of 
 the uterus do not coincide with the end of the chain, but usually 
 occur some distance anterior to this, at least if a number of proglottides 
 have not previously been cast off. Moreover, such examples are not only 
 shorter than the average, but their joints are smaller, having a length 
 of 2 to 2'5 mm., and a breadth of perhaps 5 to 6 mm., while usually 
 the latter is double this, or even more (as much as 20 mm.). Thus it 
 happens that the relations of length and breadth in the joints often vary 
 throughout considerable portions, or even throughout the whole of the 
 body ; and under some circumstances the length of the joints becomes 
 
 1 " Intorno ad un Bothriocephalus dell' uomo," Ann. univ. di Meet., vol. cell., p. 8. 
 
734 DISTRIBUTION AND MEDICINAL SIGNIFICANCE. 
 
 even greater than the breadth, so that this feature, formerly so charac- 
 teristic of Bothriocephalus, disappears more or less completely. And 
 this is all the more apt to take place from the fact that in such cases 
 the uterus is usually considerably distended, and exhibits loops far 
 separated from one another ; so that, in place of the usual rosette-like 
 form, a structure arises which is at first sight almost Tsenioid in 
 character. But in spite of their different appearance, these worms do 
 not really differ from the typical Bothriocephalus. One has only, as 
 Botticher has shown, to treat them with warm water in order to see 
 the joints greatly shorten, with simultaneous increase in breadth, until 
 they finally assume the usual form of Bothriocephalus latus. 
 
 Not only the joints, however, but also the neck and head, assume, 
 according to circumstances, a different form. The former is at one 
 A B time slender and stretched out, so that the segmentation 
 
 only begins at a distance of 15-25 mm. behind the 
 head, where the breadth amounts to perhaps 0'25 mm. 
 (Fig. 357), and at another time (Fig. 358) very broad and 
 thick (1*5-2 mm.), and so short that the segmentation 
 can be traced almost up to the head. The appearance 
 of the latter is just as variable. During life, and even 
 under the eye of the observer, it often changes its oval 
 form (Fig. 358) for one more like a club. Further, the 
 _ anterior end appears at one time flattened out, at an- 
 Ciub-shaped head other more pointed ; the border of the suctorial grooves 
 
 j s sometimes straight and sometimes undulating, while 
 
 latus. A, Seen D . ' 
 
 from the edge ; the grooves themselves may be either narrow and con- 
 B, From the flat tracted or wide open. All these states may be occa- 
 
 surface. (x8.) . ,, , . . 
 
 sionally observed in preserved specimens. 
 
 In our description we have already shown to what considerable 
 size Bothriocephalus may grow. Nor is even the length there men- 
 tioned the maximum which the worm may attain. Pallas mentions 
 a specimen 56 feet long, and from other quarters also we have heard 
 of unusually long specimens. If we consider that the worm does not, 
 like the large-jointed Tcenice, throw off the proglottides singly, but in 
 portions several feet in length, and at irregular and often long inter- 
 vals, and if, on the basis of the vegetative conditions established by 
 Braun (8*8 cm. per day), we estimate the yearly growth approximately 
 at 100 feet, it will be seen that the existence of such gigantic worms 
 is by no means an impossibility. 
 
 This estimate of the growth almost entirely agrees with the state- 
 ment of Eschricht regarding a patient suffering from Bothriocephalus, 
 who within a year voided 70 feet of tape- worm, 20 of which, it is true, 
 belonged to the parasite itself, which finally found an exit along with 
 
DESCRIPTION OF BOTHRIOCEPHALUS CKISTATUS. 735 
 
 its head. The amount cast off in the year, in pieces usually 2 to 4 feet 
 long, may accordingly be estimated at about 60 feet. If the worm 
 were expelled almost as far as the head, six to eight weeks would 
 sometimes suffice to allow it to grow to 6 to 8 yards. At all events, 
 the growth of Boihriowphalus is much quicker and more energetic than 
 in the case of the large-jointed Tcenice of man. 
 
 It is probably, too, on account of the unusual length of the worm 
 and the great flexibility of its body, that it is by no means so easy to 
 expel as one would imagine from the weak development of the attach- 
 ing apparatus. 
 
 It is hardly possible to state with certainty how long the parasite 
 may remain in man. It is probably not behind the large-jointed 
 Teenies in this respect. At all events its existence may extend over 
 many years. Bremser mentions the case of a native of Switzerland, 
 who had lived for twelve years out of his native country, but had 
 observed the presence of the worm only a year before, and as the 
 stretches of joints contained in the faeces may easily escape notice, it 
 is by no means impossible that the parasitism had extended over an 
 even longer period. Hosier also reports two cases of BotJiriocephalus, 
 one of which was six years old, and the other probably fourteen, but 
 certainly ten. 1 Since the ova, as we have seen, are allowed to escape 
 in such great numbers that the uteri in the last joints, if these have 
 remained for some time in connection with the rest of the chain, are 
 usually quite empty, the examination of the faeces demonstrates the 
 presence of the parasite with absolute certainty, even when it has 
 been otherwise unobserved by the host. As a rule, however, the 
 parasite soon makes its presence felt according to Braun's experi- 
 ment, three weeks after inspection by occasioning difficulties in 
 digestion, like those caused by the larger Tcenice. These effects (gripes, 
 loss of appetite, sickness, &c.) apparently follow the presence of 
 Bothriocephalus with more certainty and intensity than that of Tcenice, 
 sometimes, or even frequently, producing nervous disorders, especially 
 in women. Prolonged persistence occasionally produces marked ema- 
 ciation, while other cases occur in which the worm does not cause the 
 slightest inconvenience. The possibility of self-infection is seen, of 
 course, to be excluded by the life-history of the parasite. 
 
 P Bothriocephalus cristatus, Davaine. 
 
 Davaine, "Traite des Entozoaires," second edition, supplement, p. 928 : Paris, 1877. 
 
 Some years ago Davaine described under the above title a form of 
 Bothrioceplialus which he regards as representative of a distinct species, 
 
 1 Virchow's Archivf, path. Anat., Bd. Ivii. 
 
736 DESCRIPTION OF BOTHRIOCEPHALUS CORDATUS. 
 
 though its peculiarities do not appear to me sufficient to justify his 
 opinion. His description was based on two specimens one without 
 a head, which was found in a man forty years old, from the Depart- 
 ment of Haute Saone, while the other with the head was obtained from 
 a child five years old in Paris. * The former measured 92 cm. in length, 
 but was apparently much contracted, as might be inferred, not only from 
 the segmentation, which extended close up to the head, but also from 
 the form of the proglottides, which possessed considerable thickness, 
 but were never more than 1'5 mm. in length, and had their posterior 
 borders much protruded, so as to embrace in an almost cuff-like fashion 
 the succeeding joints. At a distance of about 20 cm. from the head, 
 the breadth of the chain increases abruptly from about 1 to 4 mm., and 
 then gradually to 9 mm. The head, which suggested the name " crista- 
 tus," is said to be especially characteristic of this form. It is of con- 
 siderable size (3 mm. long, 1 mm. broad, 0*6 mm. thick), and in shape 
 resembles a grain of linseed with the point turned forwards. There are 
 no proper suctorial grooves, but according to the description, the two 
 surfaces of the head are each provided with a projecting ridge, which 
 extends from the anterior apex, and is divided by a furrow into two 
 longitudinal lips. These lips diverge posteriorly, and enclose a groove 
 resembling the calamus scriptorius in the brain. The margins of the 
 ridges are covered with small papillae, and the rest of the head is 
 marked by transverse wrinkles. Characteristic of this form are the 
 numerous calcareous bodies, which penetrate the parenchyma of the 
 head in four longitudinal strands, and extend in such abundance 
 through the neck into the body that Davaine refers, its thickness and 
 stiffness to these deposits. The total length is said not to be more 
 than 3 metres. The ova resemble those of Bothriocephalus latus. 
 
 Bothriocephalus cordatus, Leuckart. 
 
 Leuckart, " Die menschlichen Parasiten," first edition, Bd. i., p. 437 et teq., 1863. 
 
 In the structure of its joints, this form is not unlike Bothriocephalus 
 latus, but on closer inspection cannot be confused with it, not only because 
 of its considerably smaller size and more compressed form, but especially 071 
 account of the structure of the head and anterior end of the body. Un- 
 like the extended, oval, or club-shaped head of Bothriocephalus latus, the 
 head of this form is short, broad, and cordiform, with lateral borders, which 
 
 1 Davaine supposes, it is true, that his B. cristatus is of much more frequent occur- 
 rence. He refers to a report of Cobbold, according to which several worms preserved in 
 the Westminster Hospital Medical School belong to his species, and also to an anonymous 
 Memoir published in 1776 in Kempten, in which his worm is said to be figured in a 
 thoroughly satisfactory fashion. 
 
DEFINITION OF BOTHKIOCEPHALUS CORDATUS. 
 
 737 
 
 usually project from the surface, and are drawn out longitudinally on 
 either side, into a deep and sharply defined suctorial groove. Behind 
 this head extends, not a long, narrow, neck-like anterior portion, but 
 the broad body with its segments, which are from the first readily 
 recognisable by the naked eye, and which increase in size so quickly that 
 the worm acquires anteriorly a lancet-like form. At a distance of 3 cm. 
 behind the head, the joints are already sexually mature, and 3 cm. 
 farther back they have attained almost their maximum breadth (7 to 8 
 mm.). The number of immature joints is at the most about 50, and the 
 great majority of these exhibit distinct genital apertures. Their imma- 
 turity consists only in the absence of hard-shelled ova. There is no dis- 
 tinction between median and lateral regions in the immature joints. 
 These only become distinguishable with increasing maturity, when the 
 median have a clear appearance, while the lateral portions are a dark 
 grey colour, which gradually becomes more and more marked. The 
 length of the mature joints is on an average between 3 and 4 mm., but 
 the contractility of the worm is so great that they sometimes measure only 
 1*3 mm., with a corresponding increase in breadth and thickness. Only 
 the terminal joints are exceptional, in having generally a square form, 
 
 FIG. 395. 
 
 FIG. 394. 
 
 A 
 
 FIG. 396. 
 
 FIG. 394. Head and anterior portion of Bothriocephalus cordatus, seen (A) from the 
 side, and (B) from the surface. ( x 5.) 
 
 FIG. 395. A number of mature joints of B. cordatus (nat. size). 
 FIG. 396. Uterus of B. cordatus (nat. size). 
 
 measuring each way 5 to 6 mm. In the largest worms, 115 cm. long 
 (with a head 2 mm. long and broad), there are about 600 joints, but the 
 
 3 A 
 
738 DESCRIPTION OF BOTHRIOCEPHALUS CORDATUS. 
 
 number is as a rule less, and usually only 400. The middle of the 
 dorsal surface is traversed by a longitudinal furrow. A similar longi- 
 tudinal furrow is recognisable on the ventral surface below the genital 
 apertures. Especially characteristic and distinctive are the form of the 
 head, the great number of calcareous corpuscles embedded in the paren- 
 chyma of the body, and the structure of the uterus, which is not only 
 narrower and longer, but exhibits a larger number (6 to 8) of lateral horns. 
 
 This worm occurs in the north of Greenland (Godhavn), but has 
 only been found once as yet in man. It is, however, frequent and 
 abundant in the dog, and occurs also, according to Krabbe, 1 in the 
 seal (Phoca barbata) and the walrus. 
 
 I owe my opportunity of investigating this new species to the 
 kindness of my renowned friend Professor Steenstrup, who obtained 
 the worm, along with a large number of other Helminths, from Dr. 
 Olrik, the Danish Government Inspector of Northern Greenland. I 
 was able to compare about twenty specimens, young and old, of which, 
 however, only one was, as above mentioned, derived from the human 
 subject. The latter was accompanied by a history of the patient, 
 which, as translated from Professor Steenstrup, runs as follows : " The 
 worm was obtained from a half-breed, Koren Margrethe, married to a 
 half-breed, Peter Broberg, in Godhavn (North Greenland, 70 N. lat.). 
 The patient is thirty-four years of age, was married in her tenth year, 
 and has four children. She expects in September next (1860) her 
 fifth accouchment. Since the beginning of pregnancy, she has suffered 
 from severe stomachic pains, associated with violent vomiting, and has 
 been otherwise unwell, although in her former pregnancies she had 
 not the slightest symptom of this kind. She was not able to eat any- 
 thing young, neither young bird nor young seal. In the vomit there 
 was no trace of tape- worm, but on the 30th June she voided with the 
 faeces a long, broad tape-worm, which was unfortunately not pre- 
 served. Some days later vomiting again set in, and shortly afterwards 
 (8th July) she voided a tape-worm (Fig. 397). This was smaller 
 than the former, though it measured, when living, fully a finger-breadth 
 in diameter. The patient had never before remarked anything of the 
 kind, and had not even suffered from the Ascarides (Oxyuris), so 
 common among Greenlanders. After voiding the worm, the patient 
 (who it may be mentioned was the sister of my maid-servant) felt 
 somewhat relieved. As the stomachic pains, however, did not cease, 
 she presumed the presence of other worms. The vomiting, however, 
 was alleviated. With the stomachic pains a watery diarrhoea was 
 always associated, in the course of which both worms escaped. Before 
 
 1 " Rech. helminthol.," p. 33 : Copenhagen, 1866. 
 
OCCURRENCE IN MAN. 
 
 739 
 
 I left Greenland the excrement had become firmer, but the patient 
 was still very thin, which was contrary to her usual tendency." 
 
 Whether the above history describes the symptoms of a helmin- 
 thiasis, or the attendant effects of pregnancy, can, in spite of the 
 
 FIG. 399. Three 
 joints, seen (A) from 
 dorsal, and (B) from 
 the ventral surface, 
 (x 2.) 
 
 FIG. 398. Head of the 
 same (A) from the side, (B) 
 from above. ( x 8.) 
 
 Fio. 397. Bothriocephcdus 
 co?*causfromman (nat. size). 
 
 antecedents, hardly be determined; the account serves, however, as 
 documentary evidence of the occurrence of the worm, and is therefore 
 included in the present account. 
 
 At first sight the worm appeared not a little different from the 
 tape-worms of the dog which were sent along with it, though the 
 
740 DESCRIPTION OF BOTHRIOCEPHALUS CORDATUS. 
 
 difference did not amount to the absence of any important character. 
 The structure of the head and of the anterior part of the body, the 
 disposition of the uterus, the abundance of calcareous corpuscles, left 
 no doubt at all as to its identity ; but the general habit was very 
 different, so that a specific distinction was almost suggested. The 
 total length was only about 26 cm., though the number of joints 
 amounted to fully 300. The anterior hundred occupied about 30 
 mm., the middle hundred 100 mm., and the posterior hundred 130 mm. 
 With a breadth of 6 mm., the individual joints were never more than 
 1'3 mm. long, and in a portion near the middle of the worm not more 
 than 0'8 mm. Twenty millimetres behind the head, which measured 
 about 1*5 mm. in both directions, the body had almost attained its 
 full breadth (5 mm.). 
 
 The worm was characterised not only by the shortness of the 
 joints, but by their thickness, which measured between 3 and 4 mm., 
 showing beyond doubt that it was in a very contracted state. This 
 resulted probably from the fact that the worm, immediately after 
 being voided, and still in possession of its full muscular power, was 
 thrown into strong alcohol. There were among the tape-worms from 
 the dog other specimens, which were, in part or altogether, as strongly, 
 or even more strongly, contracted. This was especially well seen in 
 a worm, which, in spite of its 460 joints, measured only 164 mm. in 
 length, and bore posteriorly proglottides only 1/3 mm. long. The 
 breadth (7'5) was greater, of course, than in the above specimen, but 
 the thickness, especially of the lateral regions, was much less. 
 
 Under the circumstances, I have not the slightest doubt that all 
 these worms belong to the same species, and hence it seems to me 
 certain not only that the Greenland dog harbours a species of Bothrio- 
 cephalus different from B. latus, but also that this form occasionally 
 occurs in man. 
 
 Further observations are indeed required as to the frequency of its 
 occurrence in man. In the Greenland dog the species must be one of 
 the commonest intestinal parasites, for all the specimens (about twenty) 
 which I examined were obtained within half a year, and, with the 
 exception of one, in three months ; and that, too, at one place, Godhavn, 
 the seat of the Danish Government inspector. The worms were 
 derived from five dogs, of which two produced one each, a third two, a 
 fourth eight, and the fifth all the others. These last were taken from 
 the intestine of the dog after death, one of them still firmly attached 
 to one of the villi ; the others, some of which had lost the head, were 
 spontaneously expelled from their hosts. 
 
 Whether this species occurs in other localities is still unknown. 
 The report of its discovery in Dorpat has proved to be erroneous. 
 
ITS SPECIFIC DISTINCTNESS. 741 
 
 Grassi thought, indeed, that Linne's Tcenia lata might be referred 1 
 to our Bothriocephalus cordatus, but from the description and figures 3 
 it seems to me as though it differed only in its greater contraction 
 from the more elongated T. vulgar is, and thus simply represented a 
 much contracted specimen of T. lata. Of T. lata it is indeed said 
 " rarissime in hominibus vermis observatur, vulgatissimus auteni in 
 canibus ; " while in regard to T. vulgaris nothing is said of its occur- 
 rence in the dog, but merely, " vulgatissimus (vermis) inter Tsenias 
 homines infestantes ; " but this alone is not enough, and the differ- 
 ences between the species as noted by Linne may perhaps be due 
 to the worms from the dog having been examined in a lively and 
 contractile state, while those from man were observed only when 
 exhausted or even dead. The descriptions indeed suggest this 
 supposition. 3 This much, at any rate, is certain, that the description 
 of T. lata affords no decisive proof of its identity with our B. cordatus. 
 The head, which ought to form the primary object of investigation, 
 is not described either in T. lata or T. vulgaris, and was perhaps not 
 even seen. 
 
 Be that as it may, a denial of the specific distinctiveness of B. 
 cordatus seems to me henceforth impossible. Even the separated 
 joints can be readily distinguished from those of B. latus, less perhaps 
 on account of their form, though that, too, is diagnostic, than on account 
 of the calcareous corpuscles, which are as abundant in the Greenland 
 species as they are rare in the Swiss or Eussian tape- worm. They 
 are thickly distributed through all the layers of the body, and some- 
 times attain a size of 0*028 to 0*03 mm. The peculiarity in the 
 structure of the uterus has been already noted. Similarly the 
 stronger development of the muscles, especially of the longitudinal 
 muscles in the cortical layer, must be noted as characteristic of B. 
 cordatus, and this explains the striking contractility of the worm, as 
 also the large size of the cirrhus-pouch (0'6 mm. long by 0'43 mm. 
 broad), as compared with that of B. latus. These are, however, points 
 of detail, and, for diagnostic purposes, unimportant in comparison 
 with the structure of the head and anterior portion of the body. 
 
 In the larger worms the head has a length of 2 mm., and a pro- 
 portionately large breadth. Viewed from the flat side, the anterior 
 half appears pointed, while the lateral portions project posteriorly, 
 more or less like wings, according to the degree of contraction 
 
 1 Ann. univ. di Med., vol. ccli., 1880. 
 
 2 " Amoenit. Acad.," vol. ii., p. 71, Fig. 3. 
 
 3 Thus it is said of T. lata, " Dum adhuc vivus est et se extendit, uno alterove loco 
 filifonnis evadit, et articuli iis in locis graciles fiunt, atque post ejus mortem lati sunt," 
 while no mention at all is made of the living state of T. vulgaris. 
 
742 
 
 DESCRIPTION OF BOTHRIOCEPHALUS CORDATU8. 
 
 exhibited by the head (Fig. 394). The shape of the head of course 
 varies, but may be generally compared to the heart in a pack of 
 cards, or to an arrow-head. The flattening increases gradually 
 towards the point, but is, on the whole, not conspicuous, and least so 
 in the posterior half, where the rudiment of the subsequent lateral 
 margins of the body is recognisable. 
 
 The anterior half is distinguished, not only by its flattening, but 
 also by the depth of its marginal grooves, which is so considerable, 
 
 that they are separated from one 
 another only by a thin partition. On 
 the other side of the middle of the 
 head, the depth and width of the 
 grooves gradually decreases, until a 
 shallow furrow alone remains. With 
 the depth of the grooves the more or 
 less free development of the limiting 
 lips is associated. That the latter, 
 even where most independent, are 
 without any proper musculature, has 
 been already mentioned as character- 
 istic of the genus Bothriocephalus. 
 The fact is readily demonstrated in 
 transverse sections, in which one can 
 also convince one's self of the general structural and histological 
 resemblance between the head and the rest of the body. In the 
 head, as elsewhere, a median layer and a peripheral muscular sheath 
 are distinguishable, both but slightly diverging from the ordinary 
 type. The internal wall of the marginal grooves is, of course, formed 
 from the cortical layer, which is here so thick that the middle layer 
 in the anterior half of the head is entirely displaced by the layer 
 connecting the two lateral surfaces. In the middle layer, besides 
 numerous calcareous corpuscles, the two nerve strands can be 
 recognised, disposed opposite to one another in the direction of the 
 smaller diameter. 
 
 The structure of the generative organs does not differ typically 
 from that of B. latus ; and I have not been able to elucidate their 
 development. The ova closely resemble those of the Swiss tape-worm, 
 but are on an average somewhat larger (O075 to 0*08 mm. long, by 
 0'05 mm. broad). 
 
 It was to be expected from the analogy with B. latm, that B. 
 cordatus would liberate its joints in groups, and not singly. The 
 specimen (Fig. 397) obtained from the patient, as above described, 
 most clearly suggested the occurrence of this process. At a distance 
 
 FIG. 400. Transverse sections of 
 the head of Bothriocephalus cordatus ; 
 A, before, B, behind the middle. ( x 
 about 20.) 
 
PECULIARITIES OF YOUNG SPECIMENS. 
 
 743 
 
 of 23 mm. from the posterior end of the body, an annular constriction 
 was evident, 1*5 mm. deep at one lateral margin, and 1 mm. at the 
 other, and separating off the last seventeen joints. A second con- 
 striction occurred 17 mm. further up, isolating an almost equal 
 number of joints (fifteen), but less deep than the one behind. 
 
 I do not think I am wrong in regarding these grooves as the first 
 signs of the commencing separation, and am confirmed in this opinion 
 by the fact that they do not coincide with the boundaries of two 
 joints, but extend across the surface of a joint. Since the end of the 
 chain exhibited only half a joint with a cirrhus-pouch, my supposi- 
 tion seems fully justified. 
 
 Among the specimens of Bothriocephalus cordatus, there were, 
 besides adult chains of joints, several young 
 worms, which were of special interest on 
 account of several peculiarities, which have 
 not, so far as I know, been elsewhere observed 
 in young Bothriocephali. It was even possible 
 to form a tolerably complete series of such 
 forms, and thus to elucidate in an unex- 
 pected manner the early stages of the species. 
 
 The smallest of these young worms 
 measured not more than 30 mm. It ex- 
 hibited, like the others, a clear, almost 
 transparent appearance, due not only to the 
 absence of cortical granules, but especially 
 to the thinness of the body and the 
 slight development of the muscles. The 
 greatest breadth (3 mm.) was exhibited a 
 short distance behind the head. The anterior 
 end already showed the characteristics noted 
 in the adult. The posterior third of the 
 body was, however, strikingly different, be- 
 coming gradually narrower, and ending in a 
 thin point. The head exhibited the adult 
 form, but was of much smaller size (0'8 mm.), 
 while the body was divided into about 140 
 narrow segments, of which those about the 
 middle were not only the broadest, but also 
 the longest. 
 
 The other worms exhibited a 
 structure, and measured from 40 to 100 mm., increasing gradually in 
 breadth to 5 '5 mm. Not only did these larger specimens resemble 
 the smaller in form, but even in the number of segments, which 
 
 FIG. 401. Four young 
 specimens of Bothriocephalus 
 similar cordatus (nat. size). 
 
744 DESCRIPTION OF BOTHRIOCEPHALUS CORDATUS. 
 
 varied from 125 to 154. The only differences associated with the 
 growth of the joints and head (measuring over a millimetre) lay in the 
 beginning of sexual development. Even in those 80 mm. in length 
 I could recognise in the larger middle joints a generative aperture 
 and cirrhus-pouch, and in the .interior, in soaked specimens, the 
 rudiments of the ducts, while in specimens 100 mm. long the genera- 
 tive apparatus could be seen in greater completeness and distinctness. 
 The median region had at the same time swollen out into a longitudinal 
 elevation, as in adult forms, evidently an indication of further sexual 
 development. Curiously enough, it was the median segments of the 
 body which were best developed, not only in size (1'2 mm. long), 
 but in the structure of the generative organs ; only in larger forms 
 did this distinction disappear. In a specimen 27 cm. in length, 
 with 184 proglottides, which had already liberated some of its 
 posterior proglottides, all the joints except the anterior 40 to 60 
 were quite mature. 
 
 I thought at first that the above peculiarity was confined to this 
 species of Bothriocephalus. Since then, however, we have learned, 
 from the researches of Kahane 1 and Eiehm 2 , that in Tcenice also the 
 last joints of the chain are very often sterile and small, and that the 
 sexual development always begins at some distance from the oldest 
 joint. The number of these barren joints varies very considerably ; 
 though generally but few, they include in some species about half of 
 the whole chain, and thus give the young worms a form strikingly 
 different from that of the adults. In the case of Tccnia perfoliata 
 from the horse, the young form has, as Kahane has shown, been even 
 regarded as a distinct species (T. plicata). The case of B. cordatus is 
 probably similar ; the last joints of the young chain probably remain 
 sterile, and separate without further growth or development. B. latus 
 seems, according to Braun's report, to be different in this respect, so that 
 the present species probably exhibits also this difference in development, 
 though it can hardly be supposed that it stands alone in this respect. 
 In fact B. proboscideus from the salmon exhibits young forms with 
 6 to 16 joints, which when 1'9 to 4 mm. in length, exhibit the same 
 form and posterior structure as those of B. cordatus. The segmenta- 
 tion begins close behind the head, which has of course at first, as in 
 all Bothriocephali, a much smaller size than it subsequently acquires 
 with the development of its adult structure. 
 
 That it is from fish that the dog and man are infected with 
 Bothriocephalus cordatus, can, from the analogy of B. latus, hardly 
 
 1 Kahane, " Anatomic von Tsenia perfoliata." Zeitschr. /. Wins. Zod., Bd. xxxiv., 
 p. 184. 
 
 3 "Studien an Cestoden," p. 56 : Halle, 1881. 
 
DEFINITION OF BOTHRIOCEPHALUS LIGULOIDES. 745 
 
 admit of doubt, apart from the fact that it is these animals (along 
 with other aquatic animals, birds, and seals) that furnish a great part 
 of the food of the above-mentioned hosts. The infection can hardly 
 be difficult, since, according to travellers, the Esquimaux eat the flesh 
 either raw or but slightly cooked, and do not despise even the viscera. 
 No part indeed is put aside as uneatable ; neither care nor cleanliness 
 characterise their cooking, and the food is eaten with gusto when it 
 has been hardened by the frost. 
 
 BothriocephalTis liguloides, Leuckart. 
 
 Ligula Mansoni, Cobbold. 
 
 Cobbold, "Description of Ligula Mansoni, a new Human Cestode," Journ. Linn. Soc. 
 Lond. (Zool.), vol. xvii., p. 78, (with woodcut) 1883. 
 
 This worm, hitherto observed only in the larval form, exhibits in this 
 state a ribbon-like unsegmented body of a somewhat fleshy consistency. It 
 attains a length of 20 cm. and more, and has a median breadth of 2*5 
 mm. Posteriorly the worm becomes somewhat narrower, while anteriorly 
 it is for a short distance widened into a sort of disc. The anterior 
 margin, which is otherwise rounded, bears in the middle a papilli- 
 form elevation, on which the head proper is borne. The latter has a 
 somewhat compressed form, but is usually more or less completely 
 invaginated. No sexual organs are present, nor is there any perceptible 
 difference between the two surfaces of the body. The body is traversed 
 by irregular wrinkles, chiefly transverse, but partly also longitudinal, 
 which probably result from the state of preservation. 
 
 The normal habitat of the worm is the subperitoneal connective tissue 
 of man, especially, it seems, in the lumbar region. It has been hitherto 
 found only in China and Japan. 
 
 The first notice of the existence and occurrence of this peculiar 
 parasite is due to Dr. Manson of Amoy, whom we have recently had 
 to thank for a series of interesting observations on Filaria sanguinis. 
 No fewer than twelve specimens were found in the body of a China- 
 man, who died from dysentery and ulcerating stricture of the 
 oesophagus (after an operation for elephantiasis of the scrotum). 
 With the exception of a single worm, which lay free in the right 
 pleural cavity, the parasites were all found in the region of the fossa 
 iliaca behind the kidneys, embedded in the subperitoneal connective 
 tissue. 1 Some were coiled up, and others more or less extended. 
 They measured in the fresh state 30 to 35 cm., 2 were of a dead white 
 
 1 The history of the patient is given in the Lancet, 14th Oct. 1882. 
 
 2 Cobbold gives the length of the specimens preserved in spirits as 1*2 to 3 '3 inches. 
 
746 DESCRIPTION OF BOTHPJOCEPHALUS LIGULOIDES. 
 
 colour, and exhibited when removed from their resting-place distinct 
 tapeworm-like movements. 
 
 Before the publication of this notice, and 
 the accompanying communication of Cobbold, 
 to whom Manson sent his worms for closer 
 investigation, I also obtained a specimen of this 
 worm through the kindness of Dr. Scheube, 
 then director of the hospital in Kioto, now 
 physician in Gera. These were derived from 
 a Japanese, twenty-eight years of age, who 
 had been five years in prison, but was formerly 
 for some years a groom in the island of 
 Kiushiu, and had moved about in the west 
 of the main island. During his residence in 
 Kiushiu, he suffered after a prolonged careless 
 life from hsematuria. He became afterwards 
 syphilitic, and remained so till his imprison- 
 ment. After he had been five years in prison 
 his left testis began to swell and become 
 painful. At the same time a diffuse hardening 
 of the skin set in, on the upper part of the 
 left thigh, below the inguinal region, and 
 pains extended thence to the left hypochon- 
 driuin. Afterwards the hardening and the 
 pain decreased, and wholly disappeared for 
 some months, during which the patient, in 
 FIG. 402. Bothriocephalus S pite of the continuous slight enlargement 
 ' of the left testis, felt quite healthy. In the 
 course of a year, without apparent occasion, 
 dysuria set in, associated with pains in the urethra and bladder. The 
 urine itself exhibited no striking change. After the dysuria had lasted 
 for some days, the patient observed when making water the projection of 
 a white thread-like body, which moved when touched. He recognised 
 it as a worm, and attempted to extricate it by winding it round a 
 bamboo rod. After he had drawn out about 18'5 cm. in this fashion, 
 the worm broke. The pain of urinating was temporarily relieved, but 
 after a short period returned. The urine could only be expelled in 
 drops by strong pressure, and with violent pains, which extended to 
 the upper thigh. The urine was slightly cloudy, but on microscopic 
 examination, revealed nothing unusual except blood corpuscles. 
 Whether further portions of the worm were expelled is not known, 
 as the patient very soon returned from the hospital to the prison. 
 The worm, which in spirit had contracted to 13 cm., turned out 
 
ITS OCCURRENCE IN MAN. 747 
 
 to be an unusually long larva of a species of BothriocepJialus } identical 
 with the form which Cobbold had just ranked among the human 
 Entozoa, under the title Ligula Mansoni. From Manson's report, it 
 seems clear that its occurrence in the urethra in Scheube's case was 
 secondary. The worm does not live, as one might expect from the 
 above, in the renal cavities, but is primarily, like the other larvae of 
 BothriocepJialus } embedded in the connective tissue of the host, 
 probably, as in Manson's case, in the neighbourhood of the kidneys, 
 whence it had found its way, after further growth, into the urethra. 
 That it is able, to some extent at least, to change its position, is 
 evident from the fact that in Manson's case one specimen was found 
 in the pleura ; while Braun's observations on the bladder- worms from 
 the pike (p. 726) establish the occurrence of an occasional migration. 
 The loose nature of the enveloping sheath, and the ease with which 
 larvae of BothriocepJialus protrude their heads (as I observed on a 
 living form 6 cm. long, taken from the subdermal connective tissue of 
 a Japanese giant salamander), make the mechanical possibility of 
 this wandering readily intelligible. A passage into the ureter must 
 be less difficult for this form than for certain intestinal parasites, 
 which also occasionally make their exit in a similar manner. I refer 
 not only to the Ascarides, although they furnish the greater number 
 of such instances, but also to tape-worms which in larger or smaller 
 fragments have been evacuted with the urine (p. 486). 
 
 A new case of this kind has since been communicated to me by 
 Dr. Noll in Hanau. A patient was taken to the hospital there on 
 account of haemorrhage from the urethra, and some days later, 
 with comparatively slight pain, expelled with the urine some living 
 proglottides, which I identified as those of Tcenia saginata. None 
 were to be found in the stools. 
 
 It remains doubtful whether the abnormal symptoms exhibited by 
 the patient in Scheube's case before passing the worm were due to 
 the wandering of the parasite into the ureter, or were to be regarded 
 as the consequence of syphilis ; equally doubtful, too, was the time 
 and the manner of transmission. We cannot, however, be mistaken in 
 supposing that it was a case of straying on the part of the worm, and 
 that the latter was at first lodged, as in Manson's case, in the 
 peritoneum. 
 
 Cobbold considers the worm as a Ligula, even affirming that it is 
 nearer to L. simplicissima, which occurs so abundantly in our river 
 fishes, than to any other Cestode form, though he does not exactly go 
 the length of declaring it merely a variety of the former. I am sorry 
 to be forced to contradict my esteemed fellow- worker and friend. The 
 resemblance between this form and Ligula, especially L. simplicissima, 
 
748 DESCRIPTION OF BOTHRIOCEPHALUS LIGULOIDES. 
 
 is restricted to a mere similarity of external shape. The internal 
 structure is so different that a collation of the two seems almost im- 
 possible. Not only does L. simplicissima, though generally a larva 
 like the present form, contain already well-developed reproductive 
 organs, which attain full maturity a few days after their transference 
 to the final host, but the histological structure of the ribbon-like 
 body, and especially the disposition of the musculature, is thoroughly 
 different. 1 It has, besides, to be remembered that Ligula, i.e., the 
 true Ligula, whose representative is L. simplicissima, is in its inter- 
 mediate stage found exclusively in fishes. I speak designedly of the 
 true Ligula, for this name has been frequently bestowed by helmin- 
 thologists on the intermediate stages of Bothriocephalus, and especially 
 on those which are characterised by the possession of a long ribbon- 
 like body, which in its external appearance recalls to some extent the 
 strap-worms of fishes. This is especially true of those forms which Die- 
 sing has included in his well-known "Systema Helminthum" 2 under 
 the title of Ligula reptans, although, from variations in their size (in 
 some cases a foot long), and from the variety of their hosts, they would 
 seem to be representatives of very different species. So far as Diesing 
 knew them, these forms were all derived from parasites occurring in 
 various animals (mammals, birds, reptiles, and especially snakes), 
 usually in the connective tissue of the hypodermis and of the muscles, 
 and in snakes frequently free in the body-cavity, or below the peri- 
 toneal membrane. I have examined a number of these worms (among 
 them one from Lulra brasiliensis, which Diesing also cites, a second 
 from a Floridan bird, and a third from Cryptobranchus japonicus), and 
 can distinctly affirm that they are not ligulidte, but, like Bothrio- 
 cephalus liguloides, represent the young stages of certain Bothriocepha- 
 lidse. Diesing himself afterwards referred his Ligula reptans, with 
 some related forms, to a specially erected genus, fiparganum, 3 and 
 expressly described them as larval stages of Dibothrium, Diesing 
 ( Bothriocephalus). 4 ' Cobbold also, in describing his Ligula Mansoni, 
 recalls the Ligula reptans and the L. nodosa of the trout (p. 715), 
 associated by Bertolus with B. latus, and has no hesitation in regarding 
 his worm as a larval form, and even thinks it possible that it may 
 originate from B. latus, so that its occurrence in man would be com- 
 parable with that of Cysticercus. On the whole, however, he is more 
 
 1 See especially the inaugural dissertation of my pupil Kiessling, " Ueber den inneren 
 Bau des Schistocephalus dimorphu8 u. Ligula simplicissima, " Archiv f. Naturyesch., 
 Jahrg. xlviii., Bd. i., p. 241, 1882. 
 
 2 Vol. i., p. 581. 
 
 3 "Ueber eine naturgemasse Vertheilung der Cephalocotyleen," Sitzungsb. d. k. Akad. 
 d. wiss. Wien, Bd. xiii., p. 570, 1854. 
 
 * "Revision d. Cephalocotyleen," ibid., Bd. xlviii., p. 249, 1864. 
 
DISPOSITION OF THE ORGANS. 749 
 
 inclined to connect it with Ligula, especially because of the longi- 
 tudinal furrow in the median line of one surface of the body, which 
 he collates with the sulcus longitudinalis, regarded by the descriptive 
 helminthologists as characteristic of the genus Ligula. To this I shall 
 afterwards refer, only noting here that the sulcus longitudinalis of 
 Ligula is brought about only by the thick ventral line of genital 
 apertures, and cannot therefore occur in the worm under discussion, 
 nor indeed in any of Diesing's larval genus Sparganum. 
 
 The parenchymatous, or, as we said in our diagnosis, fleshy con- 
 sistency of this worm is chiefly the result of the connective-tissue 
 matrix, which forms by far the greatest portion of the larval body. 
 No cellular texture is demonstrable. It is a homogeneous mass of 
 clear appearance, by no means compact, and resembling a gela- 
 tinous material rather than the ordinary connective tissue. The 
 uniform appearance is only interrupted by deposits small, tolerably 
 abundant, uniformly scattered calcareous corpuscles by muscle-fibres, 
 
 FIG. 403. Transverse section through the larval body of 
 Boihriocephalus liguloides. 
 
 and by vessels. Other organs, and especially generative organs, are 
 absent, except two nerve cords, which a careful examination of cross 
 sections reveals on the borders of the middle third of the body, as in 
 B. latus. The structure of the muscular apparatus is especially charac- 
 teristic in its deviation from that of the adult Bothriocephalw. There 
 is no division into cortical and median layers, for there is no develop- 
 ment of a distinct transverse or circular musculature, such as occurs 
 in all other Cestodes. This worm possesses, indeed, numerous strong 
 muscle-strands, but, with the exception of those beneath the cuticle, 
 they all run longitudinally, and never combine in large masses. Single 
 bundles, formed by the grouping of fine refringent fibres, run parallel 
 to one another, separated by larger or smaller intervals. These bundles 
 are thickest near the nerve cords, where the parenchyma is more com- 
 pact, forming distinct longitudinal strands, 1 which can be traced in 
 transverse sections along the whole length of the body. We have 
 here the explanation of the fact that the middle of the body-surface, 
 
 1 It was apparently in reference to these longitudinal tracts that Diesing said of his 
 Ligula rcptans (loc. *.)" Tractus intestinalis bipartiti crura parallela in nonnullis saltern 
 individuis conspicua." 
 
750 DESCRIPTION OF BOTHRIOCEPHALUS LIGULOIDES. 
 
 * 
 
 between these strands, is often caused to sink in on either side by the 
 action of dehydrating fluids. To the longitudinal furrow of variable 
 length which thus results, Cobbold has erroneously attached too much 
 importance. Similar, usually smaller, furrows are not unfrequently 
 formed, as Cobbold has also figured, on the outer side of the muscle- 
 strands. On the broad anterior end of my specimens there were a 
 number of longitudinal furrows, which, as was shown by examination 
 of similar stages in other species (I was unwilling to sacrifice my single 
 specimen of Sparganum from the human subject), were associated with 
 the muscle-bundles into a number of stronger strands, serving apparently 
 for the retraction of the head (Fig. 390, A ). While these muscle-bundles 
 extend within the parenchyma for a long distance without special 
 change, they exhibit on the surface of the worm, below the usual cuticle, 
 a marked deviation, repeatedly dividing, ramifying, and reuniting to 
 form a more or less regular plexus, the strands of which often pursue 
 a transverse course, and thus replace the otherwise absent circular 
 muscles. With these strong bundles numerous isolated fibres are 
 associated, which branch off from the former, dividing here and there, 
 and penetrating the clear parenchyma at intervals in all three dimen- 
 sions of space. By their fineness and isolated course they recall the 
 sagittal fibres in the muscular layer of the Tccnicc, except that they 
 extend not only dorso-ventrally, but also transversely and longi- 
 tudinally. 
 
 In contrast to the generally weakly developed musculature, the 
 vascular apparatus attains considerable development. In investigating 
 preserved specimens of Bothriocephalus lotus and B. cordatus traces of 
 the excretory system are only occasionally seen ; in this worm, how- 
 ever, a section cannot be made in any direction without exhibiting 
 numerous vessels of considerable calibre. In transverse sections alone 
 some thirty can be counted without difficulty. They are, of course, 
 especially sections of longitudinal vessels, which are, as is well known, 
 much more abundant in the Bothriocephalidse than in the Trcniadae, 
 and which penetrate the parenchyma of the body superficially as well 
 as deeply. They seem to be specially developed near the nerve cords 
 and the adjacent longitudinal muscle-strands. It is not, however, 
 merely in the number of longitudinal vessels that the vascular system 
 of this worm recalls that of Bothriocephalus, but also in the splitting 
 and anastomosis by which a distinct network is formed, with meshes 
 of considerable but variable width, and usually of rhombic form. The 
 vessels have no special external walls ; their boundaries are formed 
 by the common ground substance, so that they are to be considered 
 merely as lacunar passages. In spite of this, the fine muscular fibres 
 are not unfrequently disposed in a distinctly developed annular 
 
STRUCTURE OF THE HEAD. 751 
 
 manner, which is probably not without influence on the width of the 
 vascular spaces. 
 
 The great histological differences between the ribbon-shaped body 
 of this worm and the subsequent chain, furnish sufficient evidence 
 that the former is not directly metamorphosed into the latter, but, 
 like the body of Cysticercus fasciolaris, is lost in the transition to the 
 final state, and is replaced by a new formation. The same is probably 
 true of related forms with longer larval bodies. In all probability the 
 head and the immediately adjacent portion persist to form the origin 
 of the jointed body. 
 
 The constitution of the head is but little known. Cobbold gives 
 no report on the subject ; his specimens apparently had their heads 
 wholly retracted, and in mine the latter is only half protruded. So 
 much, however, I may affirm, that the head has an 
 unusually compact appearance. It appears in my 
 specimen as an almost hemispherical protrusion, 
 which is traversed on either side by a superficial 
 furrow. Both furrows can be traced to the hole 
 occupying the apex of the protrusion, and are there- 
 fore not free throughout their whole length. There 
 are no distinct lips unless one can so regard the 
 ridge-like protruding boundaries of the furrow. The F IG . 404. _ Head 
 state of affairs further forward I was forced to leave ?? Bothrwcephalus 
 
 , . , , hguloides. (x 5.) 
 
 undecided. 
 
 The life-history also of this parasite is still unknown. We are 
 left to mere conjectures that the host of the adult worm is a car- 
 nivorous animal which comes into close association with man. It 
 may be likewise presumed that man is not the only host of this form. 
 It seems likely that the dog or cat, or even the pig, 1 is in some way 
 implicated in the history of this parasite. That it occurs also in cold- 
 blooded animals is, considering the great difference in the conditions 
 of life, as probable as the supposition that the host of the adult worm 
 is likewise cold-blooded. 
 
 1 The pig is not, indeed, a domestic animal throughout Japan, but, according to my 
 Japanese pupils, is kept in the island Kiushiu, where the host above referred to was 
 probably infected, and in the whole province of Satsuma, to which the island belongs. 
 
INDEXES. 
 
GENERAL INDEX. 
 
 PAGE 
 
 Abildgaard on Bothrtocephalus, . 32 
 
 on Schistocephalus, . 39 
 
 Abyssinians, disgusting habits of, . 473 
 
 ,, Frequency of Tcenia in, 165 
 
 Raw flesh eaten by, . 156 
 
 Acanthobothrium coronatum, . 372, 374 
 
 Acanthocephali, relation of to Nema- 
 
 todes, ..... ... 110 
 
 Acanthotheci, . , ; . 267 
 Acephalocystis, . . . . 584 
 
 Accela, 109 
 
 Acute Cestodic tuberculosis, . 133, 467 
 Allantonema mirabile, . . . 2, 98 
 Attoioncma (= fihabditis) appcndi- 
 
 culatum, 95, 96 
 
 Alternation of generations, . 2, 272 
 
 ,, Discovery of, '.- 33 
 
 in Distomidse, . 117 
 
 Amoeba, ... . 179 
 
 Definition of, . , . 185 
 
 buccalis, . . 187, 241 
 
 coli, definition of, . 186 
 
 dentalis, . 187 
 
 Jelaginia, . . 189 
 
 polypodia, . .189 
 
 princeps, . . 189 
 
 Amphiline, . . 268, 329 
 
 Amphimonas ( = Bodo), . . 243 
 
 Amphiptyches, . . 106, 268, 276 
 Amphistomum subclavatum, life-his- 
 tory of, ..... 80 
 
 Andry, 408, 410 
 
 Aneurisms due to parasites, . . 74, 131 
 
 Anguittula intestinalis, . . 2, 126, 141 
 
 ,, stercoralis, . . 2, 48, 198 
 
 ,, ,, Young of, . 49 
 
 Anthelminthics, action of, . . 149 
 
 Anthoccphcdus, .... 369 
 
 ,, gracilis, . . . 370 
 
 Antkomyia canicularis, . . . 2, 15 
 
 ,, Symptoms due to, 143 
 
 Antilopc bubcdis, . . . . 137 
 
 Aphylles, 388 
 
 A rcclla parasitic in man (?), . . 184 
 Archigetcs, . . 90, 115, 376, 378 
 
 ,, Direct development of, 
 Arctomys Ludoviciana, . 
 Arion ater, parasite of, . 
 Ascaris, boring of, . 
 
 ,, incisa, 
 
 ,, inflexa, 
 
 ,, intestinalis, 
 
 70 
 405 
 95 
 138 
 67 
 98 
 98 
 lumbricoides, 48, 56, 66, 146, 667 
 
 Ascaris lumbricoides, vitality of eggs 
 
 of, .... 54 
 
 meqalocephala, . . 11 
 
 Kfl fi'7 
 
 mystax, ... oo, bb/ 
 nigrovenosaSee Ehabdonema. 
 
 suiUce, .... 154 
 
 vesicular is, . . 98 
 
 Aspidogaster, . . . . 90, 115 
 
 ,, Direct development of, 70 
 
 Astacobdetta, 107 
 
 Aulastomum vorax, . . . 107 
 
 Aurelia, . . . . V 273 
 
 Autochthones, ... . . 154 
 
 Bacillus anthracis, . - 
 
 butyris, . -. 
 ,, comma-, 
 Bacterium termo, . 
 Baer, K. E. von, on Redia, 
 
 Definition of, 
 
 coli, . 
 
 Definition of, 
 Infection by, 
 
 180 
 180 
 181 
 180 
 30 
 253 
 254 
 148 
 254 
 262 
 
 Pathological results of, 264 
 Reproduction of, 260 
 Structure of, . 257 
 entozoon, . . . 261 
 BdeUura parasitica, . . . 108 
 Beneden, Ed. van, . . . 9, 11 
 on Gregarines, . 194 
 
 ,, on tape-worms of fish, 38 
 
 Benedenia, .... 198, 219 
 Berthold on Pseudoparasites, . 3 
 
 BUharzia See Distomum hcematobium. 
 Bladder- worm, . . . . 385 
 Age of, ... 384 
 Calcification of, . 385 
 Connective-tissue capsule 
 
 of, ... 359 
 Death of, . . 385 
 Degeneration of, . 83, 88 
 Development of, . 340 
 Development of head of, 345 
 Form of, . . 355 
 Formation of fluid in, 343 
 Loss of the caudal 
 
 bladder, . . 381 
 Me*gnin's theory on, 403 
 Morphological position 
 
 of head of, . . 362 
 Moulting of young, 345 
 
 Parenchymatous, . 343 
 
756 
 
 GENERAL INDEX. 
 
 Bladder- worm, Physiological significance 
 
 of the cyst, . . 369 
 
 Polycephaly of , . 356 
 
 Size of, ... 355 
 
 ,, Wandering of, in brain, 359 
 
 ,, See also Cosnvrus, Cysti- 
 
 cercus, Echinococcus. 
 
 Bloch on parasites of the bustard, . 10 
 
 ,, on Ligula, . . . 25 
 
 Bvdo intestinalis, . . . 241 
 
 ,, saltans, . . . . . 241 
 
 ,, socialis, .... 241 
 
 ,, urinarius, .... 241 
 
 Boerhaave on origin of Helminths, 24 
 
 Bellinger on Strong ylus cquinus, . 131 
 
 Bondlia, parasitic male of, . . 10 
 
 Bonnet on Tania lota, . , . 413 
 
 Boring apparatus of embryos, . 62 
 
 of parasites, . 138 
 
 Bostrickus 123 
 
 Bothriocephalidse, ... 388 
 
 Definition of, . 674 
 Development of, . 376 
 Distribution of, . 681 
 Excretory organ* of, 679 
 Generative organs of, 680 
 Glands of, . . 678 
 Grooves of, . 676 
 Muscles of, . 677 
 Nerves of, . . 679 
 ,, Reproductive organs 
 
 of, . . . 680 
 Bothriocephalus, . 369, 375, 388, 748 
 Definition of, . 682 
 
 Eggs of, . . 59 
 
 ,, Peculiarities of gener- 
 
 ative organs of, 31 8 
 
 Species of, . . 682 
 
 cordatus, . . 390 
 Definition of, 736 
 
 ,, Steenstrup's case of, 738 
 cristatus, definition of, 735 
 fasciatus, . . 279 
 latus, 12, 25, 32, 56, 
 
 145, 390 
 
 ,, Anatomy of, . 687 
 ,, Braun's researches 
 
 on, . , 719 
 , , Gal oareous corpuscles 
 
 of, . . 690 
 ,, Connective tissue of, 
 
 689 
 
 ,, Cirrhusof, . 694 
 ,, Definition of, 683 
 
 ,, Development of, 714, 
 
 721 
 
 ,, Distribution of, 729 
 Embryo of, . 725 
 , Fertilising canal of, 704 
 , , Genital apertures of, 692 
 ,, Malformations of, 713 
 Muscles of, . 689 
 ,, Nerves of, . 691 
 ,, Occurrence of, 714 
 ,, Ovaries of, . 706 
 
 Bothrioccphalus latus, Reproductive organs 
 
 of, . . 691 
 , , Their development, 710 
 Shell -gland of, 705 
 ,, Size and growth of, 125 
 ,, Supposed direct de- 
 velopment of, 378 
 Testesof, . 699 
 ,, Uterus of, . 701 
 ,, Vagina of, . 700 
 Vas deferens of, 697 
 Vessels of, . 690 
 ,, Young stage of , in 
 
 pike, . 159, 717 
 Hguloides, definition of, 745 
 proboscideus (= B. sal- 
 
 roonw), . 301, 744 
 punctatus, . 680 
 
 salmonis, . 328 
 
 solidus, . . 25, 33 
 
 tctraptcrus, . 279 
 
 tropicus, . 420 
 
 Brain, Cysticerci in, . . 549 
 
 Brama raji, .... 370, 372 
 Braun, researches of, on Bothriocephalus, 719 
 Bremser on preudoparasites, . 3 
 
 ,, Definition of worm disease by, 122 
 on hooks of Tcenia solium, 417 
 
 Brood -capsules, formation of (see also 
 
 Echinococcus), . . . . 610 
 Bulbus of Nematodes, ... 95 
 
 Buratis, filthy habits of, . . 639 
 Burbot (see also Lota vulgaris), . 685 
 
 Bunaria, 253 
 
 Bursarieae, definition of, . . 254 
 
 Bustard, numerous parasites in, 10 
 
 Butschli on TrtcAoaomutn, . . 10 
 
 Calcareous corpuscles of Bothrwcephalus 
 
 lotus, . 690 
 
 ,, ofCestodes, . 281 
 ,, ,, of Cysticercus 
 
 celluloses, . 509 
 
 ,, ,, Development of, 349 
 
 Calcification of Trichina, . . 21 
 
 Calcoglobulin, .... 284 
 
 Caligu*, parasite of, . . , . 107 
 
 Capsule See Connective-tissue cyst, 359 
 
 Carter on the Guinea- worm, . 43 
 Cat, parasites of, . . 12, 47, 80 
 
 Caryophyttceui, 106, 276, 301, 320, 388 
 
 Cell, definition of, ... 177 
 
 Naked, .... 177 
 
 ,, Parasites resembling normal, . 179 
 
 Cercaria, . . . . . 118 
 
 ,, armat-a, . . . 72 
 
 Cercomonas, definition of, . . 240 
 
 acuminata, . . 241 
 
 Uflagettata, ... 241 
 
 globulus, . . 241 
 
 hominis, . . . 244 
 
 intestinalis, . . 250, 251 
 
 Definition of, 242 
 
 musca;, . . 237, 240 
 
 Cestodes, absence of alimentary canal in, 298 
 
GENERAL INDEX. 
 
 757 
 
 PAGK 
 
 Cestodes, Absence of body-cavity in, 280 
 ,, Absence or presence of 
 
 uterine opening in, . 308 
 ,, Affinity of, to Trematodes, 105 
 ,, Albuminiparous gland of, 315 
 ,, Anatomy of, . 279 
 
 ,, Body -parenchyma of, 280 
 
 ,, Calcareous bodies of, 281 
 
 ,, Copulation of, . 310 
 
 ,, Cuticle of, . . 284 
 
 ,, Definition of, . 270 
 
 ,, Development of, . 330 
 
 of hooks in, 351 
 of muscles in, 342 
 of rostellum in, 351 
 of suckers in, 351 
 of vascular 
 
 system in, 349 
 
 Eggs and embryos of, . 321 
 Embryonic development of, 324 
 Escape of embryos from egg, 338 
 Excretory system of, 298, 588 
 Fertilising canal of , . 314 
 Formation of, from bladder- 
 worms, . . . 382 
 Formation of cyst round 
 
 embryo of, . . 340 
 Histological differentiation 
 
 of embryo, . . 341 
 Homology of subcuticular 
 
 layer, . . . 
 ,, Hooks of, 
 ,, Individuality of segments of, 
 ,, Moulting of, 
 ,, Muscular system of, 
 ,, Musculo- dermal layer of, 
 ,, Nervous system of, 
 ,, Porus genitalis of, 
 ,, Proterandry of, . 
 ,, Radiate and bilateral sym- 
 metry of, . 
 ,, Sexual organs of, . 
 ,, Male, . 
 ,, Female, 
 ,, Stages in development of, 
 , , Sterility of first joints of, 
 ,, Subcuticular layer of, . 
 ,, Systematic account of, . 
 ,, Unsegmented, 
 , , Uterus of , . 
 ,, Wandering of embryos of, 
 Chabb- al-Kar'i, . . 272, 409, 
 Chigoe, . . . . 15, 
 Chlorosis ^Egyptiaca, 
 Cholera 
 Ciliary lappets, . . . 302, 
 Ciliata, definition of, 
 Cingulum, ..... 
 
 289 
 287 
 275 
 286 
 291 
 290 
 295 
 309 
 307 
 
 277 
 304 
 306 
 306 
 385 
 383 
 287 
 388 
 275 
 316 
 339 
 411 
 144 
 127 
 181 
 344 
 252 
 411 
 
 Cirrhus of Bothrioceplalus latus, , 
 of Tcenia echinococcus, 
 ., of T. nana, 
 of T. perfoliata, 
 ,, of T. sayinata, . 
 Cleanliness, importance of, . 
 Cloaca of Twnia sayinata, 
 
 694 
 589 
 659 
 310 
 440 
 169 
 440 
 
 PAGB 
 
 Coccidia of various animals, . . 224 
 Coccidium, .... 129,198 
 ,, Definition of, . . 202 
 
 ,, Distinctness of hepatic and 
 
 intestinal, . . 220 
 
 ,, Experiments on, . . 215 
 ,, Formation of spores in, . 212 
 ,, Form of adult, . . 210 
 ,, Incubation period of, . 211 
 Nodules of, ... 206 
 post mortem observation of, 222 
 Results of, . . . 225 
 Structure and development of, 205 
 Wandering of spores of, 217 
 
 oviforme, . . . 198 
 Definition of, . 203 
 ,, Eimer's observa- 
 
 tions on, . 218 
 per for ana, . . . 221 
 Rivoltce, ... 221 
 
 Cochin-China diarrhoea, 2, 10, 48, 98, 125, 141 
 Ccenurus, .... 356, 557 
 in brain of lamb, . . 135 
 Wandering of, in the brain, 359 
 cerebrolis, . . .85, 405 
 
 Colic of horses 131 
 
 Colloid cancer, relation of Echinococcus 
 
 to, 625 
 
 Colonial cysticercoids, . . . 367 
 Cdpoda cucullus, . . . . 253 
 Comma, Bacillus, . . . . 181 
 Commensalism, .... 9 
 
 Conditions of development, . . 56 
 
 Connective-tissue cyst, action of gastric 
 
 juice on, . 75 
 
 ,, of Echinococc-us, 612 
 
 ,, developed round 
 
 Cestode embryos, 340, 359 
 Contagium vivuno, * . 121, 181 
 
 Copulation of Cestodes, . . 310 
 
 Cray-fish, parasite of, . . . 107 
 Crustacea, parasitic, ... 93 
 
 Cryptobranchus japonicus, . . 748 
 Cucullanus, . . . . 101, 119 
 Cunningham on Amoeba in man, . 186 
 Cursor isabellinus, . . . . 366 
 Cuticle of Cestodes, ... 284 
 Cyclops, host of Filar ia mcdincnsis, 160 
 Cyclops serrulatus, . . . 365, 653 
 Cyprinus, . . . . . 715 
 Cyst, connective-tissue See Connective- 
 tissue cyst. 
 
 Cysticercoid stage, possible absence of, 365 
 Cysticercoidei, .... 400 
 Cysticercoids, . ... 360 
 Characters of, . . 653 
 
 Colonial, ... 367 
 Cysticercus acanthotrias, 390, 561, 583 
 
 ,, arionis, . . 361, 654 
 
 bovis, . . . 405, 458 
 , , First successful breed- 
 
 ing of, . . 459 
 ,, Frequency of, . 472 
 
 cdluloaie, . 390, 405, 422 
 Bladder of, . 509 
 
758 
 
 GENERAL INDEX. 
 
 VAGB 
 
 Cysticercus cettulosce, Conditions affect- 
 ing infection by, 
 
 543, 547 
 
 ,, Development of , 499 
 
 ,, ,, Historical account 
 
 of, . . 537 
 ., History of, . 490 
 
 ,, ,, Occurrence of, 11 
 
 ,, ,, in the brain, 549 
 
 ,, in the eye, 550 
 
 ,, ,, in man, . 544 
 
 ,, ,, Pathological effects 
 
 of, 466, 538, 552, 557 
 Structure of, 463,501 
 ,, ,, Successful breeding 
 
 of, . . 491 
 ,, ,, Supposed occur- 
 
 rence in man, 475 
 Viabilityof,483,510,533 
 cydopi*, ... 380 
 ,, ddphini, 
 ,, fatciolarit, 
 
 glomeridi*, . 
 
 Krabbei) 
 
 longicollis, 
 
 lumbriculi, . 
 
 melanocephalus, 
 
 oviparus, 
 
 372 
 355, 382, 404, 
 
 405, 654 
 363, 367 
 405 
 
 356, 405, 504 
 363 
 556 
 498 
 
 pigiformis, 136, 342, 349, 
 
 403, 405 
 
 Wandering of, in liver, 359 
 racemosus, . 357, 554, 628 
 Tcenice cucumerina:, 373, 380 
 talpce, .... 405 
 tnntHid, . ; * 405 
 tencbrionis, . . . 360 
 tenuicottis, 136, 355, 390, 405 
 Daughter-bladders 
 
 in, . . 358 
 
 ,, Experiments on, . 579 
 
 Head of, . 575 
 
 History of, . 564 
 
 Ribbon of, . 676 
 
 ,, Structure of, . 669 
 
 ,, turbinatus, . . . 556 
 
 ., (Piestocystis) variabilis, . 347 
 
 ,, See also Bladder-worm. 
 
 Cystici (Cystic tape-worms), . 390, 399 
 
 ,, Definition of, ... 400 
 
 Cystoidei (ordinary tape- worms) 390, 6.12 
 
 Cystotcenia, . . . 390, 404, 488 
 
 Daughter-bladders, formation of, 
 ,, Internal, 
 
 Intralamellar, 
 
 Da vain e on eggs of Ascaris, . 
 
 ,, on vitality of embryos, 
 Degeneration of bladder-worms, 
 Delphinus delphis, parasite of, 
 Dendrocometes, ... 
 Dermatodectes . . . 
 
 611 
 
 619 
 615 
 154 
 66 
 
 83, 88 
 106 
 235 
 14 
 Dessication, effects of, on eggs of Nema- 
 
 todes, . 53 
 
 . ,, on germs, . 236 
 
 Development, direct, . . 66, 70, 71 
 ,, Duration of capacity for, 337 
 
 of Bothrioccphaluslatu8,714, 
 721 
 
 of Cestodes, . . 330 
 ,, of Eckinococcua, . 594 
 
 ,, of Entozoa, . . 66 
 
 ,, of Tcenia saginata, . 458 
 
 Diathesis venninosa, . . . 122 
 Dibothria. See Bothriocephalidae. 
 Dibothrium See Bothriocephcdus. 
 Difflugia parasitic in man (?) . . 184 
 
 Diphylles, 388 
 
 Diplozoon, . . .... 45, 48 
 
 Dipylidium, . . . 390, 655, 665 
 Direct development of certain species, 70, 71 
 Diseases due to vegetable parasites, 180 
 ,, of host, effect of, on parasites, 123 
 ,, Supposed to be due to para- 
 sites, 120 
 Dislomum, migration of, . . 71 
 echinatum, . . 11, 76, 80 
 ,, haimatobium, eggs of, in 
 
 urinary veins, 47 
 
 ,, ,, Male armature of , 7 
 
 ,, Origin of, . 166 
 
 Parasitic female, 44 
 
 Pathological effects 
 
 of, . . 129 
 
 ,, hepaticum, distribution of, 12 
 ,, ,, Eggs of, . 146 
 
 ,, ,, Ency station of, 
 
 on plants, . 73 
 
 ,, Larvae devoured 
 
 with plants, 81 
 ,, Mode of trans- 
 
 ference of, 46 
 
 ,, ,, Rate of develop- 
 
 ment of, . 56 
 
 ,, Variations in fre- 
 
 quency of, . 164 
 
 ,, /,; D,.-- , . . . .11 
 
 ,, lanceolatum, . . 146 
 luteum, ... 6 
 
 maci-ostomum, . .72 
 Distribution of Bothriocephalidze, . 681 
 of Bothriocephalu* lotus, 729 
 Cases of restricted, . 168 
 ,, of Ttenia eckinococcvs, 632 
 ,, of T. saginata, . . 476 
 
 of T. sdium, . . 535 
 Dochmius duodenalis, 17, 56, 57, 61, 
 
 64, 127, 146 
 
 trigonocephalus, 62, 64, 66, 160 
 Doeveren, van, on distribution of En- 
 tozoa, 27 
 
 Dog, cramp in, . . . , 143 
 
 ,, Death of, from T. ccenurus, . 142 
 
 ,, Effects of taxation on number of, 166 
 
 Parasites of, 12, 46, 47, 80, 152 
 
 Dog-louse (see Trickodectes), . . 160 
 
 Drfcunculus (see also Filaria mcdinen- 
 
 sis) 46, 101 
 
 Duck, parasite of, .... 80 
 
 Dujardin on food of Oxyuris, . 9 
 
GENERAL INDEX. 
 
 759 
 
 Dujardin on Mermis, 
 Dyctylogyrus, 
 
 35 
 
 45, 48 
 
 Earth-worm, parasite of, . . 107 
 
 Echeneibothrium, . . 372, 384, 388 
 
 ,, minimum, 37, 273, 274 
 
 Echinobothrium, . . . . 282 
 
 ,, typus, life-history of, 80 
 
 Echinococcifer, . . . 390, 578 
 
 Echinococcus, absence of muscles in 
 
 bladder of, . . 402 
 ,, Analysis of cyst of, . 630 
 
 ,, Brood-capsules of, . 610 
 
 ,, Case of, with Cercomonas, 
 
 244, 250 
 
 and colloid cancer, . 625 
 Death of, . . . 650 
 Development of, . 594 
 Diagnosis of, . . 149 
 Endogenous, . . 616 
 Experiments with, . 595 
 Fertile and sterile, . 585 
 Fluid contained in, . 613 
 Formation of daughter- 
 bladders, . . 611 
 Frequency of, . . 637 
 General account of, . 578 
 Heads of, . . . 609 
 Intralamellar proliferation 
 
 of 629 
 
 Medical significance of, 643 
 Metamorphosis of head 
 
 into bladder, . . 620 
 Metamorphosis of brood - 
 
 capsule into bladder, 621 
 Multiple occurrence of, 634 
 Occurrence of, . . 641 
 Point of origin of, . 626 
 Proliferation of, . . 357 
 Removal of, . . 150 
 Rupture of, . . 647 
 Statistics of, . 632, 640 
 Sterile and fertile, . 617 
 Structure of cuticle of, 599 
 Structure of heads of, 603 
 
 Thickened cyst of, . 20 
 
 altricipariens, . 583, 616 
 endogena, . . v 616 
 hominis,. . . . 580 
 granulosus, . . 616 
 hydatidosus, . . 616 
 multilocularis, 84,586,611, 
 
 624, 627 
 
 racemosus, . . . 628 
 scolecipariens, . . 616 
 simplex, . . . 616 
 veterinorum, . 580, 612 
 See also Tcenia echinococcus. 
 Echinorhynctius, 11, 33, 65, 76, 119, 324 
 ,, angustatus, . . 18 
 
 ,, gigas, . . 12, 139, 163 
 
 ,, proteus, . . . 398 
 
 Ecker on parasite of rook, . . 47, 49 
 Ectoparasite, definition of, . 16 
 
 Eggs of Cestodes, .... 321 
 
 Eggs of Distomum hepaticum, 
 
 Effect of dessication on, 
 ,, of reagents on, . 
 
 found in man, diagnosis of, . 
 
 of gadflies, .... 
 
 Mode of exit of from host, , 
 
 Stage of development when laid, 
 
 of Tcenia ccenurus, 
 
 of T. cucumerina, 
 
 of T. echinococcus, 
 
 of T. marginata, . ^ 
 
 of T. nana, . . . . 
 
 of T. saginata, . . . 
 
 of T. serrata, . '.. 
 
 of T. solium, .. 
 
 voided with urine, 
 -shells dissolved by gastric juice, 
 Ehrenberg on Infusoria, 
 Eimer on Coccidium oviforme. 
 
 PAGE 
 146 
 
 53 
 54 
 146 
 78 
 46 
 55 
 568 
 672 
 590 
 568 
 660 
 449 
 568 
 528 
 46 
 
 Egg-shells dissolved by gastric juice, 59 
 Ehrenberff on Infusoria, . . 177 
 
 218 
 
 198, 220 
 
 Elastic cushion of Nitsche, . 393, 401 
 Embryo of Cestodes, ... 385 
 Ciliated, of Bothriocephalus, 338 
 ,, Course of wandering of, 339 
 ,, Escape of, from egg, . 338 
 Histological differentiation 
 
 of 341 
 
 of parasites, . . .' 44 
 Encystation, . . . . 19 
 
 Entoconcha mirabilis, ... 91 
 
 Entodinium, . . . . . 253 
 Entoparasite, definition of, . 16 
 
 Entozoa, definition of, . . . 13, 16 
 Ephemera, Gordius parasitic on, . 63 
 
 Epizoa, definition of, . . 16 
 
 Ercolani on Filaria mitis, . . 52 
 
 Eschricht on metamorphosis of Entozoa, 32 
 
 Euglena, 249 
 
 Eustrongylus gigas in Nasua, . 128 
 
 Excretory organs of Bothriocephalidae, 679 
 ,, of Bothriocephalus latus, 690 
 
 ,, of Cestodes, . 298, 588 
 
 ,, Development of, . 344 
 
 ,, of Tcenia echinococcus, 
 
 588, 601, 604 
 
 of T. saginata, . 437 
 Eye, Cysticerci in, . . . . 550 
 
 Fasciola See Distomum. 
 Fedschenko on the Guinea- worm, . 160 
 Felis concolor, Tcenia echinococcus in, 591 
 Fertilising canal of Bothriocephalus 
 
 latus, . . 704 
 of Cestodes, . 314 
 ,, of Tcenia saginata, 445 
 
 Fertility, extraordinary, of Nematodes, 43 
 Fiery serpents, . . , . 168 
 Filaria, vitality of, . . . 157 
 attenuata, . . .49, 51 
 
 Bancrofti See F. sanguinis 
 
 hominis. 
 
 immitis, . . . , 49 
 
 leporis pulmonalis, . -. 47 
 
 loa, 140 
 
 medincnsis, diagnosis of, . 148 
 
760 
 
 GENERAL INDEX. 
 
 PACK 
 
 Ftfaria medincnsis, Fertilisation of, 43 
 
 ,, Larva found in Cyclops, 
 
 77, 160 
 
 ,, Pain caused by move- 
 
 ments of, . 140 
 ,, Periodic occurrence of, 164 
 
 ,, , Supposed poisonous 
 
 properties of, . 134 
 ,, Treatment of, . 150 
 
 ,, Ulceration due to, 138 
 
 ,, Vitality of embryos 
 
 of, . . . 54 
 
 ,, piscium, . . . . 157 
 ,, sanguinis hominis, 46, 50, 127, 
 
 140, 166 
 
 ,, sanguinolenta, . . 47, 49, 76 
 FUaroides mustdarum (= Spiroptera 
 
 nasicola), ..... 143 
 Flagellata, definition of, . . 237 
 Flea, larva of, . . . . 60 
 
 Fox, parasite of, . . . 12 
 
 Frog, parasites of, ... . 19,80,184 
 
 Gastric juice, action of, on cysts of 
 
 Entozoa, 75 
 
 ,, on egg-shells, 58 
 Gastropacha ncustria, parasites in cater- 
 pillar of 63 
 
 Gastrw equi, . . . 8,15,79 
 
 Generatio aequivoca, . . . 22, 591 
 Generative organs of Bothriocephalidae, 680 
 ,, of Bothriocephalus 
 
 latus, 691, 694, 700 
 of Cestodes, . 304, 306 
 of Tcenia comurus, 314 
 of T. cncumeriua, 671 
 of T. echinococcus, 589 
 of T. perfoliata, 310,313 
 of T. saginata, 438, 441 
 of T. seligera, . 311 
 of T. solium, . 525 
 of T. uncinata, . 312 
 Germ-gland See Ovary. 
 Giard on Orthonectida, . . . 117 
 Glaucoma scint'Mans, . . . 254 
 
 Glomeris, 363 
 
 Goblet cells compared with Protozoa, 176 
 
 Gonospora tercbettce, . . . 194 
 
 Gordius in rain water, . . 35 
 
 ,, Life-history of, . 79 
 
 ,, Migration of, . . . 63 
 
 ,, Peculiarities of, . . 112 
 
 Gorilla, parasites in, . . . 173 
 
 Gb'ze on a case of numerous Entozoa, 1 
 
 on a dog affected by Tcmia cucu- 
 
 merina, . . ... 143 
 
 on two human tape- worms, . 416 
 Grand-nurse, . . . . 386 
 
 Grcgarina, . ... ... . . 192 
 
 cuneata, . . . 192 
 
 gigantea, . . . 191 
 
 Gribbohm on statistics of Entozoa, 123 
 
 Grooves of Bothriocephalidae, . 676 
 
 Gruby and Delafond on Filar ia son- 
 
 guinolcnta, . . . , 49 
 
 Guinea-worm See Filaria medincnsis. 
 Gymnorhynchus reptans, . . 370 
 
 Gyporhynchus, . ., 364, 373, 635 
 
 Hzematozoa, instances of, . . 49 
 
 in mosquito, . . 64 
 
 ffcemopis vorax, . . . . 144 
 Head, development of, . . . 345 
 Evagination of, . . 353 
 
 of Bothriocephalidae, . . 677 
 of Cysticercus cellulose, . 463, 502 
 of C. tenuicollis, . . . 575 
 of Tcenia echinococcus, . 586, 603 
 of T. saginata, . . 433 
 
 of T. solium, ... 520 
 of tape-worm, significance of, 273 
 
 Head-rudiment, .... 345 
 Heart, Nematode parasites in, . 49 
 
 Heart- worms, . . . . 121 
 Heat necessary for development of eggs, 50 
 Hedgehog, parasite of, . . , 12 
 
 Hedruris, . ... . 119 
 Helcophagi, . . . . .23 
 Helminthological experiment, instances 
 of successful, 124, 133, 
 
 3*9, 460, 491, 595, 720 
 Introduced by Klichen- 
 
 meister, . _ . . , 336 
 Objections to, . ; ,. 337 
 
 Helminths, list of human, . . 145 
 Heterogeny, . . . , .24 
 
 ffcxamita intestinalis, 
 Hibernation of host, 
 
 parasite, .... 
 Hippobosca, .... 
 Ifolophrya, . . 
 Holostomum excavatum, . 
 Hooks, development of, 
 
 Embryonic position of, 
 
 Metamorphosis of, 
 
 of Cestodes, 
 
 of Tania acanlhotrias, 
 
 of T. ccenurug, 
 
 of T. crassicollitt, 
 
 of T. echinococcus, 
 
 of T. marginata, . 
 
 of T. nana, . 
 
 of T. serrata, 
 
 of T. solium, 
 
 of Taeniadse, 
 
 Varying numbers of, 
 Horse, aneurism in, 
 
 ,, Herpetic disease of, 
 Nematodes, . 
 
 Parasites of, . 8, 9, 11 
 Host, definitive, .... 
 
 ,, Intermediate, origin of, . 
 
 ,, Suitable and unsuitable, 
 Huxley on origin of Helminths, 
 Hydatid tremor, .... 
 Hylobius pin i, parasite of, 
 Hymenolepis, 
 
 Hypochondriasis taeniosorum, 
 Hypomcneuta cognatetta, parasites in, 
 JfypudwusSve Shn-w. 
 
 240 
 effect of, on 
 
 75 
 
 ... 5 
 259 
 11 
 351 
 361 
 287 
 287 
 562 
 567 
 
 392, 524 
 581, 587, 607 
 567 
 658 
 566 
 523 
 392 
 330 
 74 
 to 
 
 144 
 12, 15 
 73 
 115 
 
 . 85, 86 
 109 
 612 
 
 , 2, 98 
 390, 657 
 487 
 63 
 
 524, 
 
 due 
 
GENERAL INDEX. 
 
 761 
 
 PAGE 
 
 Icelanders infested by Echinococcus, 166 
 Ichneumonidae, eggs of, laid in cater- 
 pillars, 78 
 
 Idiogenes otidis, . . . . 384 
 Individuality in Cestodes, . 271, 386 
 Infection by Cysticercus celluloses, con- 
 ditions affecting, 543, 547 
 by food, ... 156 
 Generally passive and acci- 
 dental, ... 161 
 How affected by age, . 162 
 Locality, . 164 
 Occupation, . 163 
 Season, . 164 
 Sex, . . 163 
 Modes of, . . 65 
 Infusoria, definition of, . . . 228 
 Fission in, , . 236 
 Nucleolus of, . . 234 
 Nucleus of, . . . 232 
 Reproduction of, . . 233 
 Invertebrata, mature parasites of, . 115 
 Irritation due to parasites, . . 141 
 Isotricha intestinalis, . . 253 
 
 Kahane on parasite of crows, . 49 
 
 Kangaroo, parasites of, . . . 12, 140 
 Kidney-worm (Stephanurus), . . 46 
 
 Kingsyellow worm, ... 30 
 
 Klossia, . . . . .- 198, 219 
 Knox on epidemic in Kaffir war, . 168 
 Krabbe on Cysticercus tenuicollis, . 152 
 ,, on Echinococcus, . . 151 
 Krehl on etymology of Solium, . 411 
 Kiichenmeister on development of Ces- 
 todes, . . 331 
 ,, discovers connection 
 
 between bladder- 
 worms and tape- 
 worms, . . 38 
 ,, on Tcenia mediocancUata, 420 
 
 Lacerta agilis, Entozoa in embryos of, 67 
 
 ,, vivipara, . . . . 343 
 
 Larva of flea, .... 60 
 
 Larval forms, varieties of, . . 59 
 
 Leech, 17 
 
 Lcpidopus, ..... 380 
 
 Leptodera, . . . . . 94 
 
 Lerncca, . . . . . 43 
 
 Lernseadse, ..... 93 
 
 Leuckart, F. S., on origin of parasitism, 91 
 
 Leuckartia, . . . . . 317 
 
 Lcucochloridium paradoxum, . . 72 
 
 Lewis on Nematodes in blood, . 50 
 
 Lieberkiihn on psorosperms, . . 196 
 Ligula, 11, 25, 33, 139, 309, 317, 320, 
 
 376, 379, 388 
 
 ,, Mansoni, .... 745 
 ,, nodosa, . . . , 715 
 ,, reptans, .... 748 
 ,, simplicissima, . . . 747 
 Ligulidae, . . . . . 378 
 Lindeinann on psorosperms in the kid- 
 ney, 226 
 
 Lindemann on psorosperms on the 
 
 hair 226 
 
 Liparis chrysorrhoea, parasites in cater- 
 pillar of, 63 
 
 Longevity of parasites, ... 87 
 
 Lophius piscatorius, . . 372, 374 
 Losch on Amoeba coli, . . . 187 
 Lota vulgaris, . . . 685, 717 
 Lubbock on Sphcerularia, . . 115 
 Lucilia, . ... 144 
 
 ,, hominivora . . . 15 
 
 Lumbricus latus, . . 408, 413 
 
 Lutra brasiliensis, . . . 748 
 
 Lymnceus pereger, , . . 363 
 
 ,, stagnalis . , 72 
 
 Malformations of JBothriocephalus latus, 713 
 ,, of Tcenia ccenurus, 396,399 
 
 of T. saginata, . 499 
 
 of T. solium, . . 518 
 
 Mallophaga, 17 
 
 Man, parasites found in, . .15, 173 
 Manson on haematozoa in the mos- 
 quito, . , . 64 
 ,, on Nematodes in the blood, 50 
 Martin, parasite of, . . . 12 
 Maw-worm See Oxyuris vermicularis. 
 Medical significance of Bothriocephalus 
 
 latus, . 735 
 of Tcenia echino- 
 
 coccus, . 643 
 of T. saginata, 487 
 
 of T. solium, . 535 
 
 Megnin on direct development of 
 
 Tseniadae, 403 
 
 Mehlis on embryos of Trematodes, 
 Mehlis' body See Shell-gland. 
 Meissner on embryos of Gordius, . 63 
 
 Meloidae, life history of, . . 61 
 
 Mermis, migration of, . . 35 
 
 Metamorphosis of Entozoa, universality 
 
 of, . . . ,, . . ' 57 
 
 Micrococcus, . . .> . . 398 
 
 Miescher's tubes, . . . . 1 99 
 
 Migration of Cercaria armata, . 72 
 
 ,, to definitive host, . . 73 
 
 ,, of embryos, ... 67 
 
 ,, Passive, ... 65 
 
 ,, Second, ... 71 
 
 ,, Univers-tlity of, . 49 
 
 Moisture, necessity of, for development 
 
 of Helminths, . . . . 54 
 
 Monadacomonas, . . 243 
 
 Monas crepusculum, . . . 241 
 
 elonyata, . . . . 241 
 
 ylobulm, .... 241 
 
 lens, 241 
 
 Monera, . . . . 175, 182 
 Moniez on the development of bladder- 
 worms, ..... 354 
 Monostomum mutabUe, discovery of 
 
 Cercaria in, . . . 30 
 
 Monocelis caudatus, . . . 108 
 
 protractilis, . . . 108 
 
 Monocyxtis agilis ( = M. lumbrici), 392, 193 
 
'62 
 
 GENERAL INDEX. 
 
 PACK 
 
 Morbi animati, . . . . 121 
 
 Mosquito, haematozoa in, . . 64 
 
 Moulting of bladder-worms, . . 34tf 
 
 Mouse, parasite of, . . . 80 
 
 Miiller, Johannes, on EntoconcJia, . 91 
 
 Mummified tape-worms, . . 485 
 
 Musca (Lucilia) hominivorax, . 144 
 vomitoria, . . 2, 15, 16, 144 
 
 Muscles of Cestodes, ... 342 
 
 of head, .... 294 
 Structure and arrangement of, 291 
 Mustela, parasites of, . 
 
 Mustelus Icevis, Entozoa in foetus of, 67 
 
 My coder ma aceti, . . . . 180 
 
 Myxomycetes, . .. 185 
 
 Naja haje, Pentastomum in, . . 144 
 
 Nasua socialis, . . . . 1 29 
 
 Necessary parasite, . . . 30, 179 
 
 Nematodes, free and parasitic, . 94 
 
 Life-histories of, . . 61 
 
 ,, Resistance of eggs to 
 
 dessication, . . 53 
 (See also the various Genera.) 
 
 Nervous system of Bothriocephalidae, 691 
 
 ,, of Cestodes, . . 295 
 
 Nurse, 35, 273, 380 
 
 Nyctithenw, 253 
 
 (Estrm ovis 15 
 
 Ottulanus, 47, 134 
 
 Onchorhynchu* Hubert, . . . 717 
 Perryi, 717 
 
 Opalina 263 
 
 Operculum, presence of. in certain eggs, 59 
 Ophiuroids, parasites of, . . 117 
 Origin, supposed, of Tcenia echinococcus 
 
 from intestinal villi, . . . 591 
 Ophryoscolex, .... 253 
 Omithomyia, . 5 
 
 Orthonectida, . . . . 117 
 Osmosis, feeding by, . . . 18 
 
 Ovaria ambulantia, . . . 274 
 Ovary of Bothriocephalus latus, . 706 
 of Cestodes, ... 306 
 
 of Tcenia echinococcvs, . . 590 
 of T. nana, .... 660 
 of T. saginata, . . . 443 
 of T. sdium, ... 526 
 Ox, parasites of, . . . 12, 47, 80 
 ,, Parasites derived from, . . 156 
 Oxyuris, migration of, . . . 98 
 
 Self-infection by, . . 154 
 curvula, . . . 9, 11 
 
 vermicularis, 12, 35, 48, 56, 
 
 141, 146 
 
 Pagenstecher on body- cavity in Tcenia 
 
 critica, . . . 280 
 ,, on development of Dis- 
 
 tomes, . 139 
 
 Pallas on origin of parasites, 
 Paludina, parasite of, 
 Panhistophyton, . 
 Paramcecium aurelia, 
 
 26 
 
 80 
 
 398 
 
 231 
 
 PAOR 
 
 Paramcecium coll, .... 253 
 Parasites, abbreviated development of, 100 
 Attachment of, 7 
 
 ., Definition of, 1 
 
 j, Difference of effects of, . 124 
 Distribution of, . .13,161 
 ,, Duration of life of, . 87 
 
 Effects of, . . 120, 125 
 Effect of cooking on, . 157 
 ,, of eggs of, . . 128 
 
 of age of host, . 162 
 
 Food of, ... 17 
 
 ,, General life -history of, . 80 
 
 , , History of knowledge of, 22 
 
 Influence of environment on, 84 
 ,, Instances of abundant, . 10 
 
 ,, In very young children, 167 
 
 ,, Irritation due to, . . 141 
 ,, Life-history of, . . 42 
 
 ,, Locomotion of, 5 
 
 ,, Loss of tissue caused by, 125 
 ,, Mature, in In vertebra ta, 115 
 Migration of See Migration. 
 Necessary, . . . 179 
 Number of human, . 173 
 Occurrence of, . . 10, 161 
 Origin of, from eggs, . 26 
 
 ,, by heterogeny, 24 
 ,, by inheritance, 26 
 Periodic, ... 77 
 
 ,, Predisposition to, . . 123 
 ,, Rarity of, in Invertebrata, 115 
 ,, Relation of, to hosts, . 12 
 
 ,, Respiration of, . . 13 
 
 Statistics regarding, 151, 162, 
 
 165, 168, 530, 540, 548, 632, 640 
 ,, Supposed good effects of, 121 
 ,, Systematic account of, . 171 
 ,, Theories regarding, . 22 
 
 Wanderings of, . .70,132 
 Parasitic diseases, Diagnosis of, . 145 
 ,, Etiology of, . 151 
 
 ,, Treatment of, . 149 
 
 Parasitism, classification of, . . 89 
 
 ,, Complete, of Trichina, 103 
 
 ,, Conditions of, 3 
 
 Constant, ... 2 
 
 of different sexes, . 44 
 
 of female on male, 45 
 
 of male on female, 10, 44 
 Nature of, . . . 1, 3 
 Occasional, ... 2 
 
 Origin of, in Animal King- 
 dom, . . . 89 
 ,, Periodic, - . 4 
 ,, Permanent, . . 4 
 ,, Progress of, in Distomidae, 118 
 ,, Stationary, ... 4 
 ,, Structure correlated with, 5, 16 
 ,, Temporary, * . 4 
 Parrot, Parasites of, . . 10 
 Pathological effects of Cysticercus cettu- 
 
 loscc, 538, 552, 557 
 ,, of Tcenia echinococcus, 643 
 
 ,, of ,, sayinata, 487 
 
GENERAL INDEX. 
 
 763 
 
 Pathological effects of Tcenia solium, 
 Pediculus capitis, .... 
 
 PAOE 
 
 535 
 12 
 
 7, 11 
 of walrus, . . . 13 
 
 Pelodera, 94 
 
 Penis See Cirrhus. 
 
 Pentastomum referable to the Arach- 
 
 nida, ... 14 
 
 ,, Chitinous balls of male, 463 
 
 ,, constrictum, Effects of, 137 
 
 ,, denticulatum, immature 
 
 form of P. 
 tcenioides, 41 
 Effects of, . 137 
 ,, ,, Occurrence of, 77 
 
 ,, ,, Wanderings of, 136 
 
 ,, tcenioides, caries due to, 144 
 
 ,, ,, Eggs of, . 55 
 
 ,, ,, Migration of, 
 
 46, 77 
 Perforation of alimentary canal by 
 
 Entozoa, . . 77 
 
 ,, of viscera by Echinococcus, 647 
 
 Phoca barbata, . . ... 738 
 
 Phthirius See Pediculus. 
 
 Phyllobotkrium, . . 372, 388 
 
 ,, lactuca, . .372 
 
 Phylloxera, ... .123 
 
 Piestocystis, ... . 655 
 
 Dithyridium, . 343 
 
 variabiliis, . 343, 347 
 
 Pig, JBalantidium coli in, . 256 
 
 Pig, parasites derived from, 12, 156 
 
 Pigment in Tcenia saginata, . 436 
 
 Pike, host of Bothriocephalus latus, 
 
 159, 717 
 
 Planarians, as ancestors of Trematodes, 107 
 Planorbis, parasite of, . . 80 
 
 Plasmatic vascular system, . . 303 
 Platodes, definition of, . . . 269 
 
 Podophrya, 235 
 
 Polycephalus, . . . . 405 
 Polyphemus occidentalis, parasite of, 108 
 Polystomum integerrimum, . . 19, 40 
 Pontea cratcegi, parasites in caterpillar 
 
 of, 63 
 
 Pressure on organs, due to parasites, 128 
 Prismatic tape-worms, . . . 453 
 Protoctista, . . . . . 175 
 Proglottides nconati, . . . 668 
 Proglottis, individuality of, . 271, 275 
 ,, Position in life-cycle, . 385 
 Prophylaxis, nature of rational, . 169 
 
 Protista, 175 
 
 Protozoa, 175 
 
 Pseudonavicellse, . . . , 193 
 Pseudoparasite, .... 2 
 
 Pseudophylles, .... 388 
 
 Psorosperms, 398 
 
 ,, formed from Coccidium, 213 
 
 ,, mistaken for eggs of 
 
 helminths, . . 48 
 
 Psorosperm-nodules, . . 205, 209 
 Psorosperm-saccules, . . . 195 
 Pulex penetrans (Khynchoprion), . -43 
 
 Rabbit, Coccidium in liver of, 
 ,, Strongylus commutatus in, 
 , , Tcenia serrata in, 
 , , Trichina spiralis in, . 
 
 Rainey's tubes, 
 
 Rat, Cysticerci in, . 
 ,, Trichina spiralis in, 
 ,, Trichosomum crassicauda in, 
 
 Rate of development, 
 
 Receptacle, . 
 
 Receptaculum scolecis, 
 
 PAGR 
 
 203 
 47 
 135 
 12 
 200 
 128 
 12 
 10 
 56 
 
 346, 503, 576 
 346 
 Receptaculum seminis, of Bothrioce- 
 
 phalus latus, 700 
 of Cestodes, . 313 
 
 ,, of Tcenia echino- 
 
 coccus, . . 590 
 
 ,, of T. nana, . 660 
 
 ,, of T. saginata, . 442 
 
 Redia, . . . .30, 71, 117 
 
 Reproductive organs See Generative 
 
 organs. 
 
 Respiration, aerial, of Entozoa, . 15 
 
 Rhabditis, . . . . 2, 61, 89 
 ,, appendiculata, . . 99 
 
 ,, stercoralis, . . 48, 126, 148 
 ,, terricola, . . .48, 62 
 Rhabditoid larval forms, . . 99 
 
 Rhabdonema, genus created, . . 89 
 
 ,, nigrovenosum, 2, 61, 89, 96 
 Rhizopoda, definition of, . 182 
 
 Rhynchobothrium, . . 369, 388 
 
 Rhynchoprion penetrans, . . 43 
 
 Ribbon -like structure, . . . 576 
 Rook, parasites of, ... 49 
 
 Rostellum, development of, . . 351 
 General structure of, . 401 
 of Cestodes, . . 351 
 
 ofTseniadse, ... 392 
 of Tcenia saginata, v 434 
 of T. solium, . . 521 
 
 Simple, in T. cucumerina, 393 
 
 Sacculina, 18 
 
 ScenolopJius, . . . .^ . 248 
 Scenuris, _ . . . . 115, 376 
 ,, variegata, . . . 363 
 
 Sagitta, Nematodes in, . . . 138 
 Sarcophaga carnaria, larvae of, in man, 
 
 2, 144 
 
 Sarcoptes scabiei, . . . 14, 139 
 
 Schistocephalus, . 139, 309, 317, 376 
 
 ,, solidus, ... 25 
 
 (See also Ligula. ) 
 
 Schizomycetes, parasitic, . . 179 
 
 Schneider, A., on Sphcerularia, . 16 
 
 Sclerostomum armatum, . . . 11 
 
 ,, equinum, 64, 67, 74, 90, 131 
 
 Scolex, .... 371, 373, 385 
 
 ,, polymorphus, . . . 371 
 
 Self-infection, .... 153 
 
 Sexless Entozoa, meaning of, . 35 
 
 Sheep infected by Oestrus, . . 15 
 
 by Trichocephalus, . .66 
 
 by Parasite in bronchus 
 
 of, . . . 46 
 
764 
 
 GENERAL INDEX. 
 
 Sheep, Tamia marginata in, . , 
 Shell-gland of Bothrioceplialus lotus, 
 
 of Cestodes, . . 
 
 of Tcenio echinococcus, 
 
 of T. saginata, 
 
 Shrew, parasite of, 
 
 PACR 
 80 
 705 
 314 
 590 
 442 
 
 48, 356 
 Siebold, C. T. von, on Mermis and 
 
 Gordius, . . 35, 63 
 on migration of Cercaria, 72 
 on "straying" of En- 
 
 tozoa, . . . 37,82 
 on Tctrarhynchus, . 37 
 
 on Trematode develop- 
 
 ment, . . .30, 34 
 107 
 
 681 
 
 411 
 748 
 377 
 179 
 116 
 235 
 119 
 
 11 
 65, 76 
 
 22 
 
 Snail, parasite of, 
 Solium, etymology of, 
 Sparganum, . . 
 
 ,, reptans, . . . 
 Spermatozoa regarded as parasites, 
 Sph&rularia, . ... . 
 
 Spirochona, ..... 
 Spiroptera, . . . . . 
 alata, .... 
 
 murina (= S. obtusa), 
 
 Spontaneous generation, . . 
 
 (See also Generatio aequivoca.) 
 Sporocyst, . . . . 71, 117 
 
 Sporozoa, definition of, . . . 191 
 ,, Name proposed, . . 182 
 Staphylocyets, .... 367 
 Statistics regarding bladder - worms, 
 
 640, 548 
 
 Echinococcut, . 632, 640 
 
 ,, Entozoa in general, . 151 
 
 Nematodes, . . 123, 162 
 
 Taeniadffl, . 165, 168, 530 
 
 Steenutrup on alternation of genera- 
 
 tions, . . .33, 272 
 ,, on Hothriocephalus cor~ 
 
 datus, . . . 738 
 ,, on wandering of Schisto- 
 
 cephalus, . . 25, 139 
 
 Stephanurus, .... 46 
 
 dcntatus (= Sclcrostomum 
 pinguicola), . . . . 
 Stigmata lateralia, . . . 
 
 ,, umbilicialia, . . . 
 Stork, numerous parasites in, . 
 
 Straying of Entozoa, 
 Strobila, .. 
 Strongylus commutatus, 
 
 ,, equinus See Sderostomum 
 
 equinum. 
 
 filaria, . 47, 101, 
 
 gigas, . . . 
 ,, longevag mat us, 
 ,, micrurus, . . 
 ,, paradoxw, . . 
 ,, rufescens, . . 
 ,, tetracanthus, , 
 
 trachealis, . . 11 
 Stylorhynchus oligacanthua, . 
 St. Vitus' dance 
 Suckers, development of, . 
 ,, of Tfvnia cchiwococcus, 
 
 Suckers of T. saginata, 
 
 ,, of T. solium, 
 
 of Tseniadae, 
 Synapta, parasite of , 
 Syngamus See Stronr/ylus trachealis. 
 Synchytrium Mieschcrianum, . 
 Systematic account of the Cestoden, 
 
 PARR 
 
 434 
 
 521 
 
 395 
 
 92 
 
 199 
 
 388 
 
 Tcenia, .... 388, 390, 399 
 ,, a anneaux courts ( = B. latus), 
 
 414, 686 
 
 ,, ,, longs (= T. saginata), 414, 686 
 ,, a dpine ( = Bothrwcephalus lotus) 
 
 412, 686 
 
 ,, acanthotrias, definition of, 561 
 
 ,, bacillaris, .- . . 324 
 
 . , nut inn, . . . . 667 
 
 capensis, .... 398 
 ,, cvenurus, duration of vitality of 
 
 eggs of, . . 337 
 Effects of, . . 566 
 Experiments with, 85 
 
 Hexamerous symmetry 
 
 in, . . . 396 
 Host of, . . 405 
 Infection of cattle by, 65 
 Polycephaly of, . 404 
 Rostellum of, . 401 
 Sexual organs of, . 306 
 Slow development of, 123 
 Wandering of embryos 
 
 of, ... 70 
 
 ctassiceps, . . . 356, 405 
 crassicollis, developed from Cysti- 
 
 cercus fasciolaris, 405 
 ,, Embryos found in 
 
 portal vein, . 339 
 , , Energetic movements 
 
 of, . . . 425 
 Hooks of, . 392, 524 
 ,, Important conclusion 
 
 suggested by, . 36 
 
 Life-history of, . 80 
 
 ,, Limited to one host, 12 
 
 141 Malformations of, 39,6399 
 
 686 ., .. Receptacle of, . 355 
 
 Rostellum of, . 401 
 11 ,, ,, T. echinococcus mis- 
 
 37 taken for, . 591 
 
 273, 385 ,, crasslrostris, . . . 363 
 47 ,, craterifvrmis, . . . 322 
 critica, .... 280 
 rucumcrina, case of, in dog, 143 
 
 143,163 Cysticercoid of, 653 
 
 12,46 ,, Definition of, . 665 
 
 , 47 ,, ,, Double genital open- 
 
 47, 143 ings in, . . 279 
 
 143 ,, ,, Effects of, . 141 
 
 47,143 Eggs of, in dog-louse, 81 
 
 11 , , Life-history of, . 669 
 
 , 66, 130 f , Occurrence in man, 389 
 
 192 , , Relation of to Scoleces, 373 
 
 143 , , Simple rostellum of, 393 
 
 351 , , supposed adults of 
 
 588 . T. echinococcus, 591 
 
GENERAL INDEX. 
 
 765 
 
 PAGE 
 
 Tcenia cucurbitina, . . . 415 
 ,, grandis saginata, 406, 416 
 
 ,, dentata, . . . . 418 
 ,, denticulata, . . . 317, 398 
 dispar, .... 330 
 ,, cchinococcus, copulation of, . 310 
 ,, ,, Definition of, . 586 
 
 , , Distribution of blad- 
 
 der-worm, . 632 
 ,, Effects of the adult 
 
 worm, . 141 
 ,, ,, of the bladder- 
 
 worm, . 643 
 Eggs of, . . 590 
 ,, ,, Excretory organs of, 
 
 588, 604 
 ,, ,, Generative organs 
 
 of, . . 589 
 
 ,, ,, Growth of, . 591 
 
 Head of, . 506, 603 
 
 Hooks of, . 587, 604 
 
 ,, ,, ,, Variations in, 384 
 
 ,, ,, Megnin's theory of 
 
 life-history of, 403 
 ,, ,, Situation of, . 590 
 
 ,, ,, Suckers of, . 588 
 
 ,, ,, Supposed occurrence 
 
 in man, . 593 
 ,, ,, Supposed origin of, 
 
 from intestinal 
 villi, . . 591 
 ,, elliptica, See T. cucumerina. 
 expansa, . 279, 324, 398, 655 
 
 ,, fenestrata, .... 457 
 ,, fiavo-punctata, . 389, 390, 661 
 Giardi, 
 
 Tcenia nana, confounded with T. echino- 
 
 coccus, . . 154, 592 
 
 ,, Definition of, . . 657 
 
 ,, Development of, . 659 
 
 Occurrence in man, . 389 
 
 ,, nilotica, .... 366 
 
 ,, nymphcea, .... 55 
 
 ,, ocellata, .... 309 
 
 ,, pectinata, .... 403 
 
 , , perfoliata, adult of T. plicata, 383, 744 
 
 ,, Cirrhusof, . . 310 
 ,, ,, Large number in a 
 
 horse, . . 11 
 ,, ,, Megnin's view regarding, 
 
 403 
 
 , , , , Position of male aper- 
 ture in, . . 309 
 ,, ,, Sterile joints of, . 383 
 ,, pistillum, .... 363 
 ,, plana peUucida, . . . 416 
 ,, plicata, wandering of, . 139 
 ,, Young of T. perfoliata, 
 
 383, 744 
 
 ,, polyacantha, . . . 405 
 ,, prima Plateri, . . . 686 
 ,, saginata, bladder-worm of, . 458 
 , , Conditions affecting in- 
 fection by. . 481 
 ,, Definition of, . 406 
 ,, Developed from Cysti- 
 
 cercus bovis, . 405 
 
 ,, Diagnosis of eggs of, 145 
 
 ,, ., Distribution of, . 476 
 
 ,, Epidemic of, . . 168 
 ,, Experimental rearing 
 
 
 ,, Generative organs of 
 
 , grisea, . . . 686, 733 
 
 female, . 441 
 
 , infundibuliformis, . . 384 
 
 ,, male. . 438 
 
 , intermedia, . . . 405 
 
 ,, ,, Their development, 431 
 
 , Krabbei, . . . 405, 498 
 
 Growth of, . 423,428 
 
 , lanceolata, . . . 163, 384 
 
 ,, ,, Historical account of, 408 
 
 , lata, . . 477, 686, 733, 741 
 
 , , Infection of cattle by, 65 
 
 , litterata, . . . 278, 325 
 
 ,, Malformations of, . 449 
 
 , lophosoma, . . . 398, 453 
 
 ,, Mummy of , . . 485 
 
 , macropeos, .... 364 
 
 Muscles of, . . 293 
 
 , madagascariensis, . 389, 390, 663 
 
 ,, Name proposed, . 421 
 
 , marginata, definition of, . 563 
 
 Proglottides of, . 423 
 
 , developed from Cysti- 
 
 ,, ,, Sexual Development of, 445 
 
 cercus tenuicollis, 405 
 
 ,, Situation of, . 485 
 
 ,, Hooks of, . . 567 
 
 ,, Uterus of, . . 425 
 
 ,, , Infection of cattle by, 65 
 
 ,, Weinland on, . 422 
 
 ,, , Lamb fed with, 133, 339 
 
 , ,, var. abietina, . 479 
 
 , , , Life-history of, . 80 
 
 , sans e"pine (= T. saginata), . 412 
 
 ,, , Processes of egg of, 325 
 
 , scutigera, .... 363 
 
 ,, , Wandering of em- 
 
 , secunda Plateri, . . . 686 
 
 bryos of, . 70 
 ,, mediocanettata, . , . 420 
 
 , serrata, appendage of eggs of, 325 
 , ,, Developed from Cysti- 
 
 (See T. saginata.) 
 
 cercus pisiformis, . 405 
 
 ,, mcmbranacca, confounded with 
 
 , Differential diagnosis of, 566 
 
 Bothrioccphalus latus, . 733 
 
 , Effects of, on liver, . 135 
 
 (See also T. grisea. ) 
 
 ,, Erroneously diagnosed, 496 
 
 ,, microsoma, . . . 363 
 
 , , Ex periment on rabbit with, 1 5 3 
 
 ,, moniliformis, . . . 667 
 
 Hooks of, . . 524 
 
 ,, multiplex, .... 356 
 
 ,, Infection of cattle by, 65 
 
766 
 
 GENERAL INDEX. 
 
 Tcenia serrate, Me'gnin's theory regard 
 
 ing, ... 403 
 ,, ,, Rate of development of, 
 
 339, 383 
 
 Rostellum of, . . 401 
 T. echinococcus confounded 
 
 with, ... 591 
 Viability of eggs of, . 337 
 Wandering of embryos of, 70 
 set gera, . . 307, 341, 661 
 sol um, Co-existence of tape-worm 
 
 with bladder- worm, 546 
 Definition of, . . 488 
 Development of, . 498 
 Diagnosis of eggs of, 145 
 
 Distribution of, . 529 
 Generative organs of, 525 
 Growth of, . . 514 
 Head of, ... 520 
 Hooks of, . . 523 
 
 Infection by, . . 531 
 Malformations of, . 518 
 Pathological effects of, 535 
 Proglottides of, . 519 
 
 Self-infection by, . 153 
 Uterus of, . . 519 
 Viability of eggs of, . 337 
 Wandering of adult, . 139 
 
 tcnclla, 
 
 tenuicoUis, 
 
 torulosa, 
 
 uncinata, 
 
 undulata, 
 
 unilateralis, 
 
 vertebrate, 
 
 villosa, 
 
 visceralis, 
 
 vulgaris, 
 Tseniadse, asserted 
 ment of, 
 
 415, 498, C86, 733 
 405 
 
 365, 653 
 312 
 
 394,401,402 
 364 
 
 ... 686 
 
 10 
 
 353 
 
 415, 419, 692, 733, 741 
 direct develop- 
 
 403 
 
 ,, Definition of, . . 391 
 
 ,, Relations and characters of, 388 
 
 Synopsis of, ... 390 
 
 Taniarhynchus, . . . 390, 406 
 
 Tape and bladder worms, co-existence 
 
 of, 546 
 
 Temperature, effect of, on Entozoa, 75 
 
 Tench, parasite of, . . . 654 
 
 Tenebrio, 661 
 
 ,, molitor, . . . .65, 331 
 
 Teniens 388 
 
 Testes of Bothriocephalus lotus, . 699 
 ,, of Tcenia echinococcus, . 589 
 
 ,, of ,, saginata, . . 438 
 
 Tethys, 371 
 
 Tetrabothrium auricula, . . 310 
 
 TetraphyUes, .... 388 
 
 Tetrarhynchus, cuticular cyst of, . 20 
 
 Cysticercus-Bi&ge of, 369 
 Definition of, . . 388 
 Formation of the head of, 375 
 Wandering of heads of, 371 
 lingualis, . . 380 
 macrobothrius, . 371 
 sepice, . . . 371 
 
 PAOR 
 
 Thetis, blood corpuscles of, . . 178 
 Totanus calidris, .... 361 
 Transmission of parasites effected in 
 
 young stage, . . . . 155 
 Trematodes, affinity of, to Cestodes, 105 
 ,, Anenteric, . . 106 
 
 ,, Derived from Planarians, 107 
 
 Tricenophorus, . . . . 56, 377 
 Trichina spiralis, analogy to Filar ia, 51 
 Calcareous cyst of, 20 
 
 Effects of, . . 126 
 History of knowledge of, 40 
 Irritation due to, 141 
 
 not developed in birds, 85 
 Occurrence in Nema- 
 
 todes, . . 11 
 
 the only case of com- 
 plete parasitism, 103 
 Result of experiments 
 
 with, . . 124 
 Sketch of life-history of, 90 
 Various hosts of, . 12, 159 
 Wandering of, . 340 
 6, 56, 90 
 154 
 
 146, 154 
 81 
 669 
 246 
 
 Trichoccphalus, 
 
 ,, crenatus, 
 
 ,, dispar, . 
 
 Trichodectes, 
 
 ,, canis, 
 
 Trichomonas, Definition of, 
 
 batrachorum, 239, 240, 247 
 caudata, . . . 252 
 elongata, . . . 252 
 flageUata, ... 252 
 intestinali*, definition of, 250 
 ,, Distinctness of, 243 
 limacis, . . . 246 
 vaginalis, definition of, 248 
 ,, Discovery of, . 246 
 ,, Resemblance to 
 
 Tcenia intestinalis 251 
 Trichosomum, Worm-nests of, . 48 
 
 ,, cratncavda, parasitic 
 
 male of, . . 10 
 
 Tricuspidaria, parasites of, . . 388 
 Turbellaria, parasites of, . . 117 
 
 Udonetta, . . . . . * . 107 
 
 Umbilical worms, . , . . 121 
 
 Urospora nemertidis, * . . . 194 
 
 Uterine opening, .... 308 
 
 Uterus of Bothriocephalus latus, . 701 
 
 of Cestodes, . . . 316 
 
 of Tcenia ccenurus, . . 568 
 
 of ,, marginata, . . 568 
 of ,, saginata, . 425, 445 
 
 of ,, serrata, . . 568 
 
 of ,, solium, . . 519 
 
 Vagina of Tcenia echinococcus, . 589 
 
 of ,, saginata, . . 442 
 
 Vaginiferae . 307 
 
 Vascular system, development of, . 348 
 
 Vermes, definition of, . . . 265 
 
 ,, Subdivisions of, . . 267 
 
 ,, cucumcrini, . 424 
 
GENERAL INDEX. 
 
 767 
 
 Verities, cucurbitini, 
 
 Verminatio, . 
 
 Vesicaria lucii, 
 
 Vorticella, . 
 
 Vibriones, 
 
 Villot on Gordius, 
 
 272 
 122 
 
 . . 377 
 
 231, 235, 253 
 
 241, 244 
 
 . 35, 63 
 
 Virchow on Trichina spiralis, . 40 
 
 Vix on conditions of development in 
 
 Nematodes, . . . 54 
 
 on Oxyuris, . . . . 56, 147 
 
 Walrus, parasite of, ... 13 
 
 Wandering in the brain and liver, . 70 
 
 ,, of adult parasites, . 138 
 
 ,, of heads of Tetrarhynchus, 371 
 
 of parasites, . . 67, 132 
 
 I'AGE 
 
 Wandering of parasites, effects of, 140 
 
 Means of, 138 
 
 ,, of tape- worms, . 139 
 
 Weiuland on reproduction of corals 81 
 
 Wolf, parasite of, . . . 80 
 
 Worm-abscesses, ... 138 
 
 Worm-aneurism of horse, . 74, 131 
 
 Worm-fever, ... 122 
 
 Worm-irritation, ... 122 
 
 Worm-knots, . , . ^ 47 
 
 Worm-nests, ... 47 
 
 confined to Nematodes, 48 
 
 Zeller on Distomum, macrostomum, . 72 
 
 on Polystomum integerrimum, 40 
 
 Ziirn on influenza of rabbits, . 227 
 
 [INDEX OF AUTHORITIES. 
 
LIST OF AUTHORITIES. 
 
 
 1>AOR 
 
 32 
 
 Carswell, . 
 
 PAGE 
 
 .' . . 204 
 
 Aetius . 
 
 409 
 
 Carter, . 
 
 164 
 
 Aitken, .... 
 
 137 
 
 Charoot, 
 
 585 
 
 Andry, .... 
 Aristotle, .... 
 
 120 
 148 
 
 Cienkowsky, . 
 Oaparede, 
 
 185 
 228, 282, 372 
 
 Aubert, .... 
 
 70, 364 
 
 Glaus, . . 
 
 . 43, 93, 95 
 
 
 185 
 
 Cloquet, 
 
 511 
 
 
 
 Clot, 
 
 . . 168 
 
 Baer, von, .... 
 Baillet, 
 Balbiani 
 Barker 
 
 30, 139 
 85, 566 
 196, 232 
 631 
 
 Cobbold, 
 
 Cohn, . 
 Colin, . 
 
 . 50, 453, 467, 472, 
 484, 532, 640, 745 
 180, 181 
 450 
 
 
 651 
 
 Coulet, 
 
 271 
 
 
 643 
 
 Creplin, 
 
 33, 732 
 
 
 109 
 
 Cruse, . 
 
 152 
 
 Barv De 
 
 185 
 
 Cruveilhier, . 
 
 643, 650 
 
 
 94 
 
 Cullingworth, 
 
 453 
 
 Batsch, .... 
 
 416 
 
 
 186 
 
 Belfrage, .... 
 
 267 
 
 
 
 Bendz, .... 
 Beneden, Ed. van, 194, 323, 
 Beneden, P. J. van, 11, 38, 75, 
 272, 273, 317, 
 336, 349, 372, 
 421, 
 
 356, 357 
 325, 468 
 124, 
 335, 
 388, 
 491, 507 
 
 Daoonta, 
 Dallinger, . 
 Darbon, 
 Davaine, . 
 
 Delafond, . 
 
 152 
 . ' . 237 
 
 487 
 27, 53, 54, 191, 237, 
 242, 580, 585, 612, 617 
 49, 238 
 
 
 298 
 
 |\; 
 
 o<77 71 c 7.10 
 
 Berlin, 
 
 558 
 
 Diesing, 
 
 oil, /ID, rW 
 
 Berthold, .... 
 Bertolus, .... 
 Bilharz, .... 
 
 . 3, 651 
 496, 714 
 476, 657 
 
 Dim mock, 
 Doeveren, van, 
 Donnadieu, . 
 
 . 44 
 
 . . . 27 
 317, 378 
 248 
 
 Birch-Hirschneld, . 
 
 545 
 
 Dressel, 
 
 541 
 
 Bloch, 
 
 10 
 
 Drysdale, . 
 
 237 
 
 Blocbmann, .... 
 Blumberg, .... 
 
 247, 248 
 296, 307 
 632 
 
 Duchamp, . 
 Dujardin, 
 
 379 
 . . 9, 36, 228, 330 
 
 Boerhaave, .... 
 p^-ii- 1 90 i ai 
 
 24 
 
 ae)A 7Qft 
 
 Eberhard 
 
 27 
 
 Bonetus, .... 
 
 556 
 
 KAA 
 
 Ebert, . 
 Eberth, . 
 
 94 
 
 198 
 
 Bonnet, .... 
 Borrell, .... 
 
 413, 414 
 52 
 
 Ecker, . 
 Ehrenberg, . 
 
 47 
 . . 177 
 
 Botticher, . . 134, 296, 
 
 303, 683 
 
 KAfi 
 
 Eimer, . 
 Eisig. 
 
 198 
 140 
 
 Brass, 
 
 189 
 
 Ekeckrantz, . 
 
 242 
 
 Braun, ..... 
 "RrPiriBpr 9R 199 S'ifi 
 
 159 
 ^70 4^7 
 
 Engelmann, . 
 
 262 
 
 4 52, 98 
 
 Brera, 
 Buchholz, . .. ," ~ 
 
 29, 511 
 93 
 47 
 
 Eschricht, . 
 
 . 32, 280, 336, 666, 578 
 512 
 
 Burdach, .... 
 
 30 
 
 Feuereisen, . 
 
 306 
 
 Busch, . 
 
 137 
 
 Fiedler, 
 
 .... 85 
 
 Butechli, 102, 228, 229, 235, 
 
 237, 344 
 
 Filippi, De . 
 
 39 
 
LIST OF AUTHORITIES. 
 
 769 
 
 
 PAGE 
 
 593, 632 
 
 Klebs, . 
 
 PAGK 
 
 181, 205, 547 
 
 Finck, 
 Fleming, 
 Fol, . 
 
 224 
 472 
 235 
 638 
 
 Kleefeld, 
 Klein, . 
 Klenke, 
 Kloss, . 
 
 535 
 181 
 38 
 197 
 
 
 162 
 
 Knaffl, . 
 
 618 
 
 
 301, 589 
 
 Knoch, 
 
 159 227 303, 471, 691, 714 
 
 Frantzius, von, 
 Friedberger, 
 Friedreich, . . ~ . 
 Flirstenberg, , , 
 
 Geddes, 
 
 161, 192 
 168 
 134, 626 
 157, 340 
 
 235 
 
 Knox, . 
 Koberld, 
 Koch, . 
 Kolliker, 
 Koplin, 
 Kossman, 
 
 168 
 556 
 180-181 
 248, 329, 714 
 565 
 ; . . 18 
 
 
 . , 337, 467 
 
 Kowalewsky, 
 
 . . 10 
 
 Giard, .... 
 
 117 
 
 Krabbe, 
 
 . 151-152, 384, 497, 
 
 
 418 
 
 
 530, 565, 638, 730 
 
 Goze, .... 
 
 . - 10, 512 
 
 Kramer, 
 
 668 
 
 Graefe and Saeniisch, . 
 
 542 
 
 Krause, . 
 
 11, 518 
 
 Graefe, von, . 
 Grassi, . 126, 160, 186, 
 Greeff, .... 
 Gribbohm, 
 Griesinger, . j. 
 Gruber, . . . 
 Gruby, . ,. 
 Gubain, 
 
 148, 542 
 189, 221, 733-741 
 111 
 123 
 . ' 127 
 365 
 . 49, 135, 238 
 545 
 
 Krohn, 
 Kliclienmeis ter 
 
 Kuhn, . 
 Lachmann, . 
 
 109 
 , 38, 39, 48, 82, 157, 
 330, 331-332, 335-336, 
 406, 497, 543, 544, 
 557, 559, 563, 583 
 157, 585 
 
 228 
 
 Gubler, ., . 
 Guillebeau, . 
 
 Hake, 
 Hammer, . 
 
 . 47, 222 
 . . 471 
 
 .- ~ . 204 
 
 643 
 
 Lambl, 
 Lancereaux, . 
 Landois, 
 L.ang, 
 Lankester, 
 
 145, 184, 242, 244 
 532 
 . , . 279, 296, 688 
 205 
 181 
 
 
 624 
 
 Lavalette, 
 
 486 
 
 Harting, 
 Hartmann, . 
 Hassall, . 
 Haubner, . . -.- 
 Hausmann, . 
 Heller, .... 
 Helm, . 
 
 284 
 84, 511 
 241 
 . 39, 157 
 248 
 84, 330 
 611 
 
 Leeuwenhoek, 
 Leidy, . 
 Leisering, 
 Lewin, . 
 Leske, . 
 Lessing, 
 Leuckart F S 
 
 253 
 . 49, 450, 661 
 133, 143, 157, 594 
 . 510 
 557, 584 
 544 
 . . 91 370 388 
 
 Henle, .... 
 Hennig, . . . 
 Henschen, 
 Henschl, . ; 
 Hering, .( 
 Hertwig, 
 
 47 
 248 
 257 
 127 
 144, 671 
 235 
 
 B., 
 
 Levacher, 
 Levi, 
 Levison, 
 
 2, 39-41, 51, 70, 81, 98, 
 17, 199, 274, 282, 333, 
 336, 355, 403, 421-422, 716 
 453 
 482 
 614 
 
 Herz, .... 
 
 486 
 200 
 
 Lewald, 
 Lewis, . 
 
 332 
 
 47 50 472 
 
 Heyfelder, 
 
 643 
 
 638 
 
 Leydig, 
 Lieberktihn, 
 
 67 
 
 178 193 194 195 213 
 
 Hoek, .... 
 
 370 
 
 Lindemann, . 
 
 226 
 
 Hoeven, van der, .- 
 Hoffmann, 
 
 333 
 
 ... 24 
 301 
 
 Linne, . 
 Linstow, von, 
 Losch, 
 
 . 25, 272, 667 
 . 11, 306, 363 
 186 
 
 Hollenbach, . 
 Huber, . 
 
 496 
 134, 459, 624, 731 
 
 Lubbock, 
 Liicke, . 
 
 116 
 
 . . . 630 
 
 Huss, . 
 Huxley, 
 
 Jordens, 
 
 729 
 109, 578 
 
 121 
 
 Ludersen, 
 Luschka, 
 
 Maan de 
 
 632 
 ~ . . . 626 
 
 94 
 
 Kahane, ... 
 Kaschin, 
 Kauffmann, . 
 Kiessling, 
 Kjellberg, . 
 
 279 
 478 
 203 
 748 
 221 
 
 Mackenzie, 
 Mackenzie, . 
 Maddox, 
 Magalhaes, . 
 Malmsten, 
 Malpighi, 
 
 50 
 551 
 498 
 57 
 254 
 511 
 
 3 C 
 
770 
 
 LIST OF AUTIIOKITIES. 
 
 Manson, . . . .50, 64, 745 
 
 Marchand, 84, 250 
 
 Marion, . . . . . 94 
 
 Masars de Cazeles, . . . 457 
 Masse, ...... 475 
 
 Megnin, . . ' . 357, 384, 403 
 
 Mehlis, 
 
 Meissner, 63 
 
 Melnikoff, 81 
 
 Menz, 200 
 
 Mereschowsky, von, . . . 189 
 
 Meschede, 143 
 
 Metschnikoff, , 117, 178, 329, 366 
 Michelson, . . . . . 155 
 Miescher, . . . . 200 
 
 Minot, . . . . . 269 
 
 Moebiup, 475 
 
 Moniez, . 279, 317, 323, 330, 355, 
 
 398, 403, 688 
 
 Morin, 615 
 
 Mosler, . . . 133, 539, 735 
 
 Miiller, Fr. 93 
 
 Job. ... 91, 578 
 
 K 151 
 
 O. F. 26 
 
 Nasse, . 
 
 Nathusius, . 
 
 Naunyn, 
 
 Neisser, 
 
 Newport, 
 
 Nicolai, 
 
 Niemiec, 
 
 Nitsche, 
 
 Nitzsch, 
 
 Nordmann, von, 
 
 Normand, 
 
 Numan, 
 
 Oertel, . 
 O'Neill, 
 Onymus, 
 
 204 
 11 
 
 593, 594, 631 
 
 632 
 
 61 
 
 419 
 
 395 
 
 296, 401 
 
 91, 369 
 
 30, 550 
 
 125 
 
 129 
 
 181 
 145 
 545 
 
 Pagenstecher, 
 Pallas, . 
 Panceri, 
 Parona, . 
 
 Paulicki, 
 Pellizzari, 
 Perls, . 
 Perona, . 
 
 ), 111, 280, 282, 306, 614 
 
 . 26, 84, 333, 584 
 
 372 
 
 661, 730 
 228 
 532 
 558 
 126, 160 
 
 Perroncito, . 157, 469, 482, 533, 624, 730 
 
 Petersson, 257 
 
 Pintner, 296 
 
 Piorry, 612 
 
 Plater, ; 410, 565 
 
 Platner, . 338 
 
 Pourquier, 475 
 
 Probstmayr, 475 
 
 Prougeansky, .... 626 
 Pruner, .... 485 
 
 Rainey, 
 
 Ransom, 
 
 Rasniussen, 
 
 200 
 656 
 603 
 
 Rathke, 
 Ratzel, . 
 Raum, . 
 Redi, . 
 Redon, 
 Reichenbach, 
 Reincke, 
 Remak, 
 Rendtorff, von, 
 Richardson, . 
 Riehm, 
 Rindfleisch, . 
 
 PAGE 
 
 67 
 363 
 133 
 
 23 
 510 
 178 
 203 
 204 
 632 
 639 
 301 
 283 
 
 Rivolta, . 52, 144, 203, 215, 225, 227 
 
 Robin, 486 
 
 Rokitansky, . . . . 542 
 
 Roloff, . . . . 205, 207 
 
 Rosenstein, 157 
 
 Rudolphi, . 388, 458 
 
 Rupprecht, . . . .. . 157 
 
 Ruschhaupt, . . . .194 
 
 Russell, . . . . . 618 
 
 Russworm-Gleichen, von, . . 230 
 Ruyssenaere, . . . . 626 
 
 Salensky, . . . . . 329 
 Salzmann, . . . . 668 
 
 Sappey, 498 
 
 Sara, . . . . _ . . 273 
 
 Scanzoni, . ." " . i 248 
 S< -1 Kin ii island, . . . 714 
 
 Scheube, 51 
 
 Schiefferdecker, . . . . 279 
 
 Schleissner, . . . . 151, 637 
 
 Schmidt, A. . . . , . 194 
 
 Schmidt, von, ... . . . 227 
 
 SchmidtmUller, . . . . 418 
 
 Schneider, Aimd, . 192, 193, 196, 
 
 198, 202 
 Schneider, Anton, 94, 95, 111, 269, 289 
 
 Schott, 550 
 
 Schultze, F. E. . . . . 189 
 Schultze, Max, . . . 109, 178 
 
 Siebert 547 
 
 Siebold, von, 30, 34, 35, 36, 37, 48, 63, 
 72, 82, 175, 200, 272, 322, 
 
 332, 333, 334, 356, 657 
 Siedamgrotzky, . . . . 471 
 Silvestrini, . . . . . 227 
 
 Simonds, 467 
 
 Sograff, 677 
 
 Sommer, . 144, 279, 296, 305, 423, 688 
 Sommerbroat, . . . . 616 
 Sommering, . . .' - . . 550 
 Spengel, . . . . 15 
 
 Spooner, . . . .. 658 
 
 Steenstrup, 25, 33 
 
 Stein, . . . 192, 228, 237, 253, 331 
 Steinberg, ..... 241 
 
 Steinbuch 508 
 
 Steudener, . . . . 279, 393 
 
 Stich, .... 501, 536, 544 
 
 Stieda, . . 203, 256, 306, 307, 687 
 
 Stirling, . . ... . 47 
 
 Swammerdam, .... 23 
 
 Szydlowksi, 730 
 
LIST OF AUTHORITIES. 
 
 771 
 
 
 PAGE 
 
 472 
 
 Wawruch, 
 
 PAGE 
 
 418, 481 
 
 Thaddseus, Dunus, 
 Tham, . 
 
 410 
 242 
 168, 592 
 
 Wecker, De, 
 Wedl, . 
 Weijenberg, . 
 
 546 
 137, 241 
 144 
 
 Thorstensen, 
 Treitte, 
 Treutler, 
 
 151 
 
 257 
 497 
 
 Weinland, 
 Weisse, 
 Welch, .... 
 
 82, 137, 422, 561 
 459 
 450 
 
 Tschudi, 
 
 400 
 
 Wendt, 
 
 545 
 
 Tyson, . . 
 
 413 
 
 Wepfer, 
 
 557 
 
 Valentin, 
 
 . . . 33 
 
 Werner, 
 Westphal, 
 
 413 
 660 
 
 Valette, 
 Vallisnieri, . . 
 
 39 
 26, 271, 412 
 
 Willemoes-Suhm, von, 
 Windbladh, . 
 
 . ' 57 
 257 
 
 
 ... 10 
 
 
 254 
 
 
 714 
 
 Wrze'sniowski, 
 
 231 
 
 Vernet, , . 
 
 ' /: . . . 98 
 
 
 160 
 
 Villot, . . ...-'. 
 Virchow, . . 
 Vix, . 
 
 . 35, 73, 363 
 . 40, 201, 586, 614 
 56 
 
 Wunderlich, . 
 Zaeslin, . . . 
 
 616 
 729 
 
 Vogel, . 
 
 253 
 
 Zeder, . 
 
 377 
 
 Vogt, . 
 Wagener, 
 
 49, 732 
 295, 301, 334 
 
 Zeller, . 20, 40, 72, 
 Zenker, 
 Zopf, 
 
 164, 262, 625, 626 
 . 48, 468, 554 
 185 
 
 Wagner, 
 Walch, 
 Waldenburg, 
 
 40, 578 
 49 
 . 20, 128, 185, 211 
 
 Zulzer, . 
 Zunker, 
 Ziirn, . . 
 
 510 
 242 
 227, 468, 538 
 
 E R K A T A. 
 
 Page 37, explanation of Fig. 24, for " EcMnobothrium " read " Eckeneibothrium." 
 
 Page 140, line 11 from below, for " conjunction " read " conjunctiva." 
 
 Page 377, line 9 from below, for " Spargarum " read " Sparganum." 
 
 Page 388, line 7 from below, after " Tetrarhynchi " insert a parenthesis. 
 
 Page 568, line 7, for " structure " read "uterus." 
 
 Page 490, line 22, for "of the Bladder-worm" read " from the Bladder- worm. " 
 
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 publication of original contributions to General Pathology, Patho- 
 logical Anatomy, and Experimental Pathology, including 
 Bacteriology. These articles will, of course, be mainly from 
 British Laboratories and Hospitals ; but the co-operation of many 
 distinguished Continental, American, and Colonial Pathologists has 
 been obtained, and papers written or edited by them will be placed 
 before our readers. 
 
 In order to increase the interest and extend the usefulness of the 
 Journal, it is intended that, in addition to original articles, critical 
 summaries of work done in special departments of Pathology and 
 Bacteriology shall from time to time be published. All articles 
 appearing in the Journal will be signed. 
 
 The Journal appears at least four times a year, but it will be 
 issued more frequently if necessary, in order to ensure publication 
 of all papers as early as possible after they are received. 
 
 The numbers issued throughout the year form a volume, royal 8vo, 
 of about 500 pages. They are printed on good paper, and freely 
 illustrated with Chromo-lithographs and figures in black and 
 white. 
 
 Amongst those who collaborate are the following : J. G. Adami, 
 Montreal ; S. Arloing, Lyons ; B. Bang, Copenhagen ; Ch. 
 Bouchard, Paris ; R. Boyce, Liverpool ; J. Rose Bradford, 
 London ; H. Buchner, Munich ; Sir Charles Cameron, Dublin ; 
 Angelo Celli, Rome ; A. Chantemesse, Paris ; A. B. Charrin, 
 Paris ; A. Chauveau, Paris ; W. Watson Cheyne, London ; 
 H. Chiari, Prague; W. T. Councilman, Boston; S. Del^pine, 
 Manchester; J. Dreschfeld, Manchester; D. Drummond, New- 
 castle ; Von Esmarch, Koenigsberg ; Ch. Firket, Liege ; R. H. 
 Fitz, Boston ; P. Grawitz, Greifswald ; W. S. Greenfield, Edinburgh ; 
 E. H. Hankin, Agra ; Victor Horsley, London ; F. Hueppe, 
 Prague ; O. Israel, Berlin ; R. F. C. Leith, Birmingham ; Alfred 
 Lingard, Poonah ; Lord Lister, London ; P. Marie, Paris ; E. 
 Metchnikoff, Paris ; F. W. Mott, London ; Robert Muir, Glasgow ; 
 E. Nocard, Alfort ; T. Oliver, Newcastle; J. Orth, Got- 
 tingen ; William Osier, Baltimore ; J. F. Payne, London ; 
 T. Mitchell Prudden, New York ; J. M. Purser, Dublin ; C. J. 
 Salomonsen, Copenhagen ; Sir J. Burdon Sanderson, Oxford ; C. S. 
 Sherrington, Liverpool ; J. Lorrain Smith, Belfast ; A. M. Stalker, 
 Dundee; H. Stilling, Lausanne; I. Straus, Paris; T. P. Ander- 
 son Stuart, Sydney ; R. Thoma, Dorpat ; E. Trevelyan, Leeds ; 
 Sir John Batty Tuke, Edinburgh; L. Vaillard, Paris; Rudolf 
 Virchow, Berlin ; H. Marshall Ward, Cambridge ; A. Weich- 
 selbaum, Vienna; C. Weigert, Frankfort a/M ; W. H. Welch, 
 Baltimore; Sir Samuel Wilks, Bart., London; A. E. Wright, 
 Netley ; Von Zenker, Erlangen ; E. Ziegler, Freiburg. 
 
ISSUED BY YOUNG J. PENTLAND. 15 
 
 Keating, John M., M.D., LL.D., 
 
 Fellow of the College of Physicians of Philadelphia ; late Visiting Obstetrician to the 
 Philadelphia Hospital, and Lecturer on Diseases of Women and Children, Phila- 
 delphia Hospital. 
 
 A NEW PRONOUNCING DICTIONARY OF MEDICAL 
 TERMS. New Impression. Large 8vo, cloth, pp. 818. Price 
 7s. 6d. nett. 
 
 Keating, John M., M.D., LL.D., 
 
 and 
 
 Coe, Henry C., M.D., M.R.C.S., 
 
 Professor of Gynaecology, New York Polyclinic. 
 
 CLINICAL GYNAECOLOGY, MEDICAL AND SURGICAL. 
 
 By American Teachers. 2 vols., royal 8vo, cloth extra, gilt tops, 
 pp. xviii., 994. Illustrated with 34 full-page plates and 377 
 engravings in the text. Price 25s. nett. 
 
 Keith, Skene, F.R.C.S.Ed., 
 
 GYNAECOLOGICAL OPERATIONS, EXCLUSIVE OF THOSE 
 INTERFERING WITH THE PERITONEAL CAVITY. 
 8vo, cloth extra, pp. xii., 118. Illustrated with 44 figures. Price 
 5s. nett. 
 
 Keith, Skene, F.R.C.S.Ed., 
 
 Assisted by 
 
 Keith, George E., M.B., C.M. 
 
 TEXT-BOOK OF ABDOMINAL SURGERY. A Clinical Manual 
 for Practitioners and Students. 8vo, cloth, gilt top, pp. xvi., 508. 
 With 34 illustrations. Price 16s. (PentlancTs Medical Series, 
 Volume Fourth.} 
 
 Kelynack, T. N., M.D.(VicL), M.R.C.P.(Lond.), 
 
 Pathologist, Manchester Royal Infirmary; Demonstrator and Assistant Lecturer in 
 Pathology, Owens College, Manchester. 
 
 RENAL GROWTHS: THEIR PATHOLOGY, DIAGNOSIS, 
 AND TREATMENT. 8vo, cloth, pp. xvi., 269. With 96 illus- 
 trations. Price 12s. 6d. nett. 
 
16 CATALOGUE OF MEDICAL PUBLICATIONS 
 
 Lanclis, Henry Q., A.M., M.D., 
 
 Late Professor of Obstetrics and Diseases of Women in Starling Medical College. 
 
 COMPEND OF OBSTETRICS. Fourth Edition, thoroughly re- 
 vised, enlarged, and improved. Crown 8vo, cloth, pp. 118, with 
 1 7 illustrations. Price 4s. 6d. 
 
 Leuckart, Rudolf, 
 
 Late Professor of Zoology and Comparative Anatomy in the University of Leipsic. 
 
 THE PARASITES OF MAN AND THE DISEASES WHICH 
 PROCEED FROM THEM. A Text-Book for Students and 
 Practitioners. Translated from the German with the co-operation 
 of the Author by WILLIAM E. HOYLE, M.A. (Oxon.), M.R.C.S., 
 F.R.S.E., Curator of the Museums, Owens College, Manchester. 
 Natural History of Parasites in General. Systematic Account 
 of the Parasites Infesting Man. PROTOZOA. CESTODA. Large 
 8vo, cloth, pp. xxviii., 772. Illustrated with 404 engravings. Price 
 31s. 6d. 
 
 geon to St. 
 d, London. 
 
 Lockwood, Charles Barrett, F.R.C.S., 
 
 Hunterian Professor, Royal College of Surgeons of England ; Assistant Surg< 
 Bartholomew's Hospital ; Surgeon to the Great Northern Central Hospital, 
 
 TRAUMATIC INFECTION. Hunterian Lectures delivered at the 
 Royal College of Surgeons of England. Crown 8vo, cloth, pp. xii., 
 138. Illustrated with 27 wood engravings in the text. Price 3s. 
 
 ASEPTIC SURGERY. Second Edition. Crown 8vo, cloth, pp. 
 xvi., 264. Price 4s. 
 
 THE RADICAL CURE OF HERNIA, HYDROCELE, AND 
 VARICOCELE. Crown 8vo, cloth, pp. xii., 279, with 23 illustra- 
 tions. Price 4s. 6d. 
 
 McBride, P., M.D., F.R.C.P.Ed., 
 
 Surgeon to the Ear and Throat Department of the Royal Infirmary ; Lecturer on 
 the Diseases of the Throat and Ear in the University, and in the School of 
 Medicine of the Royal Colleges, Edinburgh. 
 
 DISEASES OF THE THROAT, NOSE, AND EAR. A Clinical 
 Manual for Students and Practitioners. Third Edition, revised 
 and partly rewritten. 8vo, cloth, pp. xvi., 744, with 46 coloured 
 illustrations from original drawings. Price 25s. (Pent land's 
 Medical Series, Volume Third.) 
 
 Maguire, Robert, M.D., F.R.C.P., 
 
 Physician to, and Joint Lecturer on Pathology, St. Mary's Hospital ; Assistant 
 Physician, Consumption Hospital, Brompton, London. 
 
 THE INVOLUTION OF LIFE : A Scheme of Pathology. 8vo, 
 cloth, pp. 23. Price Is. 6d. nett. 
 
ISSUED BY YOUNG J. PENTLAND. 17 
 
 Mackenzie, James, M.B., 
 
 THE STUDY OF THE PULSE, ARTERIAL, VENOUS, AND 
 HEPATIC, AND OF THE MOVEMENTS OF THE HEART. 
 8vo, cloth, gilt top, pp. xx., 322. With many illustrations. Price 
 18s. 
 
 Maclaren, P. H., M.D., F.R.C.S.Ed., 
 
 Surgeon, Edinburgh Royal Infirmary ; formerly Surgeon in charge of the Lock 
 Wards, Edinburgh Royal Infirmary ; Examiner in the Royal College of Surgeons, 
 Edinburgh. 
 
 ATLAS OF VENEREAL DISEASES. A Series of Illustrations 
 from Original Paintings, with Descriptions of the Varied Lesions, 
 their Differential Diagnosis and Treatment. In 10 fasciculi, price 
 6s. each ; or complete in one handsome royal quarto volume, extra 
 cloth, price 63s. nett. 
 
 Martin, Sidney, M.D., F.R.S., F.R.C.P., 
 
 Physician, University College Hospital ; Professor of Pathology, University College, 
 London. 
 
 FUNCTIONAL AND ORGANIC DISEASES OF THE 
 STOMACH. 8vo, cloth, pp. xx., 506. Illustrated with 57 
 engravings throughout the text. Price 16s. (Pentland's Medical 
 Series, Volume Fifth.} 
 
 Mills, Charles K., M.D., 
 
 Professor ot Mental Diseases and of Medical Jurisprudence in the University of 
 Pennsylvania ; Clinical Professor of Neurology in the Women's Medical College, 
 Pennsylvania. 
 
 THE NERVOUS SYSTEM AND ITS DISEASES. A Practical 
 Treatise on Neurology for the Use of Physicians and Students. 
 Large 8vo, cloth, pp. xxx., 1056, with 459 illustrations. Price 25s. 
 
 THE NURSING AND CARE OF THE NERVOUS AND 
 THE INSANE. Crown 8vo, cloth, pp. 147. Price 4s. 6d. 
 
 Morison, Alexander, M.D., F.R.C.P.Ed., 
 M.R.C.P.Lond., 
 
 Physician in charge of Out-Patients to the Great Northern Central Hospital and 
 the Children's Hospital, Paddington Green ; Physician to the St. Marylebone 
 General Dispensary, London. 
 
 ON THE RELATION OF THE NERVOUS SYSTEM TO 
 DISEASE AND DISORDER IN THE VISCERA. Being 
 the Morison Lectures delivered before the Royal College of 
 Physicians in Edinburgh in 1897 and 1898. 8vo, cloth, gilt top, 
 pp. xvi., 132, with 39 illustrations. Price 7s. 6d. 
 
1 8 CATALOGUE OF MEDICAL PUBLICATIONS 
 
 Morrow, Prince A., M.D., 
 
 Clinical Professor of Geni to- Urinary Diseases ; formerly Lecturer on Dermatology in 
 the University of the City of New York ; Surgeon to Charity Hospital, New York. 
 
 SYSTEM OF GENITO-URINARY DISEASES, SYPHILOLOGY, 
 AND DERMATOLOGY. By VARIOUS AUTHORS. Edited by 
 PRINCE A. MORROW, M.D. In 6 divisional volumes of about 550 
 pages each. Royal 8vo, cloth extra, gilt tops, illustrated with 
 coloured plates and engravings throughout the text. Price per 
 volume, 14s. nett. Sold only by subscription. 
 
 Muir, Robert, M.A., M.D., F.R.C.P.Ed., 
 
 Professor of Pathology, University of Glasgow, 
 and 
 
 Ritchie, James, M.A., M.D., B.Sc., 
 
 Lecturer in Pathology, University of Oxford. 
 
 MANUAL OF BACTERIOLOGY. Third Edition, revised and 
 enlarged. Crown 8vo, with many illustrations. In Press. (Pent- 
 land 's Students' Manuals.} 
 
 Murray, R. Milne, M.B., F.R.C.P.Ed., 
 
 Assistant Physician, Royal Maternity and Simpson Memorial Hospital ; Lecturer on 
 Midwifery and Diseases of Women, School of Medicine, Edinburgh. 
 
 MANUAL OF MIDWIFERY. Crown 8vo, with numerous illus- 
 trations, pp. 500 or thereby. Preparing. 
 
 Muskett, Philip E., L.R.C.P. & S.Ed., 
 
 Late Surgeon to the Sydney Hospital ; formerly Senior Resident Medical Officer, 
 Sydney Hospital. 
 
 PRESCRIBING AND TREATMENT IN THE DISEASES OF 
 INFANTS AND CHILDREN. Third Edition, revised, enlarged, 
 and re-arranged. i8mo, pp. xx., 334, in flexible leather binding 
 for the pocket. Price 6s. 6d. 
 
 Musser, John H., M.D., 
 
 Assistant Professor of Clinical Medicine in the University of Pennsylvania ; Physician 
 to the Philadelphia and the Presbyterian Hospitals, etc. 
 
 PRACTICAL TREATISE ON MEDICAL DIAGNOSIS. For 
 
 Students and Physicians. Royal 8vo, cloth, pp. viii., 866. Illus- 
 trated with 162 engravings and 2 coloured plates. Price 24s. 
 
ISSUED BY YOUNG J. PENTLAND. 19 
 
 Newman, David, M.D., 
 
 Surgeon, Glasgow Royal Infirmary. 
 
 MALIGNANT DISEASE OF THE THROAT AND NOSE 
 8vo, cloth, pp. xii., 213, with 3 illustrations. Price 8s. 6d. 
 
 Norris, W. R, A.M., M.D., 
 
 Professor of Ophthalmology, University of Pennsylvania ; 
 and 
 
 Oliver, C. A., A.M., M.D., 
 
 Surgeon to the Wills Eye Hospital, Philadelphia. 
 
 TEXT-BOOK OF OPHTHALMOLOGY. Royal 8vo, cloth 
 pp. viii., 622. Illustrated with 5 coloured plates and 357 woodcuts 
 Price 25s. 
 
 Oliver, Thomas, M.D., F.R.C.P., 
 
 Physician, Royal Infirmary, Newcastle-on-Tyne ; Professor of Physiology, University 
 of Durham. 
 
 LEAD POISONING, IN ITS ACUTE AND CHRONIC 
 FORMS. 8vo, cloth, pp. xii., 122, with 32 illustrations, mostly in 
 colours. Price 10s. 6d. 
 
 Osier, William, M.D., LL.D., F.R.S., F.R.C.P., 
 
 Professor of Medicine in the Johns Hopkins University, and Physician-in-Chief to the 
 Johns Hopkins Hospital, Baltimore. 
 
 THE PRINCIPLES AND PRACTICE OF MEDICINE. 
 Fourth Edition, thoroughly revised and largely rewritten. 8vo, 
 cloth, pp. xvi. 1182, with charts and illustrations. Price 18s. nett. 
 
 %* Many and important changes have been made in this edition. 
 The article on Typhoid Fever has been in great part rewritten, and 
 there is embodied in it the additional experience of my clinic. 
 The subject of Malaria has had to be recast, and the important 
 new matter on etiology and prophylaxis has been added. 
 Dysentery, Yellow Fever, and the Plague have attracted the attention 
 of so many workers that it is difficult to keep pace with the rapid 
 progress of our knowledge. I have tried to bring these articles up 
 to date, and in rewriting them have kept in mind the needs of 
 physicians practising in the tropics. 
 
 Practically new articles, in whole or in part, are these on Acute 
 Tuberculosis, Diseases of the Pancreas, Splenic Anaemia, Arsenical 
 Poisoning, Herpes Zoster, Adiposis Dolorosa, Fibrinous Bronchitis, 
 Albumosuria, Oxaluria, Meniere's Disease, Aphasia, Combined 
 Sclerosis of the Cord, Myasthenia Gravis, Congenital Aneurism, 
 Surgical Treatment of Aneurism and Scurvy. 
 
 LECTURES ON ANGINA PECTORIS AND ALLIED 
 STATES. 8vo, cloth, pp. viii., T6o. Price 6s. nett. 
 
20 CATALOGUE OF MEDICAL PUBLICATIONS 
 
 Parvin, Theophilus, M.D., LL.D., 
 
 Professor of Obstetrics and Diseases of Women and Children in Jefferson Medical 
 College, Philadelphia, and one of the Obstetricians to the Philadelphia Hospital. 
 
 THE SCIENCE AND ART OF OBSTETRICS. Third 
 Edition, thoroughly revised. Large 8vo, cloth, pp. 685, with 269 
 wood engravings and 2 coloured plates. Price 18s. 
 
 Pekelharing, C. A., 
 
 Professor in the Faculty of Medicine, University of Utrecht ; 
 and 
 
 Winkler, C., 
 
 Lecturer in the University of Utrecht. 
 
 BERI-BERI : Researches concerning its Nature and Cause and the 
 Means of its Arrest. Translated by JAMES CANTLIE, M.A., M.B., 
 F.R.C.S. 8vo, cloth, pp. xvi., 160, with coloured illustrations 
 from original drawings. Price 10s. 6d. nett. 
 
 Potter, Samuel O. L., M.D., M.R.C.P. (Lond.), 
 
 Cooper Medical College, San Francisco. 
 
 COMPEND OF HUMAN ANATOMY, Including the Anatomy 
 of the Viscera. Sixth Edition, revised and enlarged. Crown 8vo, 
 cloth, pp. 289, with 117 engravings and 16 full-page plates. 
 Price 5s. 
 
 Schafer, E. A., LL.D., F.R.S., 
 
 Professor of Physiology, University of Edinburgh. 
 
 TEXT -BOOK OF PHYSIOLOGY. By British Physiologists. 
 Edited by E. A. SCHAFER, F.R.S., Professor of Physiology, Uni 
 versity of Edinburgh. 2 vols., royal 8vo. Vol. I., pp. xx., 1036, 
 with 3 plates and 93 illustrations in the text. Price 31s. 6d. 
 Vol. II., pp. xxiv., 1365, with 449 illustrations in the text. Price 
 42s. 
 
 %* The list of contributors is as follows : Professor Sir 
 BURDON SANDERSON (Oxford), Professor GAMGEE, Dr. GASKELL 
 (Cambridge), Professor GOTCH (Oxford), Professor SHERRINGTON 
 (Liverpool), Professor M'KENDRICK (Glasgow), Professor HALLI- 
 BURTON (King's College), Professor HAYCRAFT (Cardiff), Dr. 
 PEMBREY (Guy's), Professor STARLING (University College), J. N. 
 LANGLEY (Cambridge), Professor WAYMOUTH REID (Dundee), 
 B. MOORE (Charing Cross), F. G. HOPKINS (Cambridge), LEONARD 
 HILL (London Hospital), W. H. R. RIVERS (Cambridge), J. S. 
 EDKINS (St. Bartholomew's), A. A. GRAY (Glasgow), D. NOEL 
 PATON (Edinburgh), and the Editor. 
 
ISSUED BY YOUNG J. PENTLAND. 21 
 
 Schech, Philip, M.D., 
 
 Lecturer in the University of Munich. 
 
 DISEASES OF THE MOUTH, THROAT, AND NOSE. 
 Including Rhinoscopy and Methods of Local Treatment. 
 Translated by R. H. BLAIKIE, M.D., F.R.S.E., formerly Surgeon, 
 Edinburgh Ear and Throat Dispensary ; late Clinical Assistant, Ear 
 and Throat Department, Royal Infirmary, Edinburgh. 8vo, cloth, 
 pp. xii., 302, with 5 wood engravings. Price 9s. 
 
 Schmiedeberg, Dr. Oswald, 
 
 Professor of Pharmacology, and Director of the Pharmacological Institute, University 
 of Strassburg. 
 
 ELEMENTS OF PHARMACOLOGY. Translated under the 
 Author's supervision, by THOMAS DIXSON, M.B., Lecturer on 
 Materia Medica in the University of Sydney, N.S.W. 8vo, cloth, 
 pp. xii., 223, with 7 illustrations. Price 9s. 
 
 Sheild, A. Marmaduke, M.B. (Cantab.), 
 F.R.C.S., 
 
 Surgeon and Surgeon in Charge, Throat Department, St. George's Hospital, 
 London. 
 
 SURGICAL ANATOMY: For Students. Crown 8vo, cloth, pp. 
 xii., 226. Price 6s. (Pentland's Students' Manuals.) 
 
 Skene, Alexander J. C., M.D., 
 
 Professor of Gynecology in the Long Island College Hospital, Brooklyn New York. 
 
 MEDICAL GYNECOLOGY: A Treatise on the Diseases of 
 Women from the Standpoint of the Physician. 8vo, cloth, pp. 
 vi., 530, with illustrations in the text. Price 21s. 
 
 Smith, W. Ramsay, M.B., B.Sc., 
 
 Formerly Demonstrator of Anatomy, School of Medicine, Minto House; Late 
 Senior Assistant to the Professor of Natural History, University of Edinburgh. 
 
 EXAMINATION QUESTIONS. Set for the Professional Exam- 
 inations in Edinburgh University during a period of ten years, 
 selected from the Calendars. 
 
 NATURAL HISTORY, arranged and annotated. Price Is. nett. 
 BOTANY, arranged and annotated. Price Is. 6d. nett. 
 CHEMISTRY, answered and annotated. Price 2s. nett. 
 ANATOMY, answered and annotated. Price 2s. nett. 
 
 MATERIA MEDICA AND THERAPEUTICS, answered and 
 annotated. Price 2s. nett. 
 
 PHYSIOLOGY, answered and annotated. Price 2s. nett. 
 
22 CATALOGUE OF MEDICAL PUBLICATIONS 
 
 PATHOLOGY, answered and annotated. Price Is. 6d. nett. 
 
 MIDWIFERY AND GYNAECOLOGY, answered and annotated. 
 Price Is. 6d. nett. 
 
 PRACTICE OF PHYSIC, answered and annotated. Price Is. 6d. 
 nett. 
 
 SURGERY, answered and annotated. Price Is. 6d. nett. 
 
 MEDICAL JURISPRUDENCE AND PUBLIC HEALTH 
 answered and annotated. Price 2s. nett. 
 
 Smith, W. Ramsay, M.B., B.Sc., 
 
 Formerly Demonstrator of Zoology, University of Edinburgh ; 
 and 
 
 Norwell, J. Stewart, B.Sc. 
 
 ILLUSTRATIONS OF ZOOLOGY, INVERTEBRATES AND 
 VERTEBRATES. New and cheaper Edition. Crown 4to, extra 
 cloth, gilt top, with 70 plates exhibiting over 400 figures. Price 
 7s. 6d. 
 
 Snell, Simeon, F.R.C.S.Ed., 
 
 Ophthalmic Surgeon, Sheffield Royal Infirmary; Professor of Ophthalmology, 
 University College, Sheffield. 
 
 A PRACTICAL GUIDE TO THE EXAMINATION OF THE 
 EYE. For Students and Junior Practitioners. Crown 8vo, cloth, 
 pp. xvi., 177, with 88 illustrations in the text. Price 5s. 
 
 Stephenson, Sydney, M.B., F.R.C.S.Ed., 
 
 Surgeon to the Ophthalmic School, Hanwell, London. 
 
 EPIDEMIC OPHTHALMIA : Its Symptoms, Diagnosis, and 
 Management. 8vo, cloth, pp. xvi., 278. Illustrated with a coloured 
 plate and 25 figures in the text. Price 9s. nett. 
 
 Stewart, Sir Thomas Grainger, M.D., LL.D., 
 
 Late Physician in Ordinary to Her Majesty the Queen, for Scotland ; Professor of 
 the Practice of Physic and of Clinical Medicine in the University of Edinburgh. 
 
 LECTURES ON GIDDINESS AND ON HYSTERIA IN THE 
 MALE. Second Edition. Crown 8vo, cloth, pp. x., 89, with 13 
 illustrations. Price 2s. 6d. nett. 
 
 System of Gynecology and Obstetrics. 
 
 By American Authors. Edited by MATTHEW D. MANN, A.M., 
 M.D., Professor of Obstetrics and Gynecology in the Medical 
 Department of the University of Buffalo, N.Y. ; and BARTON 
 COOKE HIRST, M.D., Associate Professor of Obstetrics in the 
 
ISSUED BY YOUNG /. PENTLAND. 23 
 
 University of Pennsylvania ; Obstetrician to the Philadelphia and 
 Maternity Hospitals ; Gynecologist to the Orthopaedic Hospital. 
 In 8 very handsome volumes, royal 8vo, cloth, of about 400 pages 
 each. Fully illustrated with engravings and coloured plates. Price 
 12s. 6d. each nett. For sale by subscription only. 
 
 Talamon, Ch., 
 
 Physician to the Tenon Hospital, Paris. 
 
 APPENDICITIS AND PERITYPHLITIS. Translated from the 
 French by RICHARD J. A. BERRY, M.B., CM., Late President of 
 the Royal Medical Society, Edinburgh. Crown 8vo, cloth, pp. 
 viii., 240. Price 6s. 
 
 Taylor, Robert W., M.D., 
 
 Clinical Professor of Venereal Diseases at the College of Physicians and Surgeons 
 (Columbia College), New York ; Surgeon to Bellevue Hospital, and Consulting 
 Surgeon to City (Charity) Hospital, New York. 
 
 THE PATHOLOGY AND TREATMENT OF VENEREAL 
 DISEASES. Royal 8vo, cloth, pp. 1002. Illustrated with 230 
 engravings in the text and 7 coloured plates. Price 22s. nett. 
 
 Text- Book of Anatomy. By British Teachers. 
 
 See CUNNINGHAM. 
 
 Text- Book on Nervous Diseases. By American 
 Authors. 
 
 See DERCUM. 
 
 Text- Book of Physiology. By British Phy- 
 siologists. 
 
 See SCHAFER. 
 
 Text- Book of Medicine. By British Teachers. 
 
 See GIBSON. 
 
 Text- Book of Pharmacology and Therapeutics. 
 By British and American Teachers. 
 
 See WHITE. 
 
 Thomson, J. Arthur, M.A., 
 
 Regius Professor of Natural History in the University of Aberdeen. 
 
 OUTLINES OF ZOOLOGY. Third Edition, revised and enlarged. 
 Crown 8vo, cloth, pp. xx., 820, with 323 illustrations in the text. 
 Price 15s. (Pentlantfs Students' Manuals.} 
 
24 CATALOGUE OF MEDICAL PUBLICATIONS 
 
 Walley's Practical Guide to Meat Inspection. 
 
 Fourth Edition, rewritten and enlarged by STEWART STOCKMAN, 
 M.R.C.V.S., Professor of Pathology; Lecturer on Hygiene and 
 Meat Inspection, Edinburgh Royal (Dick's) Veterinary College. 
 Post 8vo, cloth, pp. xvi., 296, with 14 coloured plates and 79 
 illustrations in the text Price 10s. 6d. nett. 
 
 Waring, H. J., M.S., B.Sc.(Lond.), F.R.C.S., 
 
 Demonstrator of Operative Surgery, and Senior Demonstrator of Anatomy, St 
 Bartholomew's Hospital ; Senior Assistant Surgeon, Metropolitan Hospital; Surgeon 
 to the Belgrave Hospital for Children, London. 
 
 DISEASES OF THE LIVER, GALL BLADDER, AND 
 BILIARY SYSTEM; their Pathology, Diagnosis, and Surgical 
 Treatment. 8vo, cloth, pp. xvi., 385, with 58 engravings. Price 
 12s. 6d. nett. 
 
 MANUAL OF OPERATIVE SURGERY. Crown 8vo, cloth, pp. 
 xxxii., 662, with 420 illustrations in the text. Price 12s. 6d. 
 
 Warren, Qeo. W., D.D.S., 
 
 Clinical Chief, Pennsylvania College of Dental Surgery. 
 
 COMPEND OF DENTAL PATHOLOGY AND DENTAL 
 MEDICINE. Crown 8vo, cloth, pp. 109. Price 4s. 6d. 
 
 Webster, J. Clarence, B.A., M.D., F.R.C.P.Ed., 
 
 Professor of Midwifery and Diseases of Women in the University of Chicago ; 
 formerly Demonstrator of Gynaecology, M'Gill University ; Assistant Gynaecologist, 
 Royal Victoria Hospital, Montreal ; Assistant to the Professor of Midwifery and 
 Diseases of Women and Children in the University of Edinburgh. 
 
 ECTOPIC PREGNANCY : its Etiology, Classification, Embryology, 
 Diagnosis, and Treatment. 8vo, cloth, pp. xvi., 240, with 22 pages 
 of plates and 15 figures throughout the text. Price 12s. 6d. nett. 
 
 RESEARCHES IN FEMALE PELVIC ANATOMY. Demy 4 to, 
 cloth, gilt top, xiv., 129. Illustrated with 26 full-page coloured 
 plates, from original drawings. Price 30s. nett. 
 
 TUBO-PERITONEAL ECTOPIC GESTATION. Demy 4 to, 
 cloth, gilt top, pp. xii., 54. Illustrated with n full-page plates, 
 exhibiting numerous figures, mostly coloured. Price 16s. nett. 
 
 PRACTICAL AND OPERATIVE GYNECOLOGY. Crown 8vo, 
 cloth, pp. xvi., 295. Illustrated with 54 engravings. Price 7s. 6d. 
 
 DISEASES OF WOMEN. A Text-Book for Students and Prac- 
 titioners. Crown 8vo, cloth, pp. xxiv., 688, with 241 illustrations. 
 Price 14s. 
 
ISSUED BY YOUNG J. PENTLAND. 25 
 
 White, W. Hale, M.D., F.R.C.P., 
 
 Physician and Lecturer on Medicine, Guy's Hospital, London. 
 
 TEXT-BOOK OF PHARMACOLOGY AND THERAPEUTICS. 
 Edited by W. HALE WHITE, M.D., F.R.C.P. Royal 8vo, extra 
 cloth, pp. xvi., 1016. Price, 21s. nett. 
 
 *#* The list of contributors is as follows : J. ROSE BRADFORD, 
 J. H. BRYANT, J. THEODORE CASH, A. R. CUSHNY, WALTER 
 DIXON, M. G. FOSTER, A. E. GARROD, J. S. HALDANE, H. 
 AMORY HARE, L. E. HILL, F. G. HOPKINS, The Late D. J. 
 LEECH, E. W. LUCAS, HECTOR MACKENZIE, C. R. MARSHALL, 
 SIDNEY MARTIN, THOMAS OLIVER, M. S. PEMBREY, G. VIVIAN 
 POORE, G. ROWELL, G. H. SAVAGE, JOHN V. SHOEMAKER, 
 S. E. SOLLY, W. G. SMITH, RALPH STOCKMAN, NESTOR 
 TIRARD, J. W. WASHBOURN, W. HALE WHITE, R. B. WILD. 
 
 Williamson, Richard T., M.D., F.R.C.P., 
 
 Physician, Ancoats Hospital ; Assistant Lecturer on Medicine, Owens College, 
 Manchester. 
 
 DIABETES MELLITUS AND ITS TREATMENT. 8vo, cloth, 
 pp. xvi., 417, with 18 illustrations (two coloured). Price 
 12s. 6d. nett. 
 
 Winckel, Dr. F., 
 
 Professor of Gynaecology and Director of the Royal Hospital for Women ; Member 
 of the Supreme Medical Council and of the Faculty of Medicine in the University 
 of Munich. 
 
 TEXT-BOOK OF OBSTETRICS, including the Pathology and 
 Therapeutics of the Puerperal State. Designed for Practitioners 
 and Students of Medicine. Translated from the German under 
 the supervision of J. CLIFTON EDGAR, A.M., M.D., Adjunct Pro- 
 fessor of Obstetrics in the Medical Department of the University of 
 the City of New York. Royal 8vo, cloth, pp. 927. Illustrated with 
 190 engravings, mostly original. Price 28s. 
 
 Woodhead, G. Sims, M.D., F.R.C.P.Ed., 
 
 Professor of Pathology, University of Cambridge. 
 
 PRACTICAL PATHOLOGY : A Manual for Students and Practi- 
 tioners. Third enlarged and thoroughly revised Edition. 8vo, cloth, 
 pp. xxiv., 652, with 195 coloured illustrations, mostly from original 
 drawings. Price 25s. 
 
 Woodhead, G. Sims, M.D., F.R.C.P.Ed., 
 
 and 
 
 Hare, Arthur W., M.B., C.M. 
 
 PATHOLOGICAL MYCOLOGY : An Enquiry into the Etiology 
 of Infective Diseases. Section i. Methods. 8vo, cloth, pp. xii., 
 174, with 60 illustrations, mostly original (34 in colours). Price 
 8s. 6d. 
 
26 
 
 CATALOGUE OF MEDICAL PUBLICATIONS 
 
 CLASSIFIED INDEX. 
 
 Abdominal Surgery, . 
 
 Abscesses (Treatment), 
 Anatomy (Practical), . . 
 
 (Text-Book), . ' . 
 
 (Compend of), . f , 
 
 (Surgical), 
 
 (Examination Questions), 
 
 (Female Pelvic), 
 Angina Pectoris, . . 
 
 Appendicitis, 
 Aseptic Surgery, . 
 Atlases (Brain), . 
 
 (Eye), .. 
 (Skin), . 
 
 (Venereal Diseases), 
 
 KEITH. 
 
 CHEYNE. 
 
 CUNNINGHAM. 
 
 CUNNINGHAM. 
 
 POTTER. 
 
 SHEILD. 
 
 SMITH. 
 
 WEBSTER. 
 
 OSLER. 
 
 TALAMON. 
 
 LOCKWOOD. 
 
 BRUCE. 
 
 FROST. 
 
 CROCKER. 
 
 MACLAREN. 
 
 Bacteriology, 
 
 j> . 
 
 and Pathology, Journal of. 
 
 Beri-Beri, . . . 
 
 Bones and Joints (Disease of), . 
 Botany (Text-Book), 
 (Manual), 
 
 (Examination Questions), . 
 Brain (Tumours), . 
 
 (Illustrations of Nerve Tracts), 
 
 MUIR & RITCHIE. 
 WOODHEAD & HARE 
 
 PEKELHARING. 
 
 CHEYNE. 
 
 BEHRENS. 
 
 JOHNSTONE. 
 
 SMITH. 
 
 BRAMWELL. 
 
 BRUCE. 
 
 Chemistry (Examination Questions), 
 Children (Diseases), 
 
 (Compend of Diseases), . 
 
 (Treatment of Diseases), 
 Clinical Gynaecology, . 
 Medicine 
 
 SMITH. 
 
 CARMICHAEL. 
 
 HATFIELD. 
 
 MUSKETT. 
 
 KEATING & COE. 
 ANDERSON. 
 GIBSON & RUSSELL. 
 
ISSUED BY YOUNG /. PENTLAND. 
 
 27 
 
 Clinical Medicine, 
 
 MUSSER. 
 
 Dental Pathology, 
 Dermatology (Atlas), 
 
 Diabetes Mellitus, 
 Diagnosis (Ophthalmoscopic), 
 
 (Physical), 
 (Medical), 
 Dictionary of Terms (5 languages), 
 
 Diet, 
 
 WARREN. 
 
 CROCKER. 
 
 JAMIESON 
 
 MORROW. 
 
 WILLIAMSON. 
 
 BERRY. 
 
 GIBSON & RUSSELL. 
 
 MUSSER. 
 
 BILLINGS. 
 
 KEATING. 
 
 BRUEN. 
 
 Ear (Diseases), 
 
 ... 
 
 Ectopic Gestation, 
 Edinburgh Medical Journal. 
 Epidemic Ophthalmia, 
 Epilepsy, .... 
 Examination Questions, . 
 Eye (Diseases), . 
 
 (Atlas), 
 
 (Diseases), 
 
 (Examination of), 
 
 (Epidemic Ophthalmia), 
 
 (Toxic Amblyopias), . 
 
 Genito-Urinary Diseases, . 
 
 Geographical Pathology, . . 
 
 Gestation (Ectopic), 
 
 Giddiness, 
 
 Gynaecological Operations, 
 
 Gynaecology (Text-Book), . 
 
 (Medical), 
 
 (Examination Questions), 
 
 (Practical), 
 
 (Manual), 
 
 and Obstetrics (System of), 
 
 BURNETT. 
 M 'BRIDE. 
 WEBSTER. 
 
 STEPHENSON. 
 
 ALEXANDER. 
 
 SMITH. 
 
 BERRY. 
 
 FROST. 
 
 NORRIS & OLIVER. 
 
 SNELL. 
 
 STEPHENSON. 
 
 DE SCHWEINITZ. 
 
 MORROW. 
 
 DAVIDSON 
 
 WEBSTER. 
 
 STEWART. 
 
 KEITH. 
 
 KEATING & COE. 
 
 SKENE. 
 
 SMITH. 
 
 WEBSTER. 
 
 jj 
 MANN & HIRST. 
 
 Heart (Diseases), . 
 (Mitral Murmurs), 
 (Movement) 
 
 BRAMWELL. 
 
 BROCKBANK. 
 
 MACKENZIE. 
 
28 CATALOGUE OF MEDICAL PUBLICATIONS 
 
 Heart (Diseases), .... GIBSON. 
 
 (Angina Pectoris), . . . OSLER. 
 
 Hernia, ..... LOCKWOOD. 
 
 Human Monstrosities, . . . HIRST & PIERSOL. 
 
 Hydatid Disease, .... GRAHAM. 
 
 Hygiene and Diseases of Warm Climates, . DAVIDSON. 
 
 Hysteria, ..... STEWART. 
 
 Infective Diseases, . . . . LOCKWOOD. 
 
 Intracranial Tumours, . . B RAM WELL. 
 
 Involution of Life, . . . MAGUIRE. 
 
 Joints (Tuberculous Disease), . . CHEYNE. 
 
 Journal of Pathology. 
 
 (Edinburgh Medical). 
 Jurisprudence, Medical (Examination Questions), SMITH. 
 
 Kidney (Renal Growths), . . . ,' KELYNACK. 
 
 Lead Poisoning, . . . , OLIVER. 
 
 Life, Involution of, . . . MAGUIRE. 
 
 Liver (Diseases of), . . . WARING. 
 
 Malignant Disease of Throat and Nose, . NEWMAN. 
 
 Materia Medica (Examination Questions), . SMITH. 
 
 Meat Inspection, . . . . WALLEY. 
 
 Medical Diagnosis, . . . MUSSER. 
 
 Dictionary (5 languages), . . BILLINGS. 
 
 . . KEATING. 
 
 Gynaecology, . . . SKENE. 
 
 Jurisprudence (Examination Questions), SMITH. 
 
 Medicine (Clinical) . . . ANDERSON. 
 
 Medicine (Text-Book of), . . ' . GIBSON. 
 
 (Text-Book of), . . . OSLER. 
 
 (Examination Questions), . SMITH. 
 
 Midwifery (Treatise on), . . . DAVIS. 
 
 (Compend of), ,'V . LANDIS. 
 
 (Manual of), . . ' . . ' MURRAY. 
 
 (Text-Book), . . , PARVIN. 
 
 (Examination Questions), . SMITH. 
 
 (System of), . . . MANN & HIRST. 
 
 (Text-Book of), . . WINCKEL. 
 
 Mitral Murmurs, . . . . BROCKBANK. 
 
 Monstrosities (Human), . . . HIRST & PIERSOL. 
 
ISSUED BY YOUNG /. PENTLAND. 
 
 29 
 
 Morbid Anatomy, 
 
 Mouth, Throat and Nose (Diseases), 
 
 Natural History (Examination Questions), 
 (Illustrations), 
 
 (Text-Book), 
 
 Nervous Diseases (Epilepsy), . ^ . 
 (Text-Book), . 
 
 (Nursing), 
 
 Nervous System and Visceral Disease, 
 Nose (Diseases), .... 
 
 (Diseases), . 
 
 Nose and Throat (Malignant Disease of), . 
 Nursing (Obstetric), 
 (Insane), . 
 
 HALL. 
 SCHECH. 
 
 SMITH. 
 
 SMITH & NORWELL. 
 
 THOMSON. 
 
 ALEXANDER. 
 
 DERCUM. 
 
 MILLS. 
 
 MILLS. 
 
 MORISON. 
 
 McBRIDE. 
 
 SCHECH. 
 NEWMAN. 
 
 HAULTAIN & FERGUSON. 
 MILLS. 
 
 Obstetric Nursing, . 
 Obstetrics (Text-Book of), 
 
 (Compend of), . 
 
 (Manual of), 
 
 (Science and Art of), 
 
 ,, (System of), 
 
 (Text-Book of), 
 Ophthalmia (Epidemic), . 
 Ophthalmology (Text-Book of), . 
 Ophthalmoscopic Diagnosis, 
 Ophthalmoscopy (Atlas of), . CT 
 
 Parasites of Man, . 
 
 Pathological Mycology, 
 
 Pathology (Examination Questions), 
 
 (Geographical), . 
 (Practical), 
 
 (Compend of), . 
 (Dental), 
 
 (Practical), 
 
 (Thyroid Gland), 
 Pathology and Bacteriology (Journal of). 
 Pediatrics, 
 
 Pharmacology, 
 
 (Text-Book), 
 
 HAULTAIN & FERGUSON. 
 DAVIS. 
 LANDIS. 
 MURRAY. 
 PARVIN. 
 
 MANN & HIRST. 
 WINCKEL. 
 STEPHENSON. 
 NORRIS & OLIVER. 
 BERRY. 
 FROST. 
 
 LEUCKART. 
 
 WOODHEAD & HARE. 
 
 SMITH. 
 
 DAVIDSON. 
 
 GIBBES. 
 
 HALL. 
 
 WARREN. 
 
 WOODHEAD. 
 
 EDMUNDS. 
 
 CARMICHAEL. 
 HATFIELD. 
 MUSKETT. 
 SCHMIEDEBERG. 
 HALE WHITE. 
 
30 CATALOGUE OF MEDICAL PUBLICATIONS 
 
 Physical Diagnosis, 
 
 Physiology (Examination Questions), 
 
 (Text-Book), . . . 
 
 Poisoning (Lead), .... 
 Practice of Medicine (Text-Book of), 
 (Text-Book of), 
 
 (Exam. Questions), . 
 
 Pregnancy (Ectopic), . . . \ 
 
 Prescribing and Treatment of Children's Diseases, MUSKETT. 
 Pulse, . . . . . MACKENZIE. 
 
 GIBSON & RUSSELL. 
 
 SMITH. 
 
 SCHAFER. 
 
 OLIVER. 
 
 GIBSON. 
 
 OSLER. 
 
 SMITH. 
 
 WEBSTER. 
 
 Renal Growths, 
 
 KELYNACK. 
 
 Septic Diseases, . 
 Sexual Organs (Diseases), 
 Skin Diseases (Atlas of), 
 
 Stomach (Diseases), 
 Surgery (Abdominal), 
 
 (Aseptic), 
 
 (Examination Questions), 
 
 (Operative), 
 Surgical Anatomy, 
 Syphilology, 
 
 ,, ... 
 
 System of Genito Urinary Diseases, 
 
 Gynaecology and Obstetrics, 
 
 Therapeutics, . 
 
 CHEYNE. 
 
 FULLER. 
 
 CROCKER. 
 
 JAMIESON. 
 
 MORROW. 
 
 MARTIN. 
 
 KEITH. 
 
 LOCK WOOD. 
 
 SMITH. 
 
 WARING. 
 
 SHEILD. 
 
 MORROW. 
 
 TAYLOR. 
 
 MORROW. 
 
 MANN & HIRST. 
 
 HARE. 
 
 Teratology, . 
 
 Therapeutics (Synopsis), . 
 
 (Principles of Treatment) 
 
 (System), . 
 
 (Physical and Natural), 
 
 (Examination Questions) 
 
 (Text-Book), 
 
 Throat (Diseases), 
 
 and Nose (Malignant Disease of), . 
 Nose and Ear (Diseases), . 
 Thyroid Gland (Pathology and Diseases of), 
 Toxic Amblyopias, 
 Traumatic Infection, 
 
 HIRST & PIERSOL. 
 
 AITCHISON. 
 
 BRUCE. 
 
 HARE. 
 
 HAYEM & HARE. 
 
 SMITH. 
 
 HALE WHITE. 
 
 SCHECH. 
 
 NEWMAN. 
 
 McBRIDE. 
 
 EDMUNDS. 
 
 DE SCHWEINITZ. 
 
 LOCKWOOD. 
 

 ISSUED BY YOUNG J. PENTLAND. 31 
 
 Treatment (Principles of), . . BRUCE. 
 
 Tropical Diseases, .... DAVIDSON. 
 
 Tumours (Intracranial), . . . BRAMWELL. 
 
 Ulcers (Treatment), . . . CHEYNE. 
 
 Urine, . . . . . HOLLAND. 
 
 Venereal Diseases, . . . MACLAREN. 
 
 ... MORROW. 
 
 ... TAYLOR. 
 
 Visceral Disease and Nervous System, . MORISON. 
 
 Warm Climates (Diseases), . . DAVIDSON. 
 
 Women (Diseases of), . . . KEATING & COE. 
 
 (Diseases), . . . SKENE. 
 
 (Diseases of), . . . WEBSTER. 
 
 Wounds (Treatment), . . . CHEYNE. 
 
 Zoology (Examination Questions), . SMITH. 
 
 (Illustrations of), . . . SMITH & NORWELL. 
 
 (Outlines of), . , . . THOMSON. 
 
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